16. Genus — CATOPHRAGMUS. Pl. 20.

CATOPHRAGMUS. G. B. Sowerby. Genera of Recent and Fossil Shells. Plate.

Interior compartments eight, with several exterior whorls of small supplemental compartments: basis either membranous or calcareous.

Distribution, West Indies and Australia. Attached to littoral shells and rocks.

This genus is very remarkable amongst sessile cirripedes, from the eight normal compartments of the shell being surrounded by several whorls of supplemental compartments or scales: these are arranged symmetrically, and decrease in size but increase in number towards the circumference and basal margin. A well preserved specimen has a very elegant appearance, like certain compound flowers, which when half open are surrounded by imbricated and graduated scales. The Chthamalinæ, in the structure of the mouth and cirri, and to a certain extent in that of the shell, fill up the interval between the Balaninæ and Lepadidæ; and Catophragmus forms, in a very remarkable manner, the transitional link, for it is impossible not to be struck with the resemblance of its shell with the capitulum of Pollicipes. In Pollicipes, at least in certain species, the scuta and terga are articulated together — the carina, rostrum, and three pairs of latera, making altogether eight inner valves, are considerably larger than those in the outer whorls — the arrangement of the latter, their manner of growth and union, — all are as in Catophragmus. If we, in imagination, unite some of the characters found in the different species of Pollicipes, and then make the peduncle so short (and it sometimes is very short in P. mitella) that the valves of the capitulum should touch the surface of attachment, it would be impossible to point out a single external character by which the two genera in these two distinct families could be distinguished: but the more important differences in the arrangement and nature of the muscles which are attached either to the opercular valves or surround the inside of the peduncle, would yet remain.

Although all the valves of the shell, even the eight in the innermost whorl, are very thin, yet from their number in the successive whorls, and from each being concave inwards, so as to form a cavity or tube into which the corium enters, the total thickness of the sides of the shell is very considerable. Both of the species of Catophragmus occurred mingled, in the one case with Tetraclita porosa and in the other with T. purpurascens; now the walls of these shells, we know, are very thick, and are permeated by several rows of pores, occupied by threads of corium; seeing this, we may be permitted to believe, that the several exterior whorls of valves in Catophragmus, between which the corium is prolonged for some way upwards, are of service to the animal, by thickening its shell, in an analogous, but not homologous, manner, as in Tetraclita.

Considering the whole structure, external and internal, of Catophragmus, with the one great exception of the exterior whorls of valves, there is hardly a single generic character by which it can be separated from Octomeris and Pachylasma; indeed, I am not quite sure that it would not have been better to have run these three genera together.

Of the two species, I will first describe C. polymerus, and not the C. imbricatus of Sowerby, inasmuch as I have plenty of excellent specimens of the former, whereas the original specimens of C. imbricatus, in the British Museum, consist of one old and not perfect shell, without the opercular valves or the included animal’s body; and the other, though quite perfect, far from mature. As far as these materials allow of minute comparison, the whole shell, with the exception of the basis, and the opercular valves agree very closely in the two species, whereas the included animal’s body differs more than is usual in nearly related species; — thus, C. imbricatus has caudal appendages, of which there is no trace in C. polymerus, and I have seen only one other instance in which this organ was absent in one species (Scalpellum villosum) and present in the other species of the same genus. Under these circumstances it will be most convenient first to describe in detail C. polymerus, and then only indicate the points of difference in C. imbricatus.

 

1. CATOPHRAGMUS POLYMERUS. Pl. 20, fig. 4 a-4 e.

Basis membranous: caudal appendages none.

Hab. — New South Wales (Twofold Bay), Mus. Darwin; Swan River (?), Mus. Cuming. Attached to littoral rocks and shells, and associated with Tetraclita purpurascens, Balanus nigrescens, Chthamalus antennatus, Chamæsipho columna.

General Appearance. — Shell nearly circular, moderately or slightly depressed; colour gray. The eight normal compartments of the inner whorl are two or three times as large as those in the second whorl; the other smaller compartments or scales graduate very regularly in size, to mere beads, at the extreme basal edge, and are arranged symmetrically. The general aspect of the shell depends chiefly on the degree to which the surface has been disintegrated, and differs greatly in the two extreme states. When well preserved, the general appearance is very elegant; the scales are all neatly imbricated; they terminate upwards in points, but with their extreme tips generally broken; from laterally overlapping each other, their external surfaces (as seen, when corroded, in fig. 4 d, or when slightly exposed after the continued growth of their basal margins, in fig. 4 a) become longitudinally keeled, often with a secondary ridge or shoulder on one side; they are, also, crossed by rather conspicuous and regular lines of growth, or more strictly, former lines of union between the several valves: the orifice of the shell in this perfect condition is sub-rhomboidal and notched, and the scuta are united to the terga by nearly straight sutures. On the other hand, when the shell has been considerably corroded, and this seems to be the more common condition, the appearance is not elegant: the scales in the successive whorls are not imbricated, but owing to their upper parts having been worn down, they present a tesselated surface (4 d), with the tesseræ graduated in size, and of a peculiar shape, namely, a rectangle, with a more or less broad square projection on the exterior side, together often with a large square notch on one or both corners, caused by their laterally overlapping each other. Some of the shells are so deeply corroded, that no portion of the original surface is preserved, excepting the lowermost bead-like scales; and the whole shell has so rugged an aspect, that the successive whorls of the worn-down valves might easily be overlooked. In the corroded specimens, the orifice approaches to circular in outline, and is large and nearly entire: the scuta and terga are deeply interlocked together. The largest specimen which I have seen was one inch and a quarter in basal diameter.

Structure of the Shell. — The eight inner normal compartments are not thicker than the outer valves, and are far thinner than in ordinary sessile cirripedes. They are arranged as in Octomeris. The lateral compartments are broader than the rostro-lateral and carino-lateral compartments. The shelly laminæ, of which these compartments and the opercular valves are composed, alternate with yellow membranous layers, exactly as is the case with Octomeris. The lateral edges of the compartments, beneath the alæ, in the six compartments having alæ, bend inwards, especially just above the basis, so that the compartments in their lower parts (fig. 4 c) stand much more separate than is usual. The basal edge of each is irregularly toothed. The sheath presents no particular character. The eight compartments have longitudinal shoulders and ribs on their external surfaces, caused by the lateral overlapping and pressure of the exterior scales. They are also marked by slight, transverse or oblique calcareous ridges, caused by the attachment of the membrane, by which they are united to the smaller compartments or scales outside them. A new line of attachment, and consequently a new ridge is formed, lower and lower down at each period of growth, as the shell is added to at the basis, — in the same manner as new ridges are added to the lower edge of the sheath at each period of growth. The shell, excepting in old worn-down specimens, increases largely by diametric growth: during the diametric growth, the outer scales must be laterally separated a little from each other, and probably they are laterally added to; but there are no distinct lines of suture, or rows of smaller scales, corresponding with the sutures between the eight inner compartments. The alæ do not project much; their edges, as well as the shoulders into which they fit, are generally irregularly crenated: they are added to during diametric growth above the line of attachment of the opercular membrane. There is no appearance of radii; but as the eight inner compartments are added to laterally, and are often crenated, on the edges which correspond with the radii in other Cirripedes, such edges must be considered as radii.

With respect to the scales in the several outer whorls, they resemble each other except in size, and the outermost scales are reduced to mere transversely elongated beads. Their basal edges are concave inwards, being bent like the ridge of a house; hence sub-triangular spaces or tubes, lined by the corium, run up between the scales. When perfectly preserved, the outline of each scale is a much elongated triangle, but usually, from their summits having been worn off, the outline is nearly that of a parallelogram. Their basal edges are dentated, and their upper parts, both on the outside and inside, are marked, where joined to the other compartments, by slight calcareous ridges: outside, there are longitudinal shoulders (Pl. 20, fig. 4 b), caused by the lateral overlapping of the adjoining scales; these are best seen in section in corroded specimens (fig. 4 d): on the inside there are, also, in the upper part, slight medial longitudinal ridges, caused by the sutures, which the scales have covered.

In large old specimens there are ten, or even more, whorls of compartments, but it is scarcely possible to count them with any accuracy. The first whorl consists of the eight large inner compartments, though, homologically, it is doubtful whether the rostro-lateral compartments in any sessile cirripede really belong to the same whorl with the others. The second whorl consists of eight smaller pieces, covering the eight sutures in the first whorl (see the tracing of the basal edges of all the compartments and valves in a very perfect specimen, Pl. 20, fig. 4 c). The third whorl, in large and perfect specimens, consists of twice the number, or sixteen, still smaller scales, corresponding with the sixteen sutures of the second whorl; but sometimes there are less than sixteen pieces, owing to some of the scales being large enough to cover two adjoining sutures as well as the intermediate portion of the compartments of the first whorl. In the fourth whorl, instead of there being, even in the most perfect specimens, twice sixteen, or thirty-two pieces, there are only twenty-four; this being caused by single pieces (placed alternately with two pieces) being broad enough to cover two sutures as well as the intermediate portion of the compartment of the third whorl. In the succeeding whorls this same arrangement seems to be the usual one, so that in the fifth whorl, instead of there being, in the most perfect specimens, twice twenty-four, or forty-eight pieces, that is, twice the number in the last whorl, there are only thirty-six scales, or once and a half as many scales.

 

The Basis is thin and membranous; it firmly adheres to the surface of attachment.

Scuta, nearly flat: the articular ridge is very prominent, and there is a deep articular furrow both above and below; but the precise outline of the ridge and furrows varies: there is a pit for the adductor muscle, but no crests or marks for the other muscles. The Terga are remarkable from the extreme prominence of the articular ridge and depth of the articular furrow. The basal margin viewed internally seems straight, so that there appears to be no spur; but viewed externally, when the crests for the depressor muscles are seen to depend considerably beneath the true basal margin, a slight, very broad spur may be perceived to exist. These depending crests for the muscles are rather thin, but they extend over half the basal margin of the valve.

Mouth. — The labrum is very bullate, being as long in its longitudinal axis as the rest of the mouth: crest hairy, with some very minute teeth. Palpi truncated, with their apices not nearly touching each other; thickly clothed with spines. Mandibles with three large single teeth, of which the lower one has a single fine tooth at its upper basal edge, showing a tendency to become pectinated; inferior part short, coarsely pectinated. Maxillæ notched, with a slight second notch and slight double prominence in the lower part.

Cirri. — First and second pairs short, with the rami in each unequal in length by about four segments; on both rami in the second cirrus, and in the shorter ramus of the first cirrus, there are some coarsely pectinated spines. All four posterior cirri are alike; the segments bear five pairs of strong spines, with a large intermediate tuft of fine spines: the dorsal tuft is also large, consisting of short thick, and long finer spines. There is no vestige of caudal appendages, though present in the succeeding species.

Branchiæ moderately large, in area equalling the prosoma; surface not plicated.

 

2. CATOPHRAGMUS IMBRICATUS.

CATOPHRAGMUS IMBRICATUS. G. B. Sowerby. Genera of Recent and Fossil Shells, Plate.

Basis calcareous: caudal appendages present.

Hab. — Antigua, West Indies, attached to a Tetraclita porosa.

As stated under the genus, this species is known from two specimens in the British Museum, one of which is full-sized, being three quarters of an inch in diameter, but is destitute of the outermost whorls, of the basis, opercular valves, and animal’s body; the other is perfect, but very young, being barely two tenths of an inch in basal diameter. As far as the characters can be made out from these materials, I can perceive no difference from C. polymerus in the shell, excepting that in the small specimen of C. imbricatus, there would appear to exist fewer whorls. The opercular valves are likewise closely similar: in the scuta, however, of the young specimen in the present species, the articular ridge seems to be a little broader, but this is so variable a character that no confidence can be placed in it: these valves, moreover, externally have a broad furrow along the middle, running from the apex to the basal margin, which is not the case with the scutum of C. polymerus; but then I have often seen, in young specimens of Balanus, a similar furrow, which is quite absent in full-grown specimens. When we come to the basis we find a good diagnostic character, for here it is calcareous: it is rather thin, solid, and white; towards the outside it is pitted with small cavities, corresponding with the small teeth on the basal edges of the compartments. The latter adhere firmly to the basis. The central internal surface is covered by an irregular network of imbedded cement-ducts, some of which bifurcate. From the description here given, it will be seen that any figure would have been superfluous, the last species having been so well illustrated.

Mouth. — I can point out no difference, excepting that the palpi are here more oval or less truncated at their ends; and that the lower corner of the maxillæ seems to be more prominent. In the Cirri, the rami of the first and second pairs are nearly equal in length: none of the spines are coarsely pectinated. In the four posterior pairs of cirri, instead of a tuft of small spines on each segment between the pairs of main spines, there are only a few minute intermediate spines: the dorsal tufts are also here smaller, but are, as in the last species, composed of short thick, and longer thinner spines.

Caudal Appendages. — This is the only species of sessile cirripede, with the exception of the two species of Pachylasma, which possesses these organs: they are situated on each side of the anus in the usual position: they are minute, equalling in length only the lower segment of the pedicel of the sixth cirrus: in a specimen in which the rami of the sixth cirrus had eighteen or twenty segments, these appendages consisted of only three tapering segments, supporting a few thick spines.

Branchiæ. — I believe I discovered these, consisting of two minute pouches, placed at the carinal end of the sack: if this observation be correct, this species differs from C. polymerus in the much smaller size of these organs.

 

 

REMARKS ON BRONN’S LIST OF FOSSIL BALANINÆ AND CHTHAMALINÆ.

The following species of fossil Balanidæ are given in that most useful work, the ‘Enumerator Palæontologicus’ in Bronn’s ‘Gesichte der Natur:’ it has appeared to me that a few words on each species, might hereafter save others the trouble of searching through several works.

Tubicinella maxima of Morren, said to have been found in the Chalk: this would have been a wonderful fact, considering that no true sessile cirripede has hitherto been found in this formation, and that it implies the existence of Cetacea at this period; but I have been informed that the fossil in question is not a Cirripede.

Diadema bifidum = Coronula bifida of Bronn, in his ‘Italiens Tertiär-Gebilde’ (1831),  (no Plate). Without a much fuller description I can form no judgment on this species.

Diadema vulgare is probably the Coronula barbara, a Crag fossil described by me.

Pyrgoma undata, Michelotti, in ‘Bull. Soc. Geolog.’ tom. x, , a mere name without any description: probably it is a synonym of

Pyrgoma sulcatum, Philippi, ‘Enum. Mollusc. Siciliæ,’ which is a synonym of Pyrgoma Anglicum of the present work; found recent and fossil.

Acasta Montagui is probably the extinct Acasta undulata described by me.

Chthamalus giganteus of Philippi, is the Pachylasma giganteum of this work; found recent and fossil.

Chthamalus stellatus, said by Philippi to be found fossil in Sicily; such may be the case, but the littoral habits of the species do not render it very probable.

Balanus carbonarius of Petzholdt, found in the Carboniferous formation! but I have given my reasons, in my ‘Monograph on the Fossil Lepadidæ,’ , for disbelieving that this is a Balanus, or even a Cirripede.

Balanus ostrearum appears to be a mere name by Conrad, published by Morton in his ‘Synopsis of the Organic Remains of the Cretaceous Group,’ 1834, Appendix, .

Balanus peregrinus is briefly described and poorly figured, without the opercular valves, by Morton, in his ‘Synopsis,’ ut supra, , Pl. 10, fig. 5: this Eocene species apparently resembles the Eocene B. unguiformis of Sowerby, described in this work; but quite indispensable details of structure for identification are not given. Another figure of this shell is given in the ‘American Journal of Science’ (N. S.), vol. i, Pl. 2, fig. 6.

Balanus circinnatus, communis, and pustula, of Defrance, as well as all the other species named by him, are described so imperfectly, that the descriptions are of no value whatever, every description being applicable to every species: I must add, that the B. communis is not the B. communis of British authors, a name applied to several forms.

Balanus Finchii is briefly described and figured, but without the opercular valves, by Isaac Lea, in his ‘Contributions to Geology,’ 1833, , Pl. 6, fig. 222. I do not think that I have seen this species.

Balanus Holgeri, Geinitz, ‘Grundriss der Versteinerungen,’ tab. ix, fig. 19. No opercular valves are given; this species cannot be even approximately recognised.

Balanus proteus, Conrad, ‘Fossil Shells of Miocene Formation of U. States,’ , Pl. 44 (in ‘Journal Acad. Nat. Sc.,’ Phil., vol. vii, ). I cannot recognise this species; it resembles B. porcatus; but as the radii are rather narrow, and apparently with slightly oblique summits, it may be B. concavus; the opercular valves are not figured.

Balanus sagittata is merely a provisional name without any description, given in a paper on the Crag by S. Woodward, in the ‘London and Edin. Philosoph. Magazine, Brewster, Taylor, and Phillips,’ vol. vii, July-December, 1835, .

Balanus sublævis, J. de C. Sowerby, in ‘Geolog. Trans.,’ 2d series, vol. v, Pl. 25, fig. 3. Plate extremely imperfect; description extremely short and useless; a species from India not to be recognised.

Balanus balanoides; the species thus named by Ranzani, and found by Philippi in Sicily, certainly is not the true Lepas balanoides of Linn., but may be B. amphitrite of this work. In British collections of Crag specimens I have found the B. dolosus (nov. spec.) thus named: I much doubt whether the truly littoral B. balanoides of Linnæus has been found fossil.

B. costatus of Montagu, a synonym of B. sulcatus of Bruguière, and of B. porcatus of this work; found fossil and recent. This species was originally described by Linnæus under the name of Lepas balanus. But the fossil Lepas balanus of Brocchi is a different species; if it be the same with the recent Lepas balanus of Poli, then it is the B. perforatus of the present work. Again, the B. sulcatus of Bronn, in his ‘Lethæa Geognostica’ (tab. 36, fig. 14), is quite different from the B. sulcatus of Bruguière (i. e., B. porcatus of the present work), as is at once obvious from the oblique summits of the radii. Lastly, B. tesselatus of Sowerby is a synonym of B. porcatus, sulcatus, costatus, and Lepas balanus.

B. punctatus of Montagu is a synonym of Chthamalus stellatus, see remarks on that species: the name of B. punctatus is often applied by British authors to varieties of B. balanoides, see remarks on that species.

B. rugosus of Morris’s ‘Catalogue’ is a synonym of B. crenatus; found recent and fossil.

B. sulcatus of Bruguière, a synonym of B. porcatus; found recent and fossil: see remarks under B. costatus.

B. tintinnabulum of Linn., found recent and fossil; but no trust whatever ought to be placed in the identifications of this species given in several works; thus the Lepas tintinnabulum of Brocchi is distinct. The B. crassus of Sowerby is the true B. tintinnabulum. The B. fasciatus of Dujardin (perhaps only a MS. name) probably is also this species. The B. crispatus is only a variety of B. tintinnabulum.

B. dentiformis, Defrance: see B. circinnatus.

B. ornatus, Münster, ‘Beiträge zur Petrifact.,’ B. 3, , tab. vi (1840). No opercular valves or details of structure of the several species of Balanus named by Münster, are given, and consequently none can be recognised with certainty.

B. concavus of Bronn, fully described in this work, with the synonyms given; recent and fossil.

B. crassus of Sowerby, a synonym for B. tintinnabulum.

B. latiradiatus, Münster, probably a synonym of B. tintinnabulum, see remarks under B. ornatus.

B. pectinarius, Bronn (‘Italiens Tertiär-Gebilde,’ ), does not appear to me fully enough described to be recognised.

B. pictus of Münster, possibly a synonym of B. amphitrite: see remarks under B. ornatus and balanoides.

B. plicarius, Bronn: see remarks under B. pectinarius.

B. porosus of Hausman (according to Münster of Blumenbach). I cannot recognise this species in Münster’s ‘Beiträge.’

B. pustularis of Lamarck, ‘Animaux sans Vertèbres.’ Scarcely one of the fossil species of Balanus, described by Lamarck, can be recognised; the descriptions are extremely imperfect. There is a figure of B. pustularis in Münster’s ‘Beiträge,’ which makes me think that this may be a synonym of B. concavus of Bronn.

B. pyramidalis, Münster: see remarks under B. ornatus.

B. rhomboicus, Bronn: see remarks under B. plicarius.

B. squamosus, Defrance: see remarks under B. circinnatus.

B. stellaris, Bronn (‘Lethæa Geognostica,’ tab. 36, fig. 13). To this species, Lepas stellaris (I presume a misprint for stellata) of Poli, is given as a synonym; but the Lepas stellata of Poli is a Chthamalus, and this certainly is not the case with B. stellaris. I have received two specimens from the Continent named B. stellaris, but they certainly differed from the form so called by Bronn, for in that, the parietes are said to be porose and the radii very narrow: these foreign specimens I have named B. inclusus. A species described by me as B. corrugatus, resembles in external appearance the B. stellaris of Bronn, but it is mere labour in vain to attempt identifying Balani by their external characters.

B. striatus, Defrance: see remarks under B. circinnatus.

B. tertiarius, Risso, ‘Hist. Nat. de l’Europe Merid.,’ vol. iv. I cannot recognise this species.

B. tesselatus, Sowerby, a synonym of B. porcatus; recent and fossil: see remarks under B. costatus.

B. zonarius, Münster: see remarks under B. ornatus; possibly this is a synonym of B. concavus.

B. amphimorphus, Lamarck: see remarks under B. pustularis.

B. crispatus, var. of B. tintinnabulum.

B. cylindraceus, Lamarck. From Chenu’s ‘Illust. Conch.,’ in which work Lamarck’s original specimens are figured; it appears that this is the B. psittacus of South America, where it is also found fossil, but assuredly Lamarck is quite in error when he states that a variety of this species occurs fossil near Turin. Bronn (in his ‘Italiens Tertiär-Gebilde,’ ) gives as a synonym to the Turin fossil the Lepas tintinnabulum of Brocchi (in the ‘Conchologia Fossile Subapennina,’ t. 2, ), and this probably is correct; and I have hardly any doubt that the Lepas tintinnabulum of Brocchi is the B. concavus of Bronn described in the present work.

B. perforatus of Bruguière is said by Philippi to be found in Sicily: see remarks under B. tulipa.

B. semiplicatus, Lamarck: see remarks under B. pustularis.

B. tulipa of Müller is the B. Hameri of this work, under which name full information on its geological history has been given. The B. tulipa of Poli and Ranzani is the B. tulipiformis of the present work; and this latter species is said by Philippi to occur fossil in Sicily. But there has been so much confusion in the identification of B. tulipiformis, B. Hameri, and B. tintinnabulum, and likewise of B. perforatus (which by Poli was wrongly considered to be L. balanus, Linn.), that doubts must be entertained about which have been really found, until the Sicilian fossils are all carefully examined.

B. ovularis, Lamarck: see remarks under B. pustularis.

B. Uddevallensis, Linnæus, is probably a synonym of the B. Hameri of this work and the B. tulipa of Müller.

[A few other references may be added to those given by Bronn.]

B. miser, stated by Lamarck to be found fossil: see remarks under B. pustularis.

B. patellaris of Lamarck, is stated by Marcel de Serres to be found fossil with several other species of Balanus; thus named without any description in the ‘Annales des Scien. Phys. et Nat. de Lyon,’ tom. i, .

B. virgatus, delphinus, and crispus, are names given by Defrance, with absolutely worthless descriptions.

 

B. radiatus is too briefly described by Risso (‘Hist. Nat. de l’Europe Merid.,’ tom. iv, 1826), without a figure, to be recognised; it probably is not the B. radiatus of Spengler, Wood, and other authors.

B. goissopomo, lævis, and radiatus, are mere names without any description, published in a Catalogue by F. Hoeninghaus, in the ‘Jahrbuch für Mineral. Geog.,’ &c., 1831, .

B. humilis. Conrad, in the ‘American Journal of Science,’ vol. ii (N. S.), , 1846, has given a short description, with a woodcut, of this species, from the upper Eocene of Florida. The opercular valves are not described, and I doubt whether the species could be recognised.

 

2. Family — VERRUCIDÆ.

Cirripedia without a peduncle: scuta and terga, not furnished with depressor muscles, moveable only on one side, on the other side united immoveably with the rostrum and carina into an asymmetrical shell.

The one genus herein contained differs so considerably from all the others in the Order, in the extraordinary unequal development of the two sides of the shell, that I have instituted a Family for its reception. If compelled to place it in one of the foregoing families, I should with much hesitation rank it in the sub-family Chthamalinæ, rather than amongst the Lepadidæ; for it is destitute of a peduncle, and has a shell, though a very different one from that of any true sessile cirripede. In the interfolding sutures which may be considered as representing radii or alæ, in the basis being divided into concentric slips, and in the whole of the basis being attached to the supporting object, this same line of affinity is clearly manifested. On the other hand, in the general shape, manner of growth, and kind of articulation of the scutum and tergum, there is so close an approach to the Lepadidæ, that had I seen these very important valves separately, I should certainly have concluded that they had come from a Pollicipes, allied to certain Cretacean fossil species, as P. fallax and elegans; it likewise, perhaps, deserves notice, that the upward growth of the rostrum, in Verruca nexa, is a peculiarity found only in the valves of the Lepadidæ. Verruca differs both from the Lepadidæ and Balanidæ in the whole shell or external covering, having no other muscle besides the adductor scutorum. In the characters derived from the animal’s body, Verruca approaches both families; but in the absence of branchiæ, and in the great development of the caudal appendages, perhaps it comes rather the nearest to the Lepadidæ. Whatever affinity there is to the Balanidæ, it is much stronger to the sub-family Chthamalinæ than to the Balaninæ; though the non-bullate labrum, in three of the species, and the great dissimilarity of the third cirrus from the three posterior pairs, at first seems to indicate a closer relationship to the Balaninæ; but the labrum is never notched, as in the latter sub-family, and in V. nexa it is bullate, and supports palpi of only small size. The dissimilarity, also, of the third pair of cirri, compared with the posterior pairs, is hardly greater than in Chthamalus intertextus and Chamæsipho columna, members of the Chthamalinæ, though abnormal in this one respect. Perhaps even a special affinity is evinced between certain species of Chthamalus, as C. intertextus, and certain species of Verruca, as V. nexa, namely, in the interfolding sutures and in the very peculiar, inflected basal margin of the walls. Upon the whole, the affinities of the Verrucidæ are complex, and nearly equally divided between the two great families of Balanidæ and Lepadidæ, or sessile and pedunculated cirripedes.

 

Genus — VERRUCA. Pl. 21.

VERRUCA. Schumacher. Essai d’un Nouveau Syst. Class., 1817.

CLYSIA. Leach. Journal de Physique, tom. 85, July, 1817; Clisia, Leach, Encyclop. Brit. Suppl., vol. 3, 1824; Clitia, G. B. Sowerby, Genera of Recent and Fossil Shells.

 

CREUSIA. Lamarck. Animaux sans Vertèbres, 1818.

OCHTHOSIA. Ranzani. Memoire di Storia Nat., 1820.

LEPAS ET BALANUS AUCTORUM.

According to Bock, in the ‘Naturforscher’ of 1778, this term was used by Rumph for a Chelonobia, but as it was before the adoption of the binomial nomenclature, according to the Rules, it may be passed over, and does not interfere with the priority of Schumacher.

Distribution, Northern Europe, Mediterranean, Red Sea, Madeira, West Indies, Tierra del Fuego, Chile, Peru.

The shell in this genus is extremely unsymmetrical, not two of the six pieces of which it is composed quite resembling each other. At first it appeared hopelessly difficult to identify, in a homological sense, these six valves, with those of ordinary cirripedes, but the difficulty soon quite vanished. The operculum consists of two moveable valves on one side, namely, a scutum and tergum, but without any moveable valves on the opposed side: the scutum, though remarkable from being much smaller than the tergum, can be easily recognised by giving attachment to the animal’s body and to the adductor scutorum muscle. The four other pieces are articulated together, and form the shell surrounding the sack, in which the animal’s body is enclosed: of these, the two against which the moveable scutum and tergum shut, are smaller, differ greatly in shape, and are articulated together in a different manner from the remaining two pieces; from these facts alone there would be a strong presumption that they were of a different nature. The fixed valve, against which the scutum shuts, is either furnished with a remarkably prominent plate (a in fig. 1 c, s′; compare this with s′ in the reversed shell in fig. 1 e), or is hollowed out, as in V. nexa, for the attachment of the adductor scutorum muscle. Thus it is rendered probable that this fixed valve is a modified scutum; but a surface of attachment for one end of the adductor muscle might, perhaps, have been developed on any other valve, or a scutum might have become fused with a lateral valve of the shell; the shell on this latter view being rendered in idea more symmetrical. But when a very young specimen is carefully examined, it is found that the moveable and fixed scutum, the moveable tergum and its opposed valve or fixed tergum, at the first period of calcification, resemble each other quite closely; but that, as each zone of shell is added, the differences become rapidly greater and greater: hence, it may be considered as directly proved, that the two fixed valves (S′ and T′ in all the figures in Pl. 21), which are opposed to the moveable valves of the operculum (S and T), consist of an extraordinarily modified scutum and tergum. It has been shown (), that at the period of the metamorphosis, the two scuta, the two terga, and the carina of the Lepadidæ, commence their growth, under the form of the so-called “primordial valves,” and so differ from all the other valves when such occur: now, in two species of Verruca, I have found closely analogous primordial valves on the apices of both the moveable and fixed scutum and tergum (thus affording strong additional evidence that their nature has been rightly interpreted), and on one of the two remaining valves, namely, that at the posterior or carinal end of the shell. Hence, we may safely infer, that this latter valve, which, though very much more developed on one than on the other side, is so far medial as to curl round and cover the line of opening between the moveable and fixed tergum, is really a carina. The sixth valve differs only very slightly in shape from the carina, and is directly opposed to it; therefore, in accordance with all analogy, it must be the rostrum. Consequently, the shell in Verruca consists of a moveable scutum and tergum, a fixed scutum and tergum, a carina and rostrum, and, as we shall immediately see, a membranous basis — the basis being, as in all sessile cirripedes, the homologue of the peduncle in the Lepadidæ.

The moveable scutum and tergum stand at about right angles with the fixed pair; and as these latter form a part of the wall of the shell, which is always steep on this side, the moveable pair, which close the orifice, are nearly horizontal or parallel to the basis and surface of attachment. Hence, the animal’s body, which is attached between the two scuta, but nearest to the moveable scutum, also, lies nearly parallel to the surface of attachment; and I was consequently at first led to suspect that the basal membrane was one side of the shell in a modified condition; but the presence of the prehensile antennæ of the pupa in nearly the middle of this membrane, and the sheet of cement-tissue on its under side, demonstrate that this membrane, though lying on one side of the animal, is the true basis. To make all the parts in Verruca hold the same position as in other cirripedes, relatively to the surface of attachment, we must develope the carina and rostrum equally on both sides of the true longitudinal axis of the shell, and insert the newly-developed portion between the basis and the fixed scutum and tergum, reducing the latter in size, and tilting a little up the moveable scutum and tergum; and by this means the animal’s body would be turned, so that its dorso-ventral longitudinal plane would stand at right angles to the basal membrane.

Extraordinarily great as is the difference between the right and left sides of the whole shell, yet in all the species it seems to be entirely a matter of chance whether it be the right scutum and tergum with the right side of the rostrum and carina, or the left scutum and tergum with the left side of the rostrum and carina, which become abnormally developed. Nor does there seem to be any relation between the side of the operculum to be attached, whether right or left, and the nature of the surface of attachment; for I have seen many specimens adhering to perfectly level surfaces, and to quite cylindrical branches of Laminariæ; and in these cases, however the larva might attach itself, there could be nothing to favour the development of one side more than the other. Although the attached scuta and terga are larger than the moveable pair, yet, owing to the small development of the carina and rostrum on the attached side, the upper or unattached side must be considered as the most developed. In this respect, and in the circumstance of either right or left side being modified, we are reminded of the structure of Pœcilasma Kæmpferi (described in my former volume on the Lepadidæ), in which the valves on the side of the capitulum, nearest to the crab’s body, to which the specimens were attached, were somewhat less developed than those on the opposite side. I may add, that in ordinary Crustaceans, as I am informed by Professor Bell, the unequal development of the thoracic limbs seems quite capriciously to affect either the left or right side of the body.

General Appearance of the Shell. — The shell is in most cases much depressed and irregularly circular; the side formed by the fixed scutum and tergum is always steeper than the other side: the colour is white or pale brownish, and in V. nexa pale red. The surface is naked. The size is small, rarely exceeding a quarter of an inch in diameter, and the whole shell often appears like a mere scale on the surface of attachment. The most remarkable feature in the external aspect is due to the suture between the rostrum and carina, which is formed by oblique, interlocking plates or folds; as all these plates continue to be added to at their extremities during growth, the upper plates become longer than the lower ones; and the plates on both sides of the suture together form a triangular area, with the broad end uppermost, somewhat like the radius of a sessile cirripede: they act, also, like a radius, for their growth serves to separate these two valves, and so adds to the diameter of the shell. The suture between the rostrum and fixed scutum and that between the carina and fixed tergum are nearly of the same nature, but the former is more conspicuous than the latter; neither are so conspicuous as that between the carina and rostrum: accordingly as the right or left scutum and tergum are moveable, so the suture, second in plainness, (see Pl. 21, fig. 1 a, and 1 d,) is placed to the left or right hand. The fourth suture, between the fixed scutum and tergum, as viewed externally, is straight, and so very obscure that it has been overlooked by some authors, and the shell described as consisting of only three nearly equal pieces, for the fixed scutum and tergum together are about equal in size to the carina or rostrum. The orifice approaches more nearly to an unequal-sided triangle, with the apex broadly truncated, than to any other figure. The operculum fits with remarkable closeness, and is surrounded by a slight rim, formed by the edges of the four other valves.

Moveable Scutum and Tergum. — The scutum (S in 1 b and 5) is narrow and very small, barely equalling half the size of the tergum, and therefore proportionally much smaller than in any other cirripede; in a very young shell, however, (of V. Strömia) less than a pin’s head in size, the scutum equalled the tergum in size. The valve is remarkably thick; it is generally depressed down the middle; but in V. nexa this part is longitudinally ribbed. The occludent margin is curved. On the tergal margin there are two articular ridges (with a deepish furrow between them), of which the upper one (′ in S, in fig. 1 b, and 5) extends from the apex about half-way down the valve; and the other, or lower articular ridge (′′ in S), generally runs down nearly to the basal margin: an angle, running from the apex to the basi-tergal corner of the valve, appears like a third articular ridge, but cannot properly be considered such. The above two articular ridges interfold with analogous ones on the scutal margin of the tergum, and so lock the valves together. On the under side (fig. 1 f), the surface is bounded along the occludent margin by a slight rim: there is generally a very slight depression for the adductor muscle; but in V. Spengleri there is a straight, short, sharp (Pl. 21, fig. 2), prominent adductor ridge.

The moveable tergum is broad and rhomboidal. Externally a prominent axial ridge (′′′ in T, in fig. 1 b, &c.), which widens downwards, runs from the apex of the valve to the basal point, and there projecting slightly, causes the scutum to be indented; this indentation on the scutum appears like a third articular ridge, lying beneath (′′), S, in fig. 1 b, &c. Above the lower and axial ridge, on the scutal margin of the tergum, there is a middle articular ridge, which locks in, between the lower (′′) and upper articular ridges (′) of the scutum (S). Again above the middle ridge there is an upper and third articular ridge (′), which is either quite distinct, as in fig. 5, T, or more commonly is formed by the occludent margin of the valve, as in T, fig. 1 b. The broad extremity of this upper articular ridge is often produced into a slight projection, or shoulder, and this always underlies the scutum, of which the under and upper surface is indented or furrowed (see fig. 1 f), in order to receive this shoulder. The upper articular ridge of the scutum (′, S, 1 b) locks in between the upper articular ridge or occludent margin (′, T), and the middle ridge (′′, T) of the tergum.

Hence, altogether, there are three articular ridges on the scutal margin of the tergum, the occludent margin being generally counted as one; whereas, on the tergal margin of the scutum, there are only two ridges, though, as before noticed, an outer indentation, which is developed as a ridge in V. nexa (fig. 5, S), might almost be counted as a third articular ridge.

I may here just remark, that the furrow between the two ridges on the tergal margin of the scutum, resembles the articular furrow in the scutum of the Balanidæ; but it may be doubted whether the resemblance be more than superficial, as this furrow, in the case of Balanidæ, receives the edge itself of the tergum, whereas here it receives only a ridge, proceeding from the apex of the tergum, to a nearly middle point on its scutal margin. Finally, I may add, that the tergum in this genus, in general shape, in growth (presently to be referred to), in the manner in which the upper scutal shoulder is overlapped by the scutum, and in the presence of the axial ridge, presents a very striking resemblance to certain old fossil species of Pollicipes, and to a limited extent to the living species of Lithotrya.

The scutum and tergum being interlocked, move together; they can be firmly shut by the contraction of the long adductor scutorum muscle. Their opening appears partly due to the elasticity of the membranous hinge (representing the opercular membrane), by which they are attached transversely, just beneath the summit of the carina and rostrum. No doubt the protrusion of the cirri effectively aids the act of opening. These valves are not capable (nor, of course, the other valves) of any other movement; for there are no muscles for such movements.

Fixed Scutum and Tergum. — The fixed scutum is larger than the fixed tergum, and therefore has the same proportions as the homologous valves in ordinary cirripedia, but reversed proportions compared with the moveable scutum and tergum. The shape of neither valve can hardly be described. The fixed Scutum (S′ in all the figs.), externally, seems at first to consist of two portions, namely, a curved occludent rim (a), closely resembling the opposed occludent margin (a) of the moveable scutum (S), having in fact undergone very little modification, (as may be best seen in Pl. 21, fig. 1 b); and secondly, of a much modified portion (marked ′′), which resembles in outline and state of surface the rest of the walls of the shell, and may be called the parietal portion. The rostrum (A) curls round the end of the occludent portion, under an edge (b), evidently answering to the basal margin (b) of the moveable scutum, and is simply united to this portion by membrane, but beyond this part, it is articulated to the parietal portion (′′) of the fixed scutum, by oblique interlocking ridges, like those forming the suture between the rostrum and carina. In V. nexa, however, (fig. 5) the rostrum (A) does not curl round any part of the interlocking fixed scutum (S′), but articulates with it by a straight suture. Internally, the fixed scutum (S′ in figs. 1 e, 1 c, of reversed shells) has a surprisingly large, thin adductor plate (m in fig. 1 c, 1 b), with a rounded outline, projecting nearly parallel to the basis or surface of attachment; the adductor scutorum muscle is attached to its upper surface, and consequently the animal’s body lies between this plate and the moveable scutum. In the fixed scutum of V. nexa, however, there is a deep pit, instead of a plate, for this muscle.

The fixed Tergum, likewise, consists of two portions — a middle and lower, or parietal portion, and a rim or upper portion; the rim consists of two unequal arms, answering to the two upper margins (not merely the edges) of the rhomboidal moveable tergum; the longer rim (x in T′, see fig. 5) answers to the carinal margin (x) of the moveable tergum, and may be called the carinal rim; and the shorter rim (o and ′ in fig. 5) answers to the occludent margin (o and ′) of the moveable valve, and may be called the occludent rim. The carina curls round the end of the carinal rim, under an edge, z (much foreshortened in T′ in fig. 1 b, and best seen in fig. 5), answering to at least a large part of the basal margin (z) of the moveable tergum, and interlocks, by a serrated suture, with the edge of the parietal portion of the valve. Internally (fig. 1 e, less plain in 1 c) there is a transverse ledge, notched in the middle, and sometimes deeply hollow beneath, running across the valve in about the line of the adductor plate of the fixed scutum: this ledge, in fact, marks and is partly caused by, the line of separation between the central or parietal, much modified, and the scarcely modified, upper or rim portion of the valve. The use of this ledge is apparently to give attachment, as does the under side of the adductor plate of the fixed scutum, to ligamentous fibres, presently to be mentioned, by which the shell is attached to the basal membrane: the carina and rostrum being so much more gently inclined, do not stand in need of a ledge for their attachment.

By comparing the moveable scutum and tergum with the corresponding fixed valves, in all the species, the modification of the latter may be clearly made out to have been effected as follows; and the case appears to me a striking and interesting one. The moveable scutum and tergum lie in the same plane, and are articulated by the means of three ridges on the tergum (including the occludent margin), and by two on the scutum. The fixed scutum and tergum have to be curved, and to be greatly increased in size; and this is brought about, as we shall see, by the large development of a certain small portion of each valve. Comparing first the moveable tergum (T) with the fixed tergum (T′), the umbo of growth matches the umbo of the four margins of the moveable valve, the carinal (x), basal (z), and occludent (o in fig. 5), margins can be identified with certainty in the fixed valve, from their close similarity in shape, their absolute apposition, or correspondence in position. There remains only the scutal or articular margin, with its three articular ridges; of these, the uppermost (′), inasmuch as in most of the species it is hardly distinct from the occludent margin, can, as we have just seen, be clearly identified, and is overlapped, as it normally should be, by the upper tergal corner of the fixed scutum: the second or middle articular ridge, though not so distinct as in the moveable valves, can be plainly recognised (′′), T′, in fig. 1 b, and 5; and it serves its normal function of articulating the two valves together. But when we look in the fixed valve for the third or axial ridge (′′′), we find in its exact place, namely, extending from the umbo to the extreme opposite end of the valve, between the second articular ridge (′′) and the basal margin (z, see fig. 5), only that portion of the valve which I have called the parietal portion; consequently, I do not doubt that this really is the axial ridge largely expanded. So again in comparing the moveable scutum (S) with the fixed scutum (S′); two of the three margins of the former, namely, the occludent (a, see fig. 1 b) and basal (b), can be identified without a doubt in the fixed valve: the third and tergal margin remains; this should have two articular ridges; of these the upper one, still serving its normal function, can be detected in all the species (′ in fig. 1 b), and can be seen pretty plainly (′ fig. 5) in V. nexa: but of the lower and other articular ridge there is no sign, — excepting indeed the whole parietal portion of the valve, which, from holding an exactly homologous position with the lower articular ridge of the moveable valve, I cannot doubt in this ridge expanded and curiously metamorphosed. Hence, in both fixed scutum and tergum, it is the outermost or lowest of the articular ridges which has been modified and expanded, so as to rest on and be fixed to the surface of attachment. It would appear as if it had resulted from one ridge in each of these valves having been thus used up by expansion (so to express myself), that the suture between the fixed scutum and tergum is more simple than any other suture in the whole shell; and it is owing probably to this straightness, and consequent tendency to weakness, that the valves do not grow along this line, and so do not become separated from each other during growth, as on the three other lines of suture. As it actually is, owing to this suture never being separated, it is even stronger than the others; its edges on the inside (fig. 1 c), I may add, are a little inflected or prominent.

Rostrum and Carina: these valves differ from each other, only in the former (A) being rather the largest, and in being more plainly articulated with the fixed scutum, than is the carina (B) with the fixed tergum. Their umbones stand in their normal places, at the two ends of the orifice leading into the sack, that is, facing the dorso-ventral longitudinal plane of the animal; but they are very unequally developed on the two sides, and hence they rise very obliquely from the surface of attachment. Their summits are nearly square, which is caused by the continued growth on both sides of the oblique plates or ridges, by which they are articulated with the adjoining valves. These plates strikingly resemble, as already stated, the radii in certain species of Chthamalus. Without these articulating plates, the outline of the rostrum and carina would have been triangular, with the apex upwards. In V. nexa, in which the walls of the shell are almost perpendicular, the rostrum (A, fig. 5) is very peculiar and patelliformed, with the umbo sub-central: this results from the development of a border at the upper end of the valve. In this same species, the basal edges of the rostrum, carina, fixed scutum and tergum, are rectangularly inflected, so as to form a ledge round the basis, as in the case of some few species of Chthamalus, — the ledge appearing like part of the real basis. During the growth of the shell, the upper internal ends of the carina and rostrum are either rendered solid, or a ledge is formed on the inside across their summits, hollow beneath, like the sheath of the Balanidæ, to which solid or hollow ledge the basal margins of the moveable scutum and tergum are attached by a rim of membrane, forming a hinge.

Direction of Growth: Minute Structure of Valves. — The shell grows downwards all round its basal margin. As far as the diametric growth of its upper part is concerned, there may be said to be only three valves, for the fixed scutum and tergum never become, as already stated, separated; on the three other lines of suture, the valves are added to on both sides; and thus the whole upper part of the shell, and the orifice, increases in diameter. The moveable scutum and tergum grow along their basal margins, and along the margins by which they are articulated together; but the scutum in this latter respect, less than the tergum. The summits of the moveable scutum and tergum, during continued growth, become either worn away, or they project freely; in this latter case, an internal ledge is added round the upper end of the fixed scutum and tergum, so as to keep the orifice accurately closed. In V. nexa the rostrum, with its sub-central umbo, is anomalous, as already stated, owing to a broad upper internal border growing in a direction almost directly opposed to the basal growth of the moveable opercular valves.

In young specimens, on the apices of both scuta and both terga, and on the carina, but not on the rostrum, primordial valves may be distinguished, resembling the valves, so called, which first appear (, Introduction) after the metamorphosis in, the Lepadidæ. In the Verrucidæ, however, they are calcareous; and the minute transverse cylinders, of which they appear to be composed, stand further apart, causing the surface of the primordial valve to be marked with little separate circles, instead of by hexagons.

The shelly matter of which the valves are composed is translucent: it is remarkably destitute of any investing membrane. The under surface is marked with rows of minute approximate pores, parallel to the lines of growth, into which the corium enters: after a portion of shell has been dissolved in acid, these threads of corium are seen to change, a short distance within, into cylinders of yellow chitine, running obliquely through the substance of the valve. These cylinders are about 1/2000th of an inch in diameter, but in parts they are spindle-shaped and twice as thick: they vary in length, about 1/100th of an inch being the average length: these cylinders at their upper ends suddenly contract into a point, more or less long, or are produced into a very fine tortuous tubulus of chitine, imbedded in the shell: I have seen in no other Cirripedes tubuli of this structure. There are other ordinary tubuli, such as occur in the valves of most Cirripedes, about 1/6000th of an inch in diameter, and which sometimes alternate with the above-described thicker cylinders. There are no external spines. From the number and length of the tubuli of both kinds, the tissue left after the action of acid is singularly complicated.

Basis. — The basal membrane is thin, and is divided, but not very plainly, into concentric slips, marking the successive increments of growth. In the middle of it, in two young specimens, I found with great difficulty the pupal prehensile antennæ: they were of small size, measuring from the extreme edge of the main or second segment to the end of the disc, only 27/6000ths of an inch: the disc appeared narrow (as in Pollicipes and Scalpellum), with a single spine at the proximate end: the ultimate segment, placed as usual at about right angles to the disc, bore two groups of shorter and longer spines, but I could not count how many. The antennæ were enveloped in a mass of cement of a yellow colour, resembling in all its characters the cement of other Cirripedes. In only one case, I believe I saw bifurcating cement-ducts, of extreme tenuity, viz. 1/15,000th of an inch in diameter. The sheet of cement on the whole under side of the basal membrane, not rarely shows a very irregular reticulated structure. For convenience sake, it will be best to defer the discussion on the very anomalous, though slight, powers of excavation which this genus possesses, and which I must attribute to the effects of some substance secreted probably by the cement-organs. I will here only mention, that the specimens which have excavated a depression, are less firmly attached than those, which have not acted on their support; and that, in the former case, the basal membrane, for a considerable space in the middle, becomes quite detached.

Animal’s Body. — The body is much flattened and, owing to the little development of one side of the shell, lies parallel to the surface of attachment. The prosoma is but little protuberant. The articulations of the thorax are unusually straight and transverse. The Mouth is also much flattened: it is placed rather distantly from the adductor scutorum muscle, owing to the production of the lower margin of the labrum. The Labrum is not notched, or even hollowed out in the middle, or (excepting in V. nexa) bullate; its crest is surmounted by about eight (more numerous in V. nexa) little teeth, or by some fine bristles. The Palpi are of moderate size, with their tips nearly meeting; they are slightly curved, and have bristles only on their outer sides and extremities: they are apparently capable of being lifted up and down by a muscle attached to them, just outside the rounded swelling on each side of the labrum to which they are articulated: in V. nexa, however, the palpi are very small and narrow, and their tips do not nearly meet. In this genus, therefore, we find the swollen state of the labrum and the size of the palpi — characters generally invariable and of high classificatory importance — variable. The mandibles have three upper main teeth, with two or three minute lower teeth, or, in V. nexa, with the lower part pectinated with small spines: in V. Strömia, I have seen traces of the second tooth being laterally double — a character of some importance. The Maxillæ have a notch under the upper pair of large spines, with the lower part bearing, as usual, a double row of bristles, and forming a large step-formed projection: these organs are furnished with the usual apodeme and muscles. The Outer Maxillæ are prominent, and deeply lobed on their inner surfaces, the two lobes being clothed with bristles.

Cirri. — The first pair are attached, as usual, on each side of the mouth, and stand some way apart from the five posterior pairs. The second and third pairs differ considerably in structure from the three posterior pairs, which are much elongated. The first pair (excepting in V. nexa) is short, with the two rami slightly unequal in length, and with the segments thickly clothed, as usual, with spines. The second pair is remarkable from the posterior ramus being more than twice as long, and containing thrice as many segments, as the anterior ramus, which is barely as long as the shorter ramus of the first pair: the segments in the anterior ramus of the second pair (only five in number in a full-sized specimen) are broader and more protuberant in front, and more thickly clothed with spines (the terminal spines being doubly pectinated), than are the segments on the posterior ramus; on the latter, the uppermost segments have their bristles arranged in front in simple pairs, with the dorsal spines long, the lower segments being more thickly clothed with bristles, owing to the development of lateral rows. The third pair resembles in every respect the second pair, except in being a little longer, and in the bristles on the posterior ramus being less crowded, more resembling the arrangement of those on the posterior cirri. In V. nexa, however, there is not so great an inequality in length or dissimilarity in structure in the two rami of the second cirrus, and only a very slight difference of any kind in the two rami of the third pair. Fourth, fifth, and sixth pairs have numerous elongated segments, bearing four or three pairs of long slender spines in front, with a single minute bristle between each pair, and with two or three slender spines in the dorsal tuft.

There is a considerable amount of variation in the proportional length, and in the number of the segments, of the several cirri in V. Strömia; in some specimens the two rami of the fourth pair were unequal in length; in some, nearly all the cirri on the lower or attached side were shorter than those on the upper side.

 

Caudal Appendages. — These are of most unusual length, sometimes even exceeding those of Ibla quadrivalvis, which surpasses, in this respect, all other cirripedes. They arise on each side and over the anus. They consist of numerous (sometimes as many as twenty-four), unequal, cylindrical, thin segments, bearing, at their upper ends, a circle of long and very slender spines. They sometimes equal two thirds or even four fifths of the length of the sixth cirrus; but their length, and the number of their segments, (sometimes imperfectly divided), varies much in different specimens of the same species, and sometimes even on opposite sides of the same individual. In some very young shells, as big as a pin’s head, the caudal appendages were proportionally extremely short, and consisted of only two or three segments. No muscles enter these organs; and when the animal is taken out of its sack, they project straight out behind, instead of being curled in, like the cirri.

Anatomical Structure. — The animal’s body is attached to the two scuta by the adductor scutorum, and by the other usual muscles running towards the mouth, and surrounding the prosoma. The whole external covering or shell has no other muscles; Verruca thus differing from the Balanidæ and Lepadidæ; but the shell is attached all round, near its circumference, to the basal membrane, by a band of very short fibres, appearing like muscles, but really ligamentous, as determined for me by Professor Quekett. Branchiæ are entirely absent. The alimentary canal presents all the usual characters, but in the prosoma is rather abruptly bent back on itself. The orifices of the two olfactory pouches are not at all prominent; they are placed directly under the outer maxillæ, (homologically in their middle segment), just above a small, medial, tongue-like apodeme. The orifices of the acoustic sacks appeared to be in their usual position beneath the basal articulations of the first pair of cirri. The vesiculæ seminales occupy their usual position in the prosoma; they are not much convoluted; they unite before entering the penis. The probosciformed penis is imperfectly ringed; it is thick and short, and tapers much more abruptly than is usual; it supports a few very thin hairs. The ovarian cæca are spread over the basal membrane, at the bottom of the sack; hence they in fact lie almost on one side of the animal: they consist of two main trunks, proceeding out of the animal’s body at the rostral end of the sack, which then branch and inosculate. In specimens of V. Strömia collected by Mr. Peach for me, in Cornwall, during the first week of April, there were included two ovigerous lamellæ, placed transversely across the rostral and the carinal end of the sack: the lamellæ were .11 of an inch in length; they appeared loose and not attached, as in the Lepadidæ, to any ovigerous fræna. The ova, in their earliest age, have one end much pointed, and are 8/1000ths of an inch in length; they become blunter and increase a little in size before the larvæ burst forth. The larvæ, both during their earliest stage and after the first moult, have been excellently figured and described by Mr. C. Spence Bate: they present no particular characters distinct from the larvæ of other Cirripedes. I will only further add, that the structure of the prehensile antennæ still adherent to the basal membrane, indicates that the larva in its last stage, — that is the locomotive pupa, — has a normal character.

‘Annals and Mag. of Nat. Hist.,’ 1851, Pl. 7, fig. 8-10.

Affinities. — These have been sufficiently discussed under the family; I need here only remark that all the species, with the exception of V. nexa, are intimately allied together.

Range — Habits — Geological History. — The genus Verruca ranges, being represented by four species, from Iceland to Cape Horn. The species that is found in Tierra del Fuego extends up the west coast to Peru. Our northern form, V. Strömia, (if I may trust a specimen in the British Museum, apparently ticketed in an authentic manner), occurs also in the Red Sea; and this is the only locality in the eastern hemisphere whence I have seen this genus. The species seem generally to live in rather deep water: I procured V. lævigata from nineteen fathoms, on the east coast of Patagonia: V. Strömia is found, according to information given me by Professor Forbes, on the British shores, between five and fifty fathoms, and on the steep shore off Mull, in ninety fathoms; but Mr. Thompson assures me that he once saw it adhering to tidal rocks and likewise to some floating bark. Generally the species are attached to living organic bodies, especially shells of Mollusca and of Cirripedes, to Gorgoniæ, and Laminariæ; less frequently to rocks. We shall immediately see that it has slight powers of excavation. This genus is geologically older than any true sessile cirripede or member of the Balanidæ: V. Strömia is found in the Glacial Deposits and in the Red and Coralline Crag of England: another species (in a state not to be identified) occurs in the ancient Tertiary formations of Patagonia; and another in the Chalk of England and Belgium. The fact of this Family ascending to a Secondary epoch accords, in an interesting manner, with its affinities; inasmuch as though in appearance a sessile cirripede, it is almost equally related to the Lepadidæ and Balanidæ, and is more nearly related to the Lepadidæ than to the Balaninæ, or typical members of the Balanidæ: of the latter, none have hitherto been found in any Secondary deposit, whereas the Lepadidæ culminated during the Cretacean period.

Powers of Excavation.

My attention was called to this subject by Mr. Hancock, whose excellent researches on the boring of Mollusca are well known. Verruca Strömia, when attached to shells destitute of an epidermis, excavates, as he informed me, a slight depression, deepest in the middle; but when the epidermis is present no effect whatever is produced. We shall presently see that the central depression is in some degree distinct from that of the circumference. I have since found Mr. Hancock’s observations strictly applicable to V. lævigata, V. Spengleri, and to an ancient tertiary species from Patagonia. From having found that the following cirripedes, viz., Lithotrya, Alcippe, and Cryptophialus, all form their deep excavations by mechanical means, and from having read the above-mentioned memoirs by Mr. Hancock on the boring of mollusca, I was strongly impressed with the idea that the action in Verruca would likewise prove mechanical: but from the following facts I have come to the conclusion that the excavation must be due to a solvent, probably poured out from the cement-ducts, which debouch on the under side of the basal membrane.

In the first place, an epidermis, as just stated, perfectly preserves the shells of the various species of mollusca and certain cirripedes, to which I have seen Verruca attached: this is well shown by comparing the effect produced on the same shell in parts covered by the epidermis and in parts whence it has been abraded; or where the shell of the Verruca had fixed itself, whilst very young, within a crack in the epidermis, and had subsequently, by its growth, turned up the edges, and had then acted on the underlying shell; whereas the specimens attached to the sound epidermis had not produced the smallest effect. Again, I have seen an epidermis-covered mussel-shell encrusted by a hard nullipora, on which V. lævigata was attached; and here the calcareous nullipora, under the middle of the basal membrane, was entirely corroded away, whilst the underlying epidermis and the shell beneath it, were not in the least affected. The protection afforded by the epidermis is still more strikingly shown by contrasting shells with very sharp prominent ridges, when thus invested and when naked, to which Verrucæ have been attached: I have given a figure (Pl. 21, fig. 6) of a piece of an invested Venus, from the surface of which a V. Spengleri had been just removed; on the other hand, I have seen a Peruvian Discina in which even sharper ridges, covered by epidermis, were left absolutely untouched, although projecting deeply into the shell of an attached V. lævigata. I have seen several specimens of this latter Verruca (which has the power of corroding naked shell as deeply as its congeners), attached to the membrane-covered variety of Balanus lævis, the shell of which was thus perfectly preserved: now this membrane is little more than the 1/2000th of an inch in thickness; it is not hard, and so brittle that it generally separates with the Verruca, leaving the underlying shell of the B. lævis with its lines of growth glossy and perfect: it appears to me impossible that a membrane so thin and brittle could resist an action, if mechanical, which has worn away from twenty to forty times as great a thickness of hard shell; but the thinnest film of any matter on which acid does not act, as of grease in certain forms of printing, will perfectly preserve the underlying substance, and as I have ascertained by putting on a drop of acid, is the case with this membrane. I have removed several scores of shells of V. Strömia from the stems of Laminariæ, and when the latter were washed and slightly dried, generally not the least effect could be seen, except that the spots where the shell had adhered were glossy from the still adherent basal membrane: yet the stems of Laminariæ are far from hard. In some cases, however, the attachment of the Verruca seemed to have produced a very slight depression on the Laminaria, but this, I think, may be safely attributed to the growth of the surrounding surface; for I have seen exactly the same effect produced by the attachment of the discs of the antennæ of a Lepas, and these discs, with their long spines, could not possibly produce any excavation; nor is Lepas or its pupa in any case a burrowing animal. Again, I have seen a few specimens of Verruca attached to Gorgoniæ, and they had not acted in the least on the horny axis. I have examined numerous specimens of V. Strömia attached to three pieces of slate-rock, and to one piece of red sandstone, all from different localities, and no effect whatever had been produced; yet the slate-rock, especially in one instance, was soft. Mr. Bate, to whom I am indebted for some of these specimens, also informs me that he could discover no impressions on the slate-rocks, whence specimens of the Verruca had been removed. On the other hand, I have had two specimens of limestone, with attached Verrucæ, one coarse and very impure, and the other hard and marble-like; and in both cases there was a distinct central slight cavity, including loose gritty matter. The loose particles evidently resulted from the unequal action either of a solvent or of some mechanical power on the rock, for it is improbable in the highest degree that the shells should have fixed themselves exactly over small collections of loose particles, even if such could possibly have remained on projecting surfaces of sea-washed rocks.

The above facts seem to indicate pretty plainly that the excavation of the support does not depend on its hardness, but on its containing calcareous matter, liable to be acted on by some solvent: but as this view, considering what we know of Lithotrya and of the two other burrowing genera of cirripedes to be hereafter described, appears improbable, I will add a few additional observations. I most carefully examined the shell and basal membrane of Verruca, and likewise the tissues left after the dissolution of the shell in acid, and could detect no structure at all fitted for boring; and what appears more important, there was no apparent difference in the state of the specimens which had and had not excavated a hollow; and this, I think, would certainly have been the case (as in Lithotrya) if the action had been mechanical. It is not easy to ascertain, owing to the small effect at any time produced, at how early an age Verruca begins to act on its support; but I found two sets of specimens only 1/20th of an inch in basal diameter, which had certainly commenced. The ribbed shell, (Pl. 21, fig. 6), especially the middle rib, shows, in a somewhat exaggerated degree, the typical form of the excavation; it may be here seen that the excavation is of the same depth for some little distance from the circumference towards the centre, but that in the middle it suddenly becomes deeper. I have seen several specimens with a central hollow, without any, or with scarcely any, marginal depression, and likewise the reversed case. These several facts show that the central excavation cannot be due to an equable action, prolonged during the whole growth of the shell, having thus affected the middle more than the circumferential parts, for in this case the excavations would have sloped into each other. In specimens which have not at all acted on their support, the whole basal membrane is firmly attached, as in all ordinary cirripedes, to the supporting surface; but in those which have acted, the middle portion of the basal membrane is quite unattached, and the circumferential portion is, I think, less firmly attached than is usual; but between these two portions, there is a circular zone strongly cemented to the supporting surface, and which alone keeps the shell in its place. Now, on the mechanical theory, to account for the circumferential hollow, the basal edges of the shell together with the circumference of the basal membrane must be subjected to movement, but the shell is united to the basal membrane by corium and by transparent structureless chitine (both of which may be left out of question) and by a circle of short fibres, which adhere at their lower ends to the firmly cemented circular zone, and by their upper ends to the shell; and these fibres have been very carefully examined by Professor Quekett, and pronounced to be not muscular, but exclusively ligamentous, and therefore incapable of moving the edge of the shell. The basal membrane over the central hollow is, as stated, quite loose: its lower surface, formed by a reticulated layer of horny cement-tissue, shows no signs of abrasion, and the membrane is so brittle and tender, that in specimens which have been once dried and then well soaked, it almost invariably cracks when the shell is removed, owing to its mere adhesion to the delicate inner tunics of the sack; yet on the mechanical theory, the wearing of the central hollow must have been caused by the action of this middle portion of the basal membrane, which, it may be repeated, is destitute of muscles. From the presence of the prehensile pupal antennæ, enveloped in cement, nearly in the centre of the basal membrane, it is certain that this spot was originally attached to the supporting surface, and has since been detached from it; as, moreover, the central hollow goes on increasing in diameter with the growth of the shell, it is certain that the inner edge of the firmly attached circular zone of basal membrane must likewise continually go on becoming detached: it may, then, be asked by what force can the basal membrane, seeing that it is united to its own shell above only by fibres of ligament near the circumference, be continually torn away from the underlying support, to which it is strongly cemented? On the other hand, on the theory of a solvent slowly poured out from the cement-ducts, its separation from its support is simply explained. It might be supposed that the calcareous matter, when dissolved, would not be able to escape from the central hollow, owing to the basal membrane being so firmly cemented all round it; but the attachment is by a reticulated layer of cement; and I infer that it must be permeated by open passages, from the fact of the hollow being often filled, in dried specimens, by a bubble of air, instead of the basal membrane being pressed closely down into the hollow, as would have been the case had the hollow been hermetically sealed up. I have seen a few instances in which the bottom of the central hollow was occupied, (as was remarked to me by Mr. Hancock), by a little chalky and gritty matter; and in the case of one of the specimens of calcareous rock, before alluded to, by coarse grains and oxide of iron; this seems quite compatible with a solvent acting more readily on certain parts of the rock or shell than on other and less soluble parts or particles.

Mr. Hancock suggests to me that the basal membrane, on the mechanical theory, need not itself move; the motion of epithelial scales, were they transferred into cutting agents, might be supposed to be sufficient. But of such scales, though I used very high powers, I could see no trace; and their presence on the under side of the layer of cement seems hardly possible. Moreover, according to Von Siebold (‘Anatomie Comparée,’ tom. 1, ), ciliary action has not been observed in any Crustacean, or indeed any Articulate animal. This same statement is likewise made in Annals and Mag. of Nat. Hist. 1854, , by Dr. T. Williams.

The greatest depth of the central hollow, in any specimen seen by me, even measuring from the top of a rib in the case of a ribbed shell, to the deepest point, was only 1/50th of an inch; but considering how much depressed the shell of Verruca is, I have no doubt that this small gain of space is of service to the animal: we must suppose the loose middle portion of the basal membrane is stretched slightly, or splits and is repaired, so as to fit the hollow. With respect to the even much slighter circumferential excavation, it barely equals in depth the thickness of the extreme edges of the walls; it must, I presume, give strength to the shell when laterally pushed; but it certainly appeared to me that the individuals which had excavated a depression for themselves, could be pried vertically up much more easily than those which had not acted on their support. Finally, we must suppose that the hypothetical solvent is poured out of the cement-ducts at the extreme circumference of the basal membrane, which is almost loose and destitute of cement, so as to slightly corrode outwards and downwards the calcareous support; the action here then stops, and this rim of basal membrane becomes, after a new rim has been formed and as the shell grows outwards, firmly cemented down to the now slightly excavated surface of attachment; but during all the time the solvent goes on acting in the middle, and continues, during the whole growth of the shell, to encroach on and dissolve the supporting surface from under the inner edges of the previously cemented down, circular zone of basal membrane. I have discussed this subject at considerable length, as it appears to me an interesting one. In this case we have the action of ciliæ and of respiratory currents, to which in the case of Mollusca so much has been attributed, entirely eliminated. It is, also, an interesting fact, that within the same Order we should have some Cirripedes boring by simply mechanical means, and others by a chemical solvent.

See the previous note to .

The solvent may be carbonic acid gas, as suggested by Mr. C. S. Bate in the case of Mollusca (‘Report of British Association,’ 1849, ), but here, under the basal membrane, we cannot have the respiratory currents, or the ciliary action (see note, supra), as likewise suggested by Mr. Bate.

1. VERRUCA STRÖMIA. Pl. 21, fig. 1 a-1 f.

LEPAS STRÖMIA. O. Müller. Zoolog. Dan. Prod., No. 3025, 1776.

  ——  —   —— Ib. Zoolog. Dan., vol. 3, Tab. 94, 1789.

  —— STRIATA. Pennant. British Zoology, vol. 4, Tab. 38, fig. 7, 1777.

DIE WARZENFORMIGE MEEREICHEL. Spengler. Schriften der Berlin. Gesell., 1 B., Tab. 5, fig. 1-3, 1780.

LEPAS VERRUCA. Spengler. Skrifter af Naturhist. Selskabet, 1 B., 1790.

  ——  —   —— ET STRÖMIA. Gmelin. Syst. Nat., 1789.

BALANUS VERRUCA. Bruguière. Encyclop. Meth., 1789; Clisia verrucosa, Deshayes, in Tab.

  ——  — INTERTEXTUS. Pulteney. Catalogue of Shells of Dorsetshire, 1799.

LEPAS STRIATUS. Montagu. Test. Brit., 1803.

  —— VERRUCA. Wood’s General Conchology, Pl. 9, fig. 5, 1815.

VERRUCA STRÖMII. Schumacher. Essai d’un Nouveau Syst. Class., 1817.

CREUSIA STRÖMIA ET VERRUCA. Lamarck. Animaux sans Vertèbres, 1818.

 

OCHTHOSIA STROEMIA. Ranzani. Memoire di Storia Nat., 1820.

CLISIA STRIATA. Leach. Encyclop. Brit. Suppl., vol. 3 (sine descript.), 1824.

CLITIA VERRUCA. G. B. Sowerby. Genera of Recent and Fossil Shells, Plate.

VERRUCA STRÖMII. J. E. Gray. Annals of Philosophy (new series), vol. 10, Aug., 1825.

Moveable scutum, with the lower articular ridge not half as broad as the short upper articular ridge: shell generally ribbed longitudinally.

Var., with the shell not longitudinally ribbed.

Hab. — Shores of Great Britain and Ireland, Shetland Islands; and, according to various authors, Denmark, Iceland, and shores of northern Europe. Red Sea, Brit. Mus. Attached to shells, laminariæ, rocks, crabs, and floating bark, from low tidal mark to fifty or ninety fathoms.

Fossil in Glacial deposits of Scotland, Mus. Lyell; Red Crag (Walton, Essex), Coralline Crag (Sutton), Mus. S. V. Wood.

I have given so full a description of the genus that little remains to be said under the species. Generally the whole shell is covered (independently of the interfolding, oblique, articulating plates) by narrow, longitudinal ridges or folds; and by this character alone the ordinary variety of V. Strömia can be distinguished (as far as I have seen) from all the other species. The shell is white or dirty yellowish-brown. The scutum has the lower articular ridge on its tergal margin very narrow (but somewhat variable in width), appearing like a mere slight shoulder, against which the longitudinal axial ridge of the tergum abuts: it is not half as wide as the short, upper articular ridge. On the under side there is a very slight depression for the adductor scutorum muscle. There is considerable variation in the degree to which the transverse ledge on the under side of the fixed tergum projects, and therefore in the depth of the hollow thus formed. The specimens with the right-side, and those with the left-side opercular valves moveable, are apparently about equally numerous.

The specimen in the British Museum, from the Red Sea, was attached to a Gorgonia, and was in the same box with a Pyrgoma — circumstances favouring the correctness of the locality — but I am much surprised from the general distribution of the species, that V. Strömia should occur in so distant and isolated an area. After careful examination, I can discover no constant difference between the Red Sea and British specimens.

The specimens from the Crag have not their moveable opercular valves, which offer much more important diagnostic characters than the shell; but as far as the latter is concerned, no difference whatever can be perceived from V. Strömia.

 

2. VERRUCA LÆVIGATA. Pl. 21, fig. 3 a, 3 b.

VERRUCA LÆVIGATA. G. B. Sowerby. Genera of Recent and Fossil Shells, Plate.

Moveable scutum, with the lower articular ridge broader than the short upper articular ridge; moveable tergum broader than high, with the upper articular ridge produced into a point.

Hab. — Tierra del Fuego; Eastern Patagonia, nineteen fathoms; Chile; Peru; Mus. Brit., Cuming, Stutchbury, Darwin: attached to shells, and often to Balanus lævis and psittacus.

I can point out no difference in the shell between this species and V. Strömia, excepting that its walls seem invariably to be smooth, which is rarely the case with V. Strömia; perhaps also the oblique interfolding articular plates between the several compartments are here more prominent. It appears that specimens with the left side uppermost, and therefore with the left opercular valves moveable, are considerably more common than those with the right valves moveable. The moveable scutum and tergum are articulated together by much more prominent articular ridges than in V. Strömia, and the two valves together are broader in proportion to their height, — the height being measured from the apex to the basal margin. In the scutum the lower articular ridge is considerably broader than the short upper ridge. In the tergum, the basi-carinal corner is more rectangular, and the whole valve is nearly square: owing to the deep furrow receiving the lower articular ridge of the scutum, the axial ridge of the tergum is proportionally narrower but more prominent than in V. Strömia; the uppermost ridge (formed by the occludent margin of the valve) projects, especially when viewed on the under side (fig. 3 b), as a moderately sharp point.

In the mouth, the lower teeth of the mandibles are more distinct than in V. Strömia; the lower part of the edge of the maxilla is very prominent. In the second and third pairs of cirri the terminal spines on the shorter rami are coarsely pectinated; on the sixth pair there are only three pairs of main spines on each segment; but these several points, according to the analogy of other species, I should expect to be variable.

This species is alluded to by Bruguière, in the ‘Encyclopédie Méthodique,’ but was confounded by him with the V. Strömia of Europe.

 

3. VERRUCA SPENGLERI. Pl. 21, fig. 2.

Moveable scutum, with a sharp, straight, medial adductor ridge: fixed scutum not larger than the fixed tergum.

Hab. — Madeira, Mus. Lowe; attached to shells.

It would appear that the present species does not attain quite so large a size as the more northern V. Strömia; the walls are not longitudinally ribbed as is usual with this latter species. The proportional sizes of the compartments seem to be somewhat different; the fixed scutum is either equal to or even smaller than the fixed tergum, instead of being larger, as in V. Strömia; but in young individuals the proportions are reversed. In several specimens the fixed scutum and tergum together were larger than the carina. The rounded adductor plate of the fixed scutum is extremely large. The lines of growth, especially on the moveable opercular valves, are rather more plainly crenated than in V. Strömia. In the moveable scutum the lower articular ridge on the tergal margin varies a little in size, and is sometimes larger than in V. Strömia (but never so large as in V. lævigata), and is placed more in the middle of the tergal margin: but by far the most important character by which this species can be distinguished from all the others, is the presence, on the under side of the moveable scutum, of a straight, prominent adductor ridge, which runs up to and even under the apex of the valve, for it is there slightly hollowed out. In the moveable tergum, owing to the medial position of the lower articular ridge of the scutum, the middle of the scutal margin is more hollowed out, and the axial ridge narrower, than in V. Strömia.

In the animal’s body the only difference which I could perceive was that the shorter rami of the second and third pairs of cirri were not so short, compared either to the other cirri or to the longer rami of these same cirri. In the second cirrus, in a moderately-sized specimen, the segments were six and thirteen in number in the two rami, and in the third cirrus, seven and fifteen.

Had it not been for the specimen in the British Museum of V. Strömia, from the Red Sea, I should have concluded, from geographical considerations, that V. Spengleri probably was the species found in the Mediterranean, and noticed by Spengler (‘Schriften der Berl. Gesell.,’ 1 B., 1780), as a small variety of the northern V. Strömia; and likewise that it was the Creusia echinoides of Risso (‘Hist. Nat. Product. de l’Europe,’ tom. 4, , 1826), which is certainly a Verruca, but not described with sufficient minuteness to be recognised.

 

4. VERRUCA NEXA. Pl. 21, fig. 5.

Shell reddish: moveable scutum, with three strongly prominent longitudinal ridges, besides the articular ridges: fixed scutum larger than the carina, with no distinct adductor plate.

Hab. — West Indies, Mus. Brit.; attached to a Gorgonia.

This species differs considerably from all the others in the genus. The shell is brownish-red, tinted yellow: it is not at all depressed like the former species, but the walls are almost perpendicular or even overhang their bases, and the summit of the shell consequently is broad. This form may be in part, but only in part, due to the attachment on the thin branches of the Gorgonia. The umbones of the compartments are remarkably prominent and sharp. Although the parietes are nearly smooth, yet from being so steep, they are little seen, and owing to the very prominent but rounded ribs by which the compartments and opercular valves are articulated together, the whole shell has a strongly ribbed appearance. The diameter of the largest specimen was .2 of an inch.

The rostrum (A, fig. 5) is patelliformed, with the umbo of growth sub-central, but rather above the middle point; hence this valve, differently from the carina, and differently from the rostrum of the other species, grows not only at its basal margin, and on both sides where opposed to the carina and fixed scutum, but also along its upper margin where opposed to the basal edges of the moveable scutum and tergum: owing to the perpendicularity of this valve, the upper part forms a ledge almost parallel to the orifice of the shell. The carina (B) is of unusually small size, being about only half the size of the rostrum, and scarcely exceeding in size the fixed tergum. The fixed scutum (S′) is large, larger even than the carina; it is oblong, and its shape is more simple than in the other species; this is chiefly owing to the rostrum articulating with the whole of that margin (b) which answers to the basal margin of the moveable valve; whereas in the other species (fig. 1 b) it curls beyond this margin, and articulates with the very protuberant, so-called, parietal portion of the valve. Three or four rounded prominent longitudinal ribs, exactly like the homologous ribs on the moveable scutum, run from the apex of the fixed scutum to the basal margin, and their extremities form the teeth by which it articulates, as just stated, with the rostrum. Its upper articular ridge (′) is more prominent, and placed much lower down in the suture between it and the fixed tergum, than in the foregoing species. The ledge (o) by which the orifice is kept neatly closed, is here more distinct than in V. Strömia: this ledge is necessary, as well as in the case of the fixed tergum, owing to the altered shape of the summits of the moveable scutum and tergum, due to their corrosion and to their coming to project freely. But the most remarkable character of the fixed scutum is, that on the under side there is no great adductor plate, but a rounded hollow with its lower edge only slightly prominent; the absence of the adductor plate, which is present in all the other species of the genus, is no doubt due to the under side of this valve being inclined even outwards, and so standing in some degree opposed to the moveable valve; thus affording on its under surface a place for the attachment of the lower end of the adductor scutorum muscle; whereas in the other species this muscle could not possibly have been attached, without the aid of an adductor plate, to the under side of the much depressed and sloping fixed valve. The fixed tergum (T′) is a little more simple in form than the corresponding valve in the other species; the two arms, answering to the occludent and carinal margins of the moveable tergum, are more nearly equal in length: the internal transverse ledge, separating these rims or margins from the parietal portion of the valve, is but little developed.

All four valves forming the shell are remarkable from having, when full-grown, but not whilst young, their basal edges abruptly inflected inwards, thus forming a ledge all round the basal membrane, as in Chthamalus intertextus and Hembeli.

Moveable Scutum. — This is slightly larger in proportion to the tergum than in the foregoing species: it is chiefly remarkable from the presence of three prominent longitudinal ridges on the main part of the valve, like the two articular ridges on the tergal margin; of these latter, the lower one extends down to about the middle of the tergal margin. The moveable tergum is rhomboidal, with the whole carinal portion marked only by lines of growth: it is only remarkable by the upper of the three articular ridges on the scutal margin being unusually distinct from the occludent margin.

With respect to the animal’s body, its several peculiarities have already been pointed out under the genus. The labrum is decidedly bullate, triangular in section, with a row of minute bead-like teeth on the crest; the palpi are very narrow and short, and do not nearly touch each other: this variation in the structure of the labrum and in the size of the palpi, is very remarkable, considering how important, in a classificatory point of view, these parts are in all other Cirripedes. In the mandibles there are either two or three main teeth, with the whole lower part of the organ pectinated with sharp spines. Cirri: the first pair is not short; in the individual examined, the two rami had eleven and twelve segments. In the second pair, the shorter ramus was two thirds of the length of the longer ramus, the segments being in number ten and fifteen; in the arrangement of the spines this second pair resembles its homologue in the three other species. In the third pair, the two rami are very nearly equal in length, having sixteen and eighteen segments; and the segments of the anterior ramus are only a little thicker and more thickly clothed with spines than those of the posterior ramus. The remaining cirri and the caudal appendages are as in the other species.

 

5. VERRUCA PRISCA. Pl. 21, fig. 4.

VERRUCA PRISCA. Bosquet. Monographie des Crustacés fossiles du Terrain Crét. de Limbourg, Tab. 1, fig. 1-6; 1853.

Shell smooth: moveable scutum, with the lower articular ridge somewhat broader than the upper articular ridge.

Fossil— ‘Système Senonien et Maestrichtien,’ Belgium, Mus. Bosquet; in Chalk, Norwich, Mus. J. de C. Sowerby.

M. Bosquet has admirably figured and described the several separated valves belonging to this species, and I owe to his great kindness an examination of some of them. In Mr. J. de C. Sowerby’s collection, also, there is a single specimen, attached to a Mollusc, with the four valves of the shell united together, but without the two moveable opercular valves; it cannot be positively asserted that this is the same species with that of M. Bosquet, but such probably is the case. This is the species to which I alluded in the Introduction to my ‘Monograph on Fossil Lepadidæ.’ It is an interesting species, from being the only known Secondary one, but in itself it is a very poorly characterised form, and I can point out no important character in the shell by which it can be recognised. The rostrum and carina, which are of nearly equal sizes, are locked together by the usual interfolding plates, and likewise to the fixed scutum and tergum; but these latter plates seem to have been less developed in M. Bosquet’s specimen than in the English. The fixed scutum has a large adductor plate, which seems to have been chipped in M. Bosquet’s specimen; this valve and the fixed tergum in all essential respects resemble the same valves in V. Strömia. The surface of the shell is very smooth.

The moveable scutum has its occludent margin considerably arched: the lower articular ridge is broader than the upper ridge, in which respects it resembles the same valve in V. lævigata, but the whole valve is not so broad as in that species. There is no adductor ridge on the under surface. The moveable tergum has its upper articular ridge narrow, and slightly produced into a point on the scutal margin: in this latter respect this species also resembles V. lævigata, but the whole valve is not so broad in proportion to its height.

 

3. Family LEPADIDÆ.

Cirripedia having a flexible peduncle, provided with muscles: scuta and terga, when present, not furnished with depressor muscles: other valves, when present, not united into an immoveable ring.

This Family has been fully treated of in my former volume, published by the Ray Society, and I should here only have alluded to its existence, had it not been for the genus Alcippe, which differs in so many important characters from the other members of the Lepadidæ, that formerly I did not even suspect that it could belong to this Family, and therefore deferred its examination. The genus Alcippe was discovered, well described and illustrated, in 1849, by Mr. Hancock; to whose very great kindness I am indebted for permission to dissect and examine his entire stock of this truly remarkable Cirripede. In the classification of the whole class I have not felt so much doubt, as whether I ought to institute a family for the reception of this genus. Alcippe differs from all other Cirripedes (putting on one side for the instant, the males and complemental males of Ibla and Scalpellum) in the very singular fact of being destitute of a rectum and anus; — in the three segments of the thorax, which usually support the second, third, and fourth pairs of cirri, being without any appendages; — in the fifth and sixth pairs of cirri having their inner or posterior rami metamorphosed into very singular roughened cushions or buttons, which apparently serve to triturate the food; — in the caudal appendages being muscular, and being used conjointly with the cirri; — and lastly, in the pupa having a lesser number of segments in its abdomen and caudal appendages than in (as far as I have seen) any other Cirripede. It will be thought that these characters are amply sufficient to justify the placing Alcippe in a separate family, more especially when the close general resemblance in the animal’s body in most of the other members of the Balanidæ, Verrucidæ, and Lepadidæ, is borne in mind. On the other hand, the males and complemental males of Scalpellum and Ibla must indisputably be considered as members of the Lepadidæ; yet the male of Scalpellum vulgare and ornatum has no stomach, anus, or mouth, which is a far more abnormal structure than the absence only of the anus in Alcippe: the cirri, also, in these same males, differ from the ordinary cirripedial type decidedly more than in Alcippe. Again, in the male of Ibla, all the cirri, excepting the fifth and sixth pairs, are aborted, and these two pairs are usually only uniramous; here, then, we have a decided resemblance to Alcippe. Hence, if we might assume that the female Alcippe had partially assumed characters confined to the males of the other genera, it would assuredly stand amongst the Lepadidæ. Independently of this comparison with the foregoing males, the affinities of Alcippe are so special to several genera amongst the Lepadidæ, that it seems unnatural to force it out of the position which it well occupies between Ibla and Anelasma, and place it in another family by itself: thus, in being bisexual, and in the general character of its very curious males, Alcippe shows an affinity to Ibla and Scalpellum; and to the former of these genera it is related in several particulars, such as in the body being lodged within the peduncle, and in the structure of the larval antennæ, &c.: to Anelasma and Alepas it is allied in the general character, and to a certain extent in the muscles, of the capitulum; Anelasma, also, has all its cirri to a certain degree rudimentary, and Alepas cornuta has the inner rami of the fifth and sixth pairs of cirri, — namely, the very same rami which are so curiously modified in Alcippe, — small, destitute of muscles, and functionless for their proper purpose: to Anelasma and Lithotrya it is allied in the peculiarity of the lower end of the peduncle becoming elongated by growth, and in being imbedded; and to Lithotrya by its powers of excavation and manner of attachment. Now, I believe it generally holds good that when a form is really distinct from another group, its affinities are general, or only in a slight degree special to the members of that group. Nor, indeed, can it be asserted that Alcippe differs much more, somewhat more it certainly does, from the other genera, than does Anelasma, with its more singular mouth, spineless rudimentary cirri, and fimbriated peduncle; and I have never regretted having included this genus amongst the Lepadidæ. Hence, after much consideration, I have resolved to consider Alcippe as one of the Lepadidæ, though so curiously modified, and having characters confined to the males of the other genera. Perhaps I have been in some degree influenced by the difficulty of finding external characters by which to separate Alcippe as a family from the other Lepadidæ.

The fossil species have been described in a separate Monograph published by the Palæontographical Society. Since its publication, M. Bosquet has produced an excellent memoir, containing descriptions, with the most beautiful illustrations, of several new Cretacean species of Pollicipes and Scalpellum. The memoir is entitled a ‘Monographie des Crustacés Fossiles du Terrain Crétacé, du D. de Limbourg.’

Adrien de Jussieu, in his ‘Memoir on the Malpighiaceæ,’ ‘Archives du Museum,’ tom. 3, , when speaking of the characters afforded by the degraded flowers, which in certain genera are borne together with ordinary flowers, makes the following observations bearing on the question here discussed, viz., whether or not to include Alcippe amongst the Lepadidæ. “Ces exemples peut-être aideront à comprendre comment à des genres d’une organisation assez compliquée, viennent quelquefois s’en rattacher d’autres d’une organisation beaucoup trop simple en apparence, membres appauvris et dégradés d’une même famille, qui lui appartiennent sans la représenter; comment le type, s’y présente comme effacé, ne conservant plus pour se laisser reconnaître que quelque trait isolé, mais caractéristique, dont la valeur, essentiellement ordinale, peut être ainsi constatée.” Under the point of view, so strongly and admirably insisted on lately by Milne Edwards (‘Annales des Sciences Nat.,’ 3d series, tom. 17), of describing types without regarding whether the different members blend together on their confines, perhaps Alcippe should be raised to the rank of a Family: I feel quite unable to decide how properly to act.

But we shall presently find, when we come to Cryptophialus, that all the above difficulties, great as they are, are greatly enhanced, for Cryptophialus is certainly allied in a very direct and curious manner (in decided opposition to the remarks just made on special affinities) to Alcippe, and yet in all the more important parts of its organisation, and in its metamorphosis, it differs so fundamentally, that I have felt myself obliged to form not merely a Family, but a distinct Order for its reception.

 

Genus — ALCIPPE. Pl. 22, 23.

ALCIPPE. Hancock. Annals and Mag. of Nat. Hist., vol. 4, 1849, Pl. 8, 9.

Fem. — Capitulum without valves, with the orifice spinose: peduncle with the basal end added to during growth; its rostral surface depressed and covered by a horny disc: capitulum and peduncle imbedded in a cavity excavated in the shells of molluscs.

Labrum very large, with a row of long hairs on each side: palpi rudimentary: mandible one-toothed: second, third, and fourth cirri absent: fifth and sixth cirri with the posterior ramus represented by a button-like body: caudal appendages four jointed, muscular: anus none.

Males, — several, adhering to the upper end of the horny disc of the female: capitulum naked, transparent, elongated, with a small orifice at the end: peduncle lobed, with the lower end extending far beyond the pupal antennæ: eye, testis, and vesicula seminalis single; probosciformed penis very long: mouth, stomach, thorax, abdomen, and cirri none.

 

 

ALCIPPE LAMPAS, Hancock ut suprà.

Hab. — North-eastern shores of England, fifteen to twenty fathoms, imbedded in dead shells of Fusus antiquus and Buccinum undatum (A. Hancock); south-eastern shores, off the Eddystone, Lighthouse (C. S. Bate).

FEMALE. Pl. 22.

I may premise that after the sketch of the leading peculiarities of Alcippe, and after the discussion on its affinities, just given under the Family, I think it would be superfluous to institute a full generic description, separately from the following detailed account of this most anomalous cirripede.

General Appearance. — The whole animal is from .2 to .3 of an inch in length, of a soft texture, colourless or yellowish, and lives concealed in a cavity of its own formation in the shells of certain Gasteropods. This cavity communicates with the water by a narrow fissure-like orifice (Pl. 22, fig. 4), broadest at the posterior end, where the cirri are exserted; narrow, closed, and generally curved at the other (a) end: the two sides of the fissure (b) are commonly bordered by a calcareous inorganic deposit: the walls of the cavity are worn so thin over the peduncle, at the narrow end of the fissure, that the orange-coloured ovaria can generally be seen through the shell of the mollusc, and hence there is here a distinct fan-shaped stain (fig. 3) on the surface. The animal consists of a compressed capitulum, without valves, and of a sort of peduncle depressed on its rostral face, and covered with a broad, oval, thin, horny disc. We must remember that in the Lepadidæ the peduncle does not essentially differ from the capitulum, being only the flexible lower or anterior end of the animal, and is separated from the capitulum only by shape, and generally by the direction of the lines of growth. The disc, when most regular (fig. 1, H), lies in a plane at right angles to the sides of the capitulum, and almost in a line with the orifice leading into the sack; but the peduncle is often very irregular (fig. 2), and the disc comes even to occupy a position nearly parallel to one or the other side of the capitulum. On the carinal side, the capitulum is generally separated from the peduncle by a rather deep fold (f, in the section fig. 5), but this depends in some degree upon the state of distension of the mass of ovarian cæca. I have given a drawing, fig. 1 (partly taken from Mr. Hancock), of a very regular individual, and of an extremely distorted specimen (fig. 2). The distortion, I believe, is generally caused by the animal, during its excavation, breaking into some old cavity.

External Structure. — The orifice leading into the sack is about one third of the total length of the animal: its edges or lips are thickened, horny, and brownish: at the lower end, exactly where the orifice ends, the lips are formed, from being deeply notched, into two sharp projections (a, figs. 1, 5, 6), unlike anything occurring in any other Cirripede. The external membrane (c, fig. 6) of the lip supports an irregular but nearly straight band of sharp, thick spines of chitine, about 1/1000th of an inch in length, together with a few hairs: at the carinal or upper end of the orifice the spines are largest and most numerous; at the other and lower end, they decrease in size; and on the two projections (a, fig. 6), and on the adjoining parts of the external membrane, they graduate into the small dentated points which cover the whole surface of the animal. The inner tunic of the sack (b), on each side along the upper half of the orifice, is remarkable from having a moderately broad, curved band of short, sharp spines, not quite so thick as those on the external surface, closely adpressed together and pointing upwards, like the javelins of an ancient phalanx, thus probably preventing the ingress of any intruding animal. This band of spines curves at the upper end, conformably with the shape of the orifice. The inner tunic of the sack in this upper part is yellowish, and, what is very unusual, is thicker than the external membrane. A little way down, within the orifice, and more especially in front of an elegant row of hairs on the two sides of the great labrum, there is a band of very fine but stiff hairs (5/1000ths of an inch in length), pointing upwards, and making together with those on the labrum a hedge, barring ingress into the sack.

 

The external membrane over the whole animal, excepting the horny disc which covers the rostral face of the peduncle, is very thin and transparent; it is periodically and often moulted, as may be inferred from the many old lines of junction round the edges of the horny disc: it is irregularly and pretty thickly (but not so thickly as in fig. 7) studded with star-headed, minute points, from 2 to 5/10,000ths of an inch in diameter, composed of hard chitine, seated on a short footstall, and this on a circular, yellowish, slightly thickened disc of the general investing membrane, appearing like a halo surrounding each little point. These points are directed obliquely upwards. There are none on the horny disc, though particularly numerous close to its margin. Their state varies much: just after a moult, when newly formed, the spines are regularly star-headed, with quite sharp rays, from two to six in number, with some of them occasionally bifid; but these points or rays soon become blunted, and ultimately half the star is worn away, so that the appearance then presented is that of a crescent with a few blunt points on its convex side. At each exuviation, the thickened membrane of the orifice with its strong external spines (the condition of which also varies according to the period elapsed since the last moult), and of course the whole internal tunic of the sack, with its spines and hairs, are all moulted, together with the external membrane and the little star-shaped points. In most specimens a barely distinguishable band or bar of yellowish, slightly thickened membrane, runs from the points (a), at the lower end of the orifice, for some way obliquely downwards; and at the lower end of this bar the weak adductor scutorum muscle (having transverse striæ) is attached. This bar is often strengthened by a prominent external fold of membrane, but yet it is so flexible, and as it is united only to the lower end of the orifice, I can hardly believe that it can, by means of the adductor muscle attached to its opposite extremity, have much power in closing the orifice. I believe that this muscle acts simply in narrowing the whole animal, so as to favour its movement within the cavity in which it is imbedded. Owing to this position of the adductor muscle, and its consequent little power in closing the orifice, we can understand the necessity for the defence afforded by the bands of spines and hairs on the inner tunic of the sack and on the labrum, which do not occur in other Cirripedes.

Horny disc. — The general shape of the disc, its irregularity and position, have been already described. It never extends, as remarked by Mr. Hancock, to the extreme lower point of the peduncle; upwards it reaches to a little below the lower end of the orifice. It consists of successive layers of membrane, either moderately thick and opaque, or only a little thicker than the general membrane of the body, but never furnished with the little sharp points; it increases in size, in like manner as the calcareous valves of other Cirripedes, the undermost and last formed layer extending beyond the others, with its edge united, till the next exuviation, to the general membrane of the body. The disc is attached, at its upper end, apparently in the usual way, by cement, to the roof of the cavity of the shell in which it is imbedded; but the lower parts of the disc are also slightly and partially attached, chiefly along the lines of growth or exuviation; and this, I suspect, is effected by an inorganic calcareous deposit; anyhow I could not perceive here any cement or cement-ducts. Beyond the circumference of the disc the whole animal lies free in its cavity. The lines of growth in the middle part of the disc are generally obliterated by the decay of the older and outer layers. These lines, though of course ordinarily conformable with the general outline of the disc, are not always so, for the disc sometimes becomes during growth slightly changed in form, and the animal, consequently, slightly changed in position; sometimes either one or the other side or the upper end of the disc is left deserted by the new layers of the growing disc; these being formed on the deserted side of less size or extension, instead of larger size, as they normally should be all round the disc.

The upper end of the disc is always produced into a projection of not regular shape, but generally hollowed out or embayed in front (fig. 1), and almost always hollowed out on the two sides. This projection stands directly over the adductor muscle (b in fig. 5), and on the exterior surface is generally convex, being concave on the under side for the attachment of several muscles presently to be described. The horny layers are in this part usually thicker than elsewhere. The disc is thus upwardly produced, owing apparently to the fissure which leads into the cavity of the shell of the mollusc becoming, during the process of excavation, considerably longer than is necessary, — that is longer than the orifice leading into the sack; and consequently, for the protection of the imbedded animal, the lower and narrow end of the fissure is closed on its under side by this upward production of the horny disc, formed of layers of membrane of unusual thickness. A deposition, also, of lime, hereafter to be mentioned, gives further protection.

In the bays on each side of the upward production of the horny disc, and likewise a little lower down on its edges, and therefore somewhat protected by lying within the narrow, pointed, lower end of the fissure in the shell of the mollusc, the short-lived Males (Pl. 22, fig. 1, m) are attached often in groups of two, three, or more together.

It may be asked to what part, in other Cirripedes, does the horny disc answer? Not considering the upward prolongation, which has been developed for a special purpose, the disc is irregularly circular, — is added to all round, — serves for the attachment of the whole animal to the supporting surface, — is covered on the under surface by a conformable and parallel mass of ovarian cæca, and the latter by the inner tunic of the sack; therefore in every character, and in its relation to the other parts of the animal, the disc answers to the end of the peduncle, or to the basal cup in Lithotrya, or still more closely to the basis in sessile cirripedes, with the important exception that it lies in a line with the longitudinal axis of the whole animal instead of at right angles to this axis. We know that all ordinary cirripedes become first permanently attached in their pupal state by their antennæ, which are seated on the ventral or rostral surface, near to the anterior end of the body; and that from the young cirripede, after the act of metamorphosis, being turned vertically upwards, and from the extreme anterior, now lower, end of the body not being rapidly developed, the surface cemented down, or the basis, encroaches almost equally on the dorsal, lateral, and ventral surfaces. But if we were to suppose the extreme anterior point of the body to be rapidly developed, the surface of attachment or basis, without it grew still more rapidly, could not possibly reach the dorsal surface, and would, consequently, be confined to the ventral or rostral surface. I have not seen the young of the ordinary or female Alcippe soon after its metamorphosis, but in the male the development of the extreme anterior end of the body is extraordinarily rapid, and from analogy we may fairly conclude that this is likewise the case with the female. Hence I believe that the horny disc answers to the cemented down, lower end of the peduncle, in other members of the Lepadidæ, and to the basis in the Balanidæ, and that it is confined to the ventral or rostral surface, owing to the anterior or lower end of the body having been rapidly developed. To make all the parts, internal and external, of Alcippe, correspond with those of other cirripedes, the main circular part of the horny disc must be turned up at nearly right angles to its present position (the dorsal or carinal integuments, to the right-hand in fig. 5, being shortened), and then we should have a peduncle, certainly very short and broad, but holding its proper relative position.

In the genus Lithotrya, as long as the animal continues to bore into the rock, the calcareous discs by which it is attached in its cavity, stand, as in Alcippe (Pl. 8, fig. 2, 2 a′, Darwin’s ‘Monograph on the Lepadidæ’), parallel to the longitudinal axis, but as soon as the animal ceases to bore, and the discs become converted into a cup, they occupy a normal position at right angles to the peduncle. According to Reinhardt, these discs, in Lithotrya, are situated on the carinal or dorsal surface of the peduncle, at which statement I now feel considerable surprise, as undoubtedly the pupa must first permanently attach itself by its prehensile antennæ on its ventral or rostral surface. In Anelasma I failed to discover any cement or cement-ducts; but I am now strongly inclined to believe, considering that the extreme lower or anterior end goes on growing, that the surface of attachment will be found to occur, as in Alcippe, on the rostral surface, a little way below the orifice.

Sack and its Muscles. — I have already described the curious phalanx of spines, the long fine hairs, and thickened condition of the inner tunic of the sack along the sides of the orifice. This inner tunic is a reflexion from that enveloping the body of the animal, in the usual manner, as may be seen in the section (Pl. 22, fig. 5). Between the external membrane and the inner tunic of the sack (e), there is of course the usual double fold of corium, these two folds being united by minute, transverse, ligamentous fibres, branched at the two ends, as in other Lepadidæ. Imbedded in the corium there are numerous, longitudinal, striæ-less muscles, which do not run quite up to the orifice, but to an oblique line beneath it. Externally to these muscles there are, as in the other Lepadidæ, fine transverse muscles, confined to the middle part of the animal, and running from the carinal margin more than half way round both sides. Attached to the upper notched or folded end of the orifice (g, fig. 5, above the upper ends of the longitudinal muscles), there is a fan of rather strong, striæ-less muscles, expanding downwards, with their lower extremities attached to the outer membrane of the capitulum; these muscles apparently serve to open the orifice: there is a somewhat analogous muscle in Lithotrya, but in no other member of the Family: in Cryptophialus, however, there is a closely similar muscle. Owing to the action of these several muscles, the tissues forming the capitulum and peduncle are, according to Mr. Hancock, highly contractile.

I have stated that the under surface of the upper produced end of the horny disc is concave, and serves for the attachment of several muscles. Of these some run to the basal margin of the great labrum, and no doubt, as usual, move the whole mouth; others, as usual, run to the skin between the labrum and the lower end of the orifice, — i. e. in fig. 5, between the lower end of the row of fine hairs (see fig. 11), which shows where the basal margin of the labrum is situated, and the lower side of the point (a), where the orifice terminates: others run obliquely on both sides towards the point of attachment of the small adductor scutorum muscle (b, fig. 5): others, of considerable strength, and these are more peculiar, run and are attached to the lower end of the orifice (a), and serve apparently to draw up the orifice from within the fissure-like cavity, in which it lies lodged: others, again, extend transversely on both sides, close beneath the inner tunic of the sack, a little beyond the line whence the ovigerous fræna or branchiæ arise. These transverse muscles lie within the longitudinal muscles, and therefore are quite different from the exterior transverse muscles, which are situated more towards the carinal portion of the peduncle and capitulum, and which are common to most Lepadidæ. The internal transverse muscles, and those running to the lower end of the orifice, are peculiar, but we shall hereafter meet with them even more developed in Cryptophialus.

Along the medial carinal line there is, between the two layers of corium, the usual circulatory channel. On each side of this line, on the inside of the sack, there are generally some slight irregular swellings, and sometimes a large extent of the inner surface is irregularly carunculated with little knobs. The sack (e in fig. 5) extends down almost to the basal point of the peduncle (d), more especially when the ovarian cæca are not gorged with ova.

Branchiæ, or ovigerous Fræna. — Within the sack, on each side of the body, rising not far from the ends of the adductor muscle (b), there is a large fillet or fold; the two occupy so exactly the position of the ovigerous fræna that I cannot doubt such is their nature, though, as happens in the case of some species of Pollicipes, they are destitute of their proper glands, and so do not serve for the attachment of the ovigerous lamellæ; this attachment probably is not required, owing to the protected situation which the lamellæ hold in the sack, under the animal’s body, and over the ovarian cæca. From the unusually large size of these so-called fræna, I cannot doubt that they serve as branchiæ, equally well with the plicated folds of membrane, believed to be homologous with the fræna, in the Balanidæ, which have by every one been considered as branchiæ. The fræna are broad and truncated at their upper ends; their margins are sinuous, and their outer surfaces papillose; they run longitudinally down the sack, narrowing as they extend, almost to the basal point of the peduncle, and hence are of considerable length; they are hidden in the section (fig. 5) by the medial, somewhat protuberant mass (c) of ovarian cæca, and partly by the (i) prosoma.

Body. — The body is constructed on the usual type, and indeed does not differ greatly from that of Ibla. The labrum is very large, its lower or basal margin is separated by an unusual space (capable of being contracted or folded) from the lower end of the orifice of the sack; hence the labrum and whole mouth is placed quite remarkably near the upper (or carinal) end of the orifice. This upper end of the orifice, I may remind the reader, is homologically the posterior end of the general covering or carapace, and all that portion of the whole animal (as the sectional figure, 5, stands) below the lower margin of the labrum, on the rostral or ventral surface, is formed by the three anterior segments of the head. The main part of the body, carrying the mouth, is formed by the great development of that segment of the thorax which bears the first pair of cirri (h), here closely adpressed, as usual, to the sides of the mouth. The lower portion of this segment forms the prosoma (i), and has the characteristic outline, but is not much developed. On each side of the prosoma an oval space of membrane is yellowish and is thickened, and so gives support to this part of the body. The five succeeding thoracic segments, which ought to carry the five succeeding and posterior pairs of cirri, are together of very small size (as in Ibla), in comparison with either the prosoma, or the whole anterior part of the animal. The segment (k) which should have borne the second pair of cirri, is considerably longer than the following segments, and is at the same time less distinct, owing to an oval convex shield of thickened membrane on the sides, not extending the whole length of the segment, thus causing two transverse creases, which, when the thorax is contracted, appear like two additional segments. Had this segment borne cirri, they would have stood, as in Ibla, at a considerable distance from the first pair. The segments (l, m) which should have borne the third and fourth pairs of cirri are like each other, except that the former is rather the longest. The membrane covering all the thorax is surprisingly thin; and at the articulations, which are straight and transverse, is deeply folded, so that the thorax must be highly extensible, to a degree which I have not seen equalled in any Cirripede except in the males of Scalpellum vulgare and ornatum. The thorax is represented as somewhat extended in fig. 5. This part of the thorax is amply furnished with striated and striæ-less muscles for its retraction and protrusion, and for lateral movements. The segment (m) which should have borne the fourth pair of cirri, at first sight falsely appears like the terminal segment of the thorax: in one monstrous specimen it bore a single cirrus, showing (if there had been any doubt) that it was a true segment. The three terminal pairs of articulated appendages, form together a brush; they consist of the fifth and sixth pairs of cirri and of the caudal appendages: my reasons for considering the last-named organs as of caudal origin will be given hereafter. A moderately careful inspection, especially of the ventral surface, will show that the fifth pair of cirri are borne on a small segment (n, fig. 5, but plainer in fig. 13), which is quite distinct from, but partially concealed by, that which ought to bear (and did bear in the monstrous case) the fourth pair of cirri: this segment is oblique, and cannot be traced distinctly all round the dorsal surface. The segment (o, fig. 13) bearing the sixth pair is much less distinct, and can only be seen by a longitudinal section, or when the cirri are a little separated, but it certainly exists, as is likewise shown by the presence of small apodemes dipping in amongst the muscles, between this and the last segment. The posterior or caudal appendages are closely approximated; they are not separated by any fold from the sixth thoracic segment; but appear as if they were articulated on the dorsal surface of the sixth pair of cirri, in exactly the manner usual in the other Lepadidæ. The segments bearing the fifth and sixth pairs of cirri are highly oblique to the preceding segments, and consequently the cirri, which they support, instead of projecting inwards, lie like a brush in a line with the longitudinal axis of the main part of the thorax. The membrane forming the two small oblique terminal segments of the thorax is strengthened by irregularly shaped plates of thicker and yellowish membrane.

In the middle, the fold is slightly prominent and pointed, and being most finely villose, I for some time looked at this projection as a rudiment of the probosciformed penis.

Mouth. — The mouth is constructed on the strictly normal type of the Family, but is peculiar in every part; it is remarkable from being situated so near the upper (or posterior) end of the capitulum, this being caused by the great length of the labrum, and of the space of body between the latter and the lower end of the orifice. The labrum is a very singular part of the mouth from its vast size and outline: in fig. 8, we have a front view of the mouth, of which the whole upper pointed part consists of the labrum, and h h is the first pair of cirri; in fig. 11, we have a lateral view of the labrum, with the surrounding thin membrane of the body, a — a, still adhering to its edges; h is the first cirrus on the near side; m the mandible, a little distorted in order to show its tooth, marking the position of the transverse crest of the labrum and of the orifice of the œsophagus; b b is the medial longitudinal ridge of the labrum. In the Balaninæ the labrum forms a mere rim to the back of the mouth, consisting of an inner fold running down the œsophagus, and of an outer fold, both close together: in the Lepadidæ the folds are separated, the outer one being swollen or bullate; and here this structure is carried to even a greater extreme than in Ibla and its allies. The distance between the transverse crest over the œsophagus and the blunt projecting point on the summit of the medial ridge, b b, equals twice the longitudinal diameter of the rest of the mouth. The lower margin on each side of the labrum is produced into two projections (fig. 11), the longer one curling round to a point beneath the jaws, with its extremity imbedded as an apodeme. Another very peculiar character in the labrum, prominently noticed by Mr. Hancock, is caused by a longitudinal row, on each side, of closely approximate, long, very finely pointed hairs, which, as already stated, are fronted on the opposed internal surface of the sack by an irregular band of still finer hairs. The surface of the labrum is partially covered by minute toothed scales, and these, seen on the longitudinal medial ridge, b b, give it a finely denticulated structure. At each end of the transverse crest which overhangs the œsophagus, there is a knob, such as occurs on the labrum of every Cirripede. United to these two knobs, which are formed of thick and yellowish membrane, and springing from the adjoining sides of the mandibles, there are two swellings formed of thin membrane (fig. 8), which occupy the exact position of the palpi, and may be considered as these organs in a rudimentary condition and destitute of bristles.

 

The mandibles are simpler than in any other Cirripede; they are minute; they consist of an oblong plate, with only one very strong tooth at the upper end: the face towards the labrum is swollen: beneath the upper free part there is a small, sub-triangular piece of thickened membrane, let in and forming part of the general outer surface of the mouth, and representing the large square plate found in other Cirripedes. The maxillæ (fig. 15) are smaller but broader than the mandibles; they have an upper tooth and a smaller lower one, lying not quite in the same plane with the upper one, but nearer the mandibles. The apodeme (fig. 8, 15) is of remarkable length, extending beneath the basal fold of the mouth: it does not arise from the ridge or outer edge of the maxilla, but a little on one side, from the face directed towards the mandible. Between maxillæ and mandibles there is a very singular prominent fold of membrane (fig. 8, 15), which resembles, but probably falsely, the supposed rudimentary palpus attached to the mandible. Altogether the maxillæ differ considerably from the same part in other Cirripedes. In structure they seem adapted to assume the function of mandibles; but they do not stand directly over the œsophagus. The outer maxillæ (fig. 8) appear like a minute, deeply notched lower lip: each consists of a simple, oblong, rounded plate, with a few small bristles at its upper end. The basal fold of the mouth in front, beneath the outer maxillæ is distinct, and runs in a line with the basal articulation of the first pair of cirri. In the rudimentary palpi, minute and little developed outer maxillæ; and in the inner maxillæ, taking the function of the mandibles, the mouth of Alcippe presents some resemblance with that of Anelasma.

Cirri. — These consist of the first, fifth, and sixth pairs: the other pairs are absent, except in one monstrous specimen, in which there was a fourth cirrus quite like the fifth. First pair, fig. 14, these are seated on each side of the mouth in the usual position. They are formed of very thin and flexible membrane. The pedicel, as usual, consists of two segments, the upper one is short and not very distinct; but when viewed on the inner side can be seen to have the ordinary structure: both segments are destitute of bristles. There are two short rami, being about one third of the length of the pedicel: they are directed either in the line of the pedicel, or more commonly posteriorly, that is towards the other cirri, and therefore in an unusual direction. The anterior ramus is generally rather longer and thinner (as is commonly the case with other Cirripedes) than the posterior ramus; but there is some variation in this respect. On neither ramus is there any trace of the ordinary articulations: both are thickly clothed with fine bristles, which are singular from being thickened in their lower parts, and plumose, like a feather. These cirri have some resemblance, as remarked by Mr. Hancock, to a pair of pincers; but they cannot act as such; they serve, I believe, as brushes. Delicate muscles, transversely striated, enter and are attached within both rami and within both segments of the pedicel, on the usual type, showing that these organs (if there had been any doubt) are truly cirri.

The fifth and sixth pairs of cirri (fig. 13, n′, o′) are almost exactly alike: they are of very small size: each cirrus consists of four segments: the lower or basal segment is broad, with a few minute bristles scattered on its inner surface: the second segment is also broad, but shorter, with a few, generally hooked bristles, in two short irregular rows, in the upper part: these two segments answer to the two segments of the pedicel of ordinary cirri. The third segment is thinner and longer than the second; it bears two or three longitudinal rows of bristles, most of which are neatly hooked at the point; its upper end is surrounded with a circle of bristles. The fourth and terminal segment is short, thin, and simple, with only a few bristles at the apex. These two upper segments are bent a little inwards; they answer to one of the two normal rami of ordinary cirri. The third segment does not stand exactly on the middle of the summit of the second segment, — the posterior corner of the latter being occupied by a very curious, convex, oblong, rather hard (especially in the lower part), protuberant cushion (as called by Mr. Hancock) or button (fig. 9, c′), transversely wrinkled by fine, distinctly crenated ridges. This button presents a considerably different appearance according to the point of view, fig. 9, 10: on one of its sides it projects beyond the outline of the second segment, whence it arises; on the other side it is prolonged, as a smooth ridge, on the top of the second segment, embracing to a certain extent the base of the third segment. On the face opposite to that which has been drawn (fig. 9) as most characteristic, it is seen to be somewhat constricted round its base; this constriction, representing, I believe, an articulation. When viewed directly in front (fig. 10) its outline is oval, passing into shield-shaped. Its longitudinal axis is 3/1000ths of an inch in length; but it varies a little in shape and size. I shall presently assign my reasons for believing that these buttons are the posterior or inner rami of the fifth and sixth pairs of cirri in a rudimentary and much modified condition.

Caudal Appendages. — These (fig. 13, p) are placed close together, being articulated between the bases of the sixth pair of cirri, the lines of junction being internally marked by minute apodemes. They consist of four segments, resembling in every respect those forming the cirri, with the important exception that there is not a vestige of the button on the summit of the second segment; the segments are not so thick as those of the cirri, and the terminal segment is smaller.

Muscles and Functions of the Cirri. — For their size, the cirri and caudal appendages have voluntary muscles of remarkable strength, attached within their basal segments, and springing from the dorsal and ventral surfaces of the so-called third and fourth (l, m) thoracic segments. Other muscles, rising from within the basal segment of each limb, run to the second segment, and from that to the third segment. I could not distinctly make out whether any entered the terminal segment. I have seen no other instance of muscles entering the caudal appendages, but as in the pupa they are so furnished, we here have only an embryonic character preserved. I may remark that the fifth and sixth cirri, consisting of two large basal and two thinner terminal segments, is likewise an embryonic character. From the position of the cirri, the four hard protuberant buttons or cushions, tend to oppose each other at a common point; and the caudal appendages fill up a gap behind, between the cirri of the sixth pair. I at first thought, with Mr. Hancock, that these buttons served to catch the prey; but, reflecting on their convexity and hardness, they appear very badly adapted for this purpose; it would, in fact, be a marvellous feat to secure, in the dark, any moving object between four balls. On the other hand, this very convexity, the hardness, and especially the crenated ridges, and the powerful muscles (which from the first surprised me), are all well explained, if we suppose the prey, being secured by the terminal segments, to be triturated between these four balls: any part which escaped upwards would, moreover, be retained in a sort of cage, formed by the inwardly inflected terminal segments with their hooked spines. This view of the very curious and unparalleled use made of a modified portion, not of the haunch, but of an upper part of the two posterior pairs of thoracic limbs, is in some degree confirmed by finding that Cryptophialus, which has apparently analogous habits, requires its food to be triturated, though in this case it is effected by very different means, namely, by four beautifully toothed discs, with brushes of hairs, developed within the lower end of the œsophagus.

The prey, when caught, would probably at once be carried by the movement of the articulated thorax to the mouth (itself moveable), and being there secured by the mouth in front, the caudal appendages behind, the tips of the cirri above, and the broad pedicels of the first pair on the two sides, it would be triturated by the four crenated buttons, and would then be forced down the œsophagus by the action of the simple jaws. I looked in vain in several specimens for any object within the stomach. I believe, that when the specimens are first taken, all half digested food is ejected by the mouth. Whether we may thus account for the extremely foul condition of the rami of the first cirri in all the many specimens examined by me, I know not; but that these rami, which are thickly clothed with fine plumose hairs, and are furnished with delicate muscles, act as brushes, so as to clean the orifice of the sack, I can hardly doubt.

Homologies. — I have as yet, to a certain extent, assumed that I have correctly named the different parts; and a few remarks on this head may be desirable, considering the absence of certain cirri, the singular condition of the others, the close general resemblance of the cirri and caudal appendages, and the fact of the latter being furnished with muscles. The only cause for any doubt regarding the thoracic segments is the shield of thick membrane on that segment (k, fig. 5), which ought to have borne the second pair of cirri, causing two transverse wrinkles (not distinguishable, however, on the ventral surface), and sometimes making the segment appear as if it consisted of three segments: if it did consist of three, as there can be no doubt about the nature of the first pair of cirri, (not in a more rudimentary condition than in Anelasma) or about the segment whence this first pair arises, the two terminal oblique segments, with their appendages, would be abdominal instead of thoracic: but this is improbable, inasmuch as the abdomen is unusually little developed in the pupa (as presently to be shown), and more especially from the circumstance of a monstrous cirrus, identical in structure with the two succeeding pairs, having been borne on a segment (m), which, in any case must be considered as thoracic, for it is well known how very rarely thoracic and abdominal limbs resemble each other. I cannot myself feel hardly any doubt on the nature of these three pairs of appendages; for, in the first place, the posterior appendages are articulated on and between the bases of the adjoining pair, exactly as the undoubted caudal appendages are articulated in all other members of the family on the sixth pair of cirri or terminal thoracic appendages. Secondly, we see in the male of the allied genus Ibla, the very same appendages preserved as in Alcippe, namely, the caudal, and the fifth and sixth pairs of cirri, which latter, moreover, are generally uniramous. Thirdly and lastly, in the likewise allied Alepas cornuta, we have the posterior rami of these same fifth and sixth pairs of cirri in a rudimentary condition, and resembling in every respect the caudal appendages. Assuming, then, that the several appendages in Alcippe have been rightly denominated, we have to consider the nature of their segments: in all cirripedes, the pedicels of the cirri consist of two segments, of which the lower one (as here) is longer than the upper one, and both (as here) considerably thicker than the segments of the rami: in all cirripedial pupæ, likewise, the thick pedicels of the limbs consist of two segments, and each ramus, also (as here), of two segments: now, with these coincidences, and bearing in mind that in Alcippe the two upper segments do not arise from the exact middle of the summit of the second segment, but from rather its anterior side, — bearing, also, in mind the case just cited of Alepas cornuta with the posterior rami of these very same cirri rudimentary, — we may, I think, safely conclude that here in Alcippe the two lower segments form the pedicel; the two upper segments, the anterior ramus; and that the button-like protuberance is the posterior ramus in a modified condition. As the caudal appendages in none of the Lepadidæ, either in the mature state or in the pupa, have two rami, we can satisfactorily understand the absence of any trace of the button-like protuberance on the top of the second segment.

I almost wish I could persuade myself that I had taken an erroneous view of the thoracic segments, and therefore that the three pairs of terminal appendages were all abdominal, for then Alcippe would come into much closer relationship with Cryptophialus; though even in that case it would form a distinct family from it: but I cannot alter my opinion.

Alimentary Canal. — The œsophagus runs down from the mouth, beneath and nearly parallel to the straight row of hairs on the two sides of the labrum: it is surrounded by the usual muscles: at the lower end it bends down, and expanding a little, like a bell, enters the stomach. The stomach is of considerable size and fills the main part of the body, bulging out under the mouth, and prolonged as far as about the middle of that segment (l), which ought to have borne the third pair of cirri; here the stomach terminates in a blunt rounded point. The tissue surrounding the stomach, and keeping it in its proper place, can be traced to the posterior end of the thorax, but there is no rectum or anus. I am prepared to assert positively that this is the case, for I made repeated longitudinal sections of the whole thorax in two planes, and I subsequently cleaned the outer tissues with boiling potash, and then, when as transparent as a sheet of glass, I examined every part, and certainly there is no rectum (which in every case is formed of chitine, and so is not acted on by potash) nor an anal orifice. Singular as this fact is, it is not so improbable as it at first appears; inasmuch as I have shown, in my former volume, that the Lepadidæ can reject half digested food by their mouth, and secondly, that the final stage of digestion appears to take place in the upper part of the stomach. In the male of this very species, as we shall immediately see, there certainly is no mouth or stomach, and apparently no rectum or anus; so is it likewise with the males of Scalpellum vulgare and ornatum: in Proteolepas, there is a mouth and an œsophagus, but no stomach, rectum, or anus. There are, I believe, no other known instances, in the whole great class of Crustacea, of the absence of an anus.

I may venture to remark that I succeeded in every attempt, which I made, in seeing plainly the œsophagus, and the acoustic and olfactory orifices and sacks, which, according to all analogy, would be of much smaller size, and far more difficult to discover, than the rectum and anus. I may mention that, according to Mr. Newport (‘Annals of Nat. Hist.,’ 1849, ), the larvæ of certain parasitic Hymenoptera have a stomach without any anus. No crustacean, according to Milne Edwards, is destitute of this orifice.

The stomach, in Alcippe, is much corrugated, so as to be deeply pitted; but there are no regular cæca. The enveloping hepatic layer is thick, brownish, pulpy, and formed of pellets of cellular matter, not distinctly arranged in lines as is general; there is the usual delicate muscular layer. The stomach was in every case empty, and I did not notice the separated epithelial coat, so generally found in other cirripedes.

Organs of Sense. — I failed in discovering the eye, which I have no doubt exits, as it is conspicuous in the pupa and in the male. The olfactory pouches are seated rather laterally under the maxillæ, as in Ibla. As in this same genus, the acoustic sack is seated remarkably low down (fig. 5), at a very considerable distance beneath the basal articulation of the first cirrus: the orifice is seated on a slight prominence: the acoustic vesicle, I believe, is sub-cylindrical, with irregular projections. I did not make out anything distinctly on the nervous system.

Female Generative System. — The animal we have thus far described is exclusively female: when a longitudinal section of the thorax is made, and the stomach removed, it can be most plainly seen that there are no vesiculæ seminales or testes. Mr. Hancock has remarked on the absence of the usual probosciformed penis. The male of Alcippe will be subsequently described in detail. The female organs differ in no respect from those of other members of the family, excepting in so far that the layer or mass formed by the ovarian cæca (c) does not lie transversely to the longitudinal axis of the whole animal, but longitudinally under the horny disc. The ovigerous fræna are largely developed, but serve, as previously stated, as branchiæ, and not for their proper function of giving attachment to the ovigerous lamellæ. The ovigerous lamella is single, and nearly corresponds, in size and shape (as would ensue from the manner of its formation) to the under side of the horny disc. The ova are broadly oval, and rather above 1/100th of an inch in length.

Metamorphoses. — The larva in the first stage has been fully described and figured by Mr. Hancock: it differs in no essential respect from other larvæ of the family. Mr. Hancock overlooked the inferior minute antennæ. With respect to the larvæ in the last stage, or pupa, I obtained several specimens attached to the disc of the female, and which were on the point of being developed into males; and another specimen identical in all respects, but attached independently to the shell of the mollusc, and which, therefore, I have every reason to suppose, would have been developed into a female. In any case these pupæ may be conveniently here described (Pl. 23, fig. 16.) They are .025 of an inch in length; they are of the usual shape, with the anterior end not very blunt and the postero-ventral surface somewhat produced. The whole carapace or shell is very thin and smooth. There are six pairs of thoracic natatory legs, situated far back towards the posterior end of the body; each leg has the usual articulations, and the two rami their usual long but not plumose spines; the presence of the legs deserves notice, considering the rudimentary and modified state of their homologues in the mature animal. The abdomen differs considerably from the same part, as far as I have seen, in other pupæ; it consists of only a single almost globular (fig. 17, q) segment, instead of three segments; and the two caudal appendages (r) are very long, and are composed each of only a single segment (instead of two), carrying at its tip two short spines. There are two purple eyes, 4/3000ths of an inch in diameter, which, after having been dried and then soaked, could be seen to be compound; they are fixed in the usual manner to two rather short apodemes, which latter have their usual origin. But the pupa has a very unusual appearance owing to the presence of a single dark purple eye, half the diameter of the two larger eyes, situated behind and above the latter, and quite disconnected with the apodemes; this is the eye of the mature animal, which, for some reason, is here developed earlier than usual. The prehensile antennæ are remarkable from being seated very close to the anterior extremity: owing to this, the articulation of the second or main segment with the basal segment, is hardly at all oblique. The whole pupa is of exactly the same length as the pupa of Ibla quadrivalvis, and so are the antennæ, (see  of my volume on the Lepadidæ), viz., 32/6000th of an inch, but the second segment is narrower, (being only 8/6000ths in breadth in the broadest part), and is longer in proportion, for the disc which forms part of the total length is only 4/6000ths in length, whereas in Ibla it was 8/6000ths; the disc is here hoof-shaped, as in Ibla. The ultimate segment is remarkably short and narrow, (being only 3/20000ths in width, and less than half the size of that in Ibla); it carries (I believe) three terminal spines, and is not notched. Altogether the antennæ more nearly resemble those of Ibla than of any other genus in the family. From the position of the antennæ, and from the length of the second segment, the pupa, when cemented by the disc or third segment, to the supporting surface, adheres, with its posterior end almost vertically upwards. With respect to the young cirripede within the pupa, I could only observe that its anterior end was formed into a blunt point.

Powers of Excavation; Inorganic Deposit of Calcareous Matter; Attachment. — Alcippe, according to Mr. Hancock, attacks only dead shells of the Fusus and Buccinum, and always on their inner sides, especially on the columella. The excavations, in the specimen which I examined, were so numerous as almost to touch, and sometimes to run into each other, the included animal being thus rendered distorted. The orifices are directed with respect to the shell indifferently upwards or downwards. From the shape and size of the cavity corresponding to that of the included animal, there can be no doubt, as stated by Mr. Hancock, that Alcippe forms its own cavity. That the action is mechanical I think may safely be inferred from the whole outer membrane being studded with minute, star-headed points of hard chitine, which rise from halo-like little discs of thickened membrane, which latter are well adapted to allow the underlying adherent muscular layer to act on the points, and thus on the surrounding shell. Consequently the points generally show signs of severe attrition, but they are periodically and often replaced, at each exuviation, by new and much sharper points. There are no points on the permanently attached layers of the horny disc, but it particularly deserves attention, that the renewable membrane always extends beyond the circumference of the disc, and is there most thickly studded with the points. We have met, in Lithotrya, with a precisely analogous fact in the extension of the periodically moulted membrane of the peduncle, furnished with star-headed points of chitine, and in addition with minute calcareous beads (which, however, seem soon worn away), beyond the calcareous discs, by which this cirripede is attached in its cavity. We need not feel much surprise at points of chitine being hard enough to wear away shell, when we consider what work the jaws of insects, likewise formed of chitine, will effect.

With respect to the first commencement of the excavation, the pupa, owing to the position of its prehensile antennæ, fixes itself with its posterior end almost vertically upwards; and the young cirripede, after its metamorphosis, from the greater length of the ventral integuments formed round the eye-apodemes, must be thrown backwards into nearly the position represented in Pl. 22, fig. 12, b. I have not seen a young female at this early age, but I have traced the development of several males, and have found that the lower end of the peduncle, (i. e. what was the anterior end of the pupa), grows at quite a remarkable rate, so as very soon to form a great bag extending beyond the attached prehensile antennæ. Now if we suppose an analogous structure in the female or ordinary Alcippe, and the supposition is quite allowable, we shall almost immediately have the anterior or lower end of the young cirripede, just in advance of its antennæ, pressing against the surface of the shell of the mollusc; and if armed with triturating points, as we have every reason to believe it is, it would wear for itself a cavity. The horny disc on the ventral surface of this protuberant anterior end of the young animal will, we may assume, soon become cemented to the near side of the cavity just supposed to have been excavated. And the whole animal, by further slight changes in direction, namely, by working down more and more obliquely, will take, as shown at (c), its final position. As the whole surface of the animal, with the exception of the horny disc, is provided with triturating points, the animal, when once imbedded, can and does increase its cavity at both ends in length, in depth, and all round the edges of the horny disc, — in short, in every direction excepting directly over the horny disc. I believe, as already explained, that the young Alcippe, (b, diagram), first bores obliquely into the shell; and whatever amount of downward extension the horny disc attains before the young cirripede assumes its proper position, with its ventral surface upwards and parallel to the inner surface of the shell of the mollusc, that amount determines the thickness of the plate of shell hereafter to be left unabraded over the horny disc, as the latter continues to extend in circumference. This plate of shell over the horny disc is so thin, that, as mentioned at the commencement, the colour of the ovaria is seen through; and until I reflected on the following considerations, I was much surprised how the instinct of the animal could so neatly guide it not to grind too deeply, and yet to grind till only a very thin plate of shell was left over its horny disc: these considerations are, that whatever thickness was first given to this plate of shell, when the animal was very young and first assumed its ultimate position, that thickness would in most cases be always retained, owing to the flatness of the disc, and to the membrane armed with triturating points protruding very slightly beyond and above the horny disc, only just enough to wear away the surrounding shell to the thickness necessary to allow of the formation of each new zone of disc; as the disc itself is not armed, it subsequently has no power of wearing away the plate of shell above it. Thus the horny disc, besides giving support and attachment to the peduncle, is of this peculiar service that it seems to guide, (somewhat like the wood-part in a plane), the rasping powers of the lower extreme margin of the peduncle.

I may here observe that certain radiating and often punctured lines, mentioned and figured by Mr. Hancock, which help to render the thin plate of shell over the peduncle conspicuous (fig. 3), are formed by the burrows of an excessively minute annelid, the punctures being apparently the exit orifices: I imagine that these annelids find it difficult to commence their burrows on the smooth surface of the shell, and that they congregate at these particular spots and thence burrow in radiating lines, owing to their having taken advantage of the little cliff-like edges, at the narrow and disused ends of the fissures leading into the cavities occupied by the Alcippe, where alone they would not be disturbed by the action of the cirri, when first they commenced making their little burrows in the shell.

The fissure leading into the cavity is required to be broad at the posterior end, in order that the cirri may be there freely exserted out of the sack; and narrow in other parts, to prevent, as it would appear, anything injurious getting in between the animal’s body and the cavity in the shell of the mollusc. As the fissure is increased in length by attrition at the broad posterior end, which end during growth becomes broader and broader, the lower part of the fissure has to be narrowed, and this is effected in a very singular manner, namely, by advantage being taken of the strong tendency, which triturated shell with animal matter, has to set into a solid shelly mass, although constantly agitated. Mr. Hancock noticed this edging of hard shelly matter, and naturally thought it was a secretion. Lines of deposition (Pl. 22, fig. 4, b), parallel to the edges of the furrow can often be perceived in it: its thickness and extension vary much: I have seen it on one side alone of the orifice: it is, of course, never found at the broad end where the process of enlargement goes on. The peculiar worn surface with which it irregularly thins away downwards, on the sides of the cavity, made me (together with the apparent impossibility of such a secretion proceeding from an animal wholly invested by a chitine membrane) suspect it to be inorganic; and this view is certainly correct, for when a fragment is dissolved in acid, a considerable residuum is left of bits of membrane, rubbish, and, in one instance, even of the remnants of a foreign animal, apparently an annelid. We have here all the circumstances favorable for inorganic deposits of this nature, namely, finely triturated shell and chitine or animal matter, produced by the excavation of the chamber, sea-water, and movement.

I have given some remarkable cases in my volume on ‘Volcanic Islands,’ (), in which limestone, having almost the hardness and specific gravity of marble, has been thus deposited. Almost every coral-reef offers similar examples. The curious substance described by Mr. Horner and Sir David Brewster, (‘Philosoph. Transact.,’ 1836, ), which is formed during the manufactory of cloth, offers another example of the strong tendency which lime and animal matter have to unite. Lately, Dr. Horsford, in ‘Silliman’s North American Journal,’ Jan. 1853, has discussed the chemical theory in an analogous case on the coast of Florida; he attributes the aggregation to the formation of a hydrate of lime through the action of the animal matter. Mr. G. B. Sowerby, Junr., has described a case very analogous to that of Alcippe, (‘Proceedings of Zoolog. Soc., Mollusca,’ Pl. 5, fig. 4, , 1850), namely, that of Pholas calva, in which a tube is formed of inorganic calcareous matter, serving to narrow the entrance.

From the manner of growth of the animal, the fissure leading into the cavity in the shell becomes much longer than the orifice leading into the sack, and to prevent the body being unnecessarily exposed, the upward projection of the disc, already described, is formed under the narrow and disused end of the fissure; moreover, the two rims of the inorganic calcareous deposit sometimes here approach so closely, as almost or actually to touch each other; and between them, as remarked by Mr. Hancock, there is usually a little accumulation of grains of sand. This narrow end of the fissure is generally curled either to the right or left hand; and I can only account for this fact by supposing that, whilst the cirripede is young, and has not a large horny disc attached to the cavity, it cannot keep its body straight during the long-continued boring process.

The animal is attached by its horny disc to the thin shelly roof over the peduncle, and likewise to the under side of the narrow end of the fissure, but is elsewhere quite free. I carefully examined the disc in many specimens, but could not see any cement-ducts: I believe I saw layers of cement at the upper end of the disc, but it is not easy to discriminate between this substance and the yellowish, somewhat disintegrated, layers of the horny disc. The pupa certainly becomes attached by ordinary cement, so that the attachment in early life, at least, is normal. In some full-grown specimens, I found the lower parts of the horny disc attached, along the edges of the layers, to the roof of shell; and as I looked here in vain with the highest powers for cement-ducts, or for cement, it appears to me probable that the rough edges of these layers were united to the roof by a thin layer of the inorganic calcareous deposit. The animal, from its very protected situation, certainly requires to be less firmly cemented than other cirripedes; and even in Lithotrya, which is less deeply imbedded than Alcippe, the cementing apparatus was feebly developed. From the length of the pupal antennæ, cemented by their terminal segments, the position of the young cirripede (Pl. 22, fig. 12) can be changed to a considerable extent, like a ship swinging at her moorings, but in order to assume its final position, the animal must, I think, travel like Lithotrya, but to a much less extent, by a short succession of overlapping horny discs, — the old discs being partially deserted, each new one extending beyond the last-formed one: even in the case of the mature animal, we have seen that, under certain circumstances, it changes, to a certain extent, its position; portions of the old disc being deserted and attached to the roof of a deserted portion of the cavity.

Affinities. — In the preliminary remarks under the Family, I have discussed this subject almost sufficiently: I will here only remark, that the genus, though so abnormal, yet stands naturally between Ibla and Anelasma, having clear affinities, on the one side, through and beyond Anelasma to Alepas; and on the other side, beyond Ibla to Scalpellum, and so to Lithotrya. Moreover, it is very distinctly related to Cryptophialus in the succeeding Order.

MALE. Pl. 23.

On every specimen of the female Alcippe, which I carefully examined, I found some minute parasites (or epizoons) attached to the lateral edges of the upper part of the horny disc, and therefore lying within the narrow end of the fissure leading into the chamber excavated in the shell of the Buccinum. Although having had some experience in the very anomalous forms which male cirripedes assume, yet when I first casually inspected these parasites under a weak lens, from their transparency, their elongated and lobed body, including an internal folded up organ, I actually threw them away, thinking that they were probably Bryozoa. Subsequently, a more careful inspection immediately showed the cemented prehensile antennæ, and their cirripedial nature was demonstrated. I soon found specimens with the perfect still adherent exuviæ of the locomotive pupa, undistinguishable from the pupa already described as probably belonging to the female Alcippe. But as this latter fact, may perhaps be doubted, I must show that there is other evidence sufficient to prove that these cirripedial parasites are the males of the female Alcippe. Of the females, I inspected many specimens, and all certainly were without external male organs; and in the four or five specimens which I rigidly examined, there were no testes or vesiculæ seminales, the latter being in all hermaphrodite and male cirripedes so conspicuous. On the other hand, I examined at least thirty specimens of the parasite, and they were all exclusively males, for all had a probosciformed penis, and the greater number had their vesiculæ seminales filled with spermatozoa, and hence were ready to perform the act of impregnation, but undoubtedly they contained no ova. It would, then, be very strange, if these two cirripedes of opposite sexes, thus attached together, were not sexually related. Wonderfully different as the parasite is from the female Alcippe, yet, in one very important character it is related to Alcippe, and to no other member of the Family, namely, in the sack extending down to the extreme lower point of the peduncle; the male organs, I may add, occupying an analogous position with the peculiar position of the female organs in Alcippe. The lateral lobes of the peduncle in the parasite seem to represent the sides of the broad depressed peduncle in Alcippe; and in both the peduncle grows at its lower end — a very rare circumstance — observed only in two genera in this Family, namely, in Anelasma, and in a slight degree in Lithotrya. Besides these points of resemblance between Alcippe and its parasite, which are striking, considering their external utter dissemblance, the affinities of both point, judging from certain small characters, in the same direction, namely, towards Ibla and Alepas. Finally, then, I think, we may confidently admit that this parasite or epizoon is the male of the female Alcippe: indeed, considering the facts given in my former volume, on Ibla and Scalpellum, I have, perhaps, here discussed the question at unnecessary length.

The males are generally attached, as already stated, to the two hollowed out sides of the upward prolongation of the horny disc; they adhere by means of little patches of cement, proceeding from the terminal segments of their antennæ, to the overlapping edges of the few later-formed zones of the disc; hence, they lie protected, within the narrow end and a little under the edges of the fissure leading into the cavity in which the female is lodged. In some specimens, however, the males are attached rather lower down on the disc, and are not confined exclusively to its upper margin, so that they live fairly under the roof of shell which covers the main part of the disc: but they are never attached very low down, so as to lie far from the lower end of the orifice leading into the sack of the female. I have two or three times seen as many as three males on each side, but sometimes there is only one on each side, or none on one side. A large distorted specimen actually had twelve males, and two pupæ on the point of undergoing their final metamorphosis, all fourteen attached on one side, and all evidently must have been alive together! Another specimen had nearly the same number, a few on one side, and the rest on the other side.

 

The male immediately, after the exuviation of the pupal carapace, 25/1000th of an inch in length, is only 23/1000th of an inch long, but ultimately it becomes, chiefly from the growth of the lower end of the peduncle, nearly twice this length; for the largest specimen which I have seen, that figured, was 45/1000th of an inch long (i. e. under 1/20th of an inch), and 1/100th of an inch in breadth across the peduncle, beneath the lateral lobes. The whole external membrane of the animal (as well as the internal membrane of the sack), is very thin, quite structureless, and as transparent as glass; hence, even the spermatozoa, within the vesicula seminalis, can be seen from the outside. The whole structure of the animal is very simple. The ventral surface can be at once recognised by the attachment of the antennæ (fig. 19, a), and these organs mark the point which was the anterior end of the male, just at the period of its metamorphosis, and before the lower end of the peduncle had grown. These antennæ have already been fully described; they are conspicuous from being composed of membrane, rather thicker than that investing the body of the male, and which external membrane can be traced entering these organs, and appearing like cement-ducts; but within these tubular prolongations of the outer membrane, I could obscurely see the real cement-ducts.

The part answering to the capitulum is much flattened and elongated; it widens but little from the upper to the lower end, where it blends with the carinal or dorsal surface (the under surface in fig. 19) of the lobed peduncle. At the upper end there is a small orifice, and close to this, on the ventral or rostral side, there is a thin, apparently double projection (i, fig. 19) or flap of membrane, one flap lying exactly over the other. The whole length of this capitulum probably corresponds with that small portion of the capitulum in the female, between the upward prolongation of the horny disc and the lower end of the orifice; and the two broad flattened projections in the male, probably answer to the two sharp narrow points (a, fig. 1, Pl. 22) in the female. The peduncle has two lateral lobes (h, g, fig. 19), and, whilst young, what may be called a third and medial lobe, but this soon increases largely by growth, and forms the main part of the peduncle. The lateral lobes are intimately connected with the ventral surface; they tend to lie in a plane, at right angles to the compressed capitulum, but owing to the excessive thinness and flexibility of the whole external membrane, it is difficult to ascertain the relative position of the different parts. Moreover, owing to the pupa being so much flattened, these lobes are necessarily formed folded up; and, I believe, it depends on the position, with respect to surrounding objects, which the male ultimately holds, whether the lobes ever assume, their apparently normal position, in a plane at right angles to the sides of the pupa; owing, also, to the form of the pupa, the two lobes seem generally to be actually formed of unequal sizes, that formed in the dorsal region of the pupa being the largest. I believe that these lobes correspond with the lateral margins of the upper end of the peduncle of the female, which margins project laterally beyond the sides of the capitulum. The lower lobe, or end of the peduncle, is depressed in the same plane with the lobes; it is of variable length; when first formed it hardly extends beyond the basal articulation of the prehensile antennæ. Commonly it does not lie quite in a straight line of the capitulum; and I have seen specimens in which it stood at nearly right angles to the capitulum and to what was the ventral surface of the pupa; this irregularity in the relative position and sizes of the different parts of the peduncle, no doubt, to a considerable extent, depends on the form of surface to which the male becomes attached, just in the same way as we have seen that the peduncle of the female becomes altered in shape during the excavation of the chamber in which it is lodged.

I feel some difficulty on one point: in the pupa the single eye of the future male can be clearly distinguished, and it lies some way from the anterior end of the body; but in two males, which certainly had just moulted, and in which none of the internal organs were as yet developed, the eye lay close to the anterior end, directly over the basal articulation of the antennæ. I suspect this is somehow caused by the great change of form which supervenes, during the metamorphosis, at this anterior end of the body; the extremely compressed body of the pupa having to become depressed and lobed in the young male. I have given a figure of a young male, just as it appeared (Pl. 23, fig. 18), somewhat distorted from lying on a flat surface; c, being the eye.

The sack extends, in a very remarkable manner, down to the lower end of the peduncle, the whole inside of the animal being thus freely open to the water. In the upper part, the sack forms a mere narrow tube; it does not appear to have been formed in the same manner as in all other cirripedes, namely, surrounding the thorax and natatory legs of the pupa, but in an abnormal position, along the dorsal surface, above the sack and thorax of the pupa: a transparent line, where the new narrow sack is in process of formation, is the first indication of the coming metamorphosis. The sack in the capitulum of the male is not central, but lies near the dorsal surface; the ventral interspace, between the outside and the sack, is occupied by oblique fibres (l, fig. 19), which may be striæ-less muscles, but I suspect are ligamentous fibres, giving support to the whole projecting capitulum. These fibres enter a little way within the lobed peduncle; they are probably homologous with the strong muscles, which run from beneath the upper end of the horny disc of the female to the lower end of the orifice leading into the sack. Round the lobed peduncle, there are two bands (e, f) of thin muscular fasciæ, slightly oblique to each other, and attached at the ends to the outer membrane; they are evidently homologous with the external transverse muscles, which are best developed round the same part in the female. Some of these muscles present a singular chain-like appearance, from being strangled at intervals: they act probably in aiding the long probosciformed penis to protrude itself out of the sack. I could not detect any longitudinal muscles, and the lower part of the peduncle seems destitute of muscles of any kind.

I believe I saw in one specimen, most delicate transverse muscular fibres round the lower part of the elongated capitulum.

The internal structure of the animal is very simple. Within the lower end of the peduncle there is a dark purple eye (c), under the 1/1000th of an inch in diameter, a testis (d) and a (b) vesicula seminalis. These organs falsely appear as if suspended in the middle of the peduncle, but they are really attached, I believe within a separate partition, to the ventral surface, occupying the same position as the mass of ovarian cæca in the female. The eye lies on the line of junction between the testis and the vesicula seminalis, and on their ventral side. The testis is rounded, and consists of a mass of cells, on an average 1/5000th of an inch in diameter. The vesicula seminalis varies extremely in condition, being either a mere rather broad vessel, enlarged where it joins the testis, or a bag fully as large as the testis itself, and distended with spermatozoa, all arranged parallel to its longer axis. There was an evident relation between the size of the vesicula seminalis and that of the testis, the number of the cells in the latter decreasing as the mass of the spermatozoa increased: there was also an evident relation between the age of the male and the state of these organs; younger and more opaque individuals, having their testes of large size; and older specimens, with the lower end of the peduncle arrived at its full dimensions, having the vesicula distended. Some few old specimens had evidently discharged their spermatozoa. By dissection I more than once distinctly traced the vesicula seminalis entering the broad lower end of the penis. The membrane, forming the vesicula, is ringed, and I presume is, as in other cirripedes, contractile, so as to expel the spermatozoa. The probosciformed penis (m) is of extraordinary length: it is plainly ringed, or rather articulated, in this respect resembling that organ in Ibla and Alepas; it tapers gradually, and terminates (as usual) with a brush of fine bristles; it is furnished with delicate voluntary muscles, arising from the body round its basis, and extending no doubt up to the apex, but too fine to be traced all the way. Its broad lower end is attached in a slight depression, on the ventral side of the sack, a little above the point of attachment of the pupal antennæ. According to all analogy, the spot whence the penis springs must be considered as representing the thorax and abdomen; and the outer membrane of the penis is here, as on this view it should be, reflexed and is continuous with that lining the sack. Ordinarily the penis lies coiled up in complicated folds, appearing like a large intestinal worm, and fills the lobed part of the peduncle, which apparently serves for no other purpose than its reception. In one case in which I dissected out the penis, I found it in its contracted state; 41/1000th of an inch in length, equal to that of the entire capitulum and peduncle; in a specimen, in which the penis had been naturally exserted, the part which protruded (m) was by itself rather longer than the whole animal; and as this specimen had been placed in spirits of wine, the organ no doubt was contracted; hence I think it probable that the probosciformed penis, when fully stretched out, would equal twice the length of the entire animal.

There must be a nervous system; and there must likewise be a gland (homologous with the ovaria) for secreting the cement; but I could not distinguish parts so small. Certainly there is no mouth, or stomach, or thorax, or limbs of any kind, or abdomen.

It is obvious that these males must be very short-lived: they perform their masculine functions and then perish. We have seen, however, that after the act of metamorphosis they do grow a little, and I have reason to suspect that this is effected, as with other Cirripedes, by moulting. The growth must be absolutely dependent on the store of nutriment laid up within the pupa. The young male, immediately after the exuviation of the integuments, thorax, natatory legs, abdomen, and eyes of the pupa, consists of a pulpy cellular mass, without any internal organs as yet formed.

Judging from the different sizes of the females which included perfectly developed ova, I infer that they must breed more than once during their lives; and therefore, that successive sets of males, as in the genus Scalpellum, must become attached to them. I was not, however, able to discover the prehensile antennæ or other remains of the old males adherent to the females; a circumstance which I presume is accounted for by their attachment being weak. Considering the very small size of the male, it is not surprising that so many, — in one case fourteen, — are required to impregnate the numerous ova of a single female. How the males know the proper period when the ova, lying in a sheet at the very base of the sack of the female, are ready for impregnation, I cannot say, without it be that they perceive the moulting of the external membrane, close to the edge of which they are attached; for this moulting would indicate the period when the ovigerous lamella came to the surface of the sack, and the ova would then be soon ready for impregnation. From the position in which the males are attached, and from the extraordinary length of the probosciformed penis, capable of voluntary movements, I have no doubt the males can insert the tip of this organ within the lower edge of the orifice of the sack, and there discharge the spermatozoa, which, by their own movements, must pass down the sides of the sack of the female till they reach their proper destination. The position of the males, with respect to the female’s body, is almost exactly the same as that occupied by the complemental males of Scalpellum Peronii and villosum; the lower and narrow end of the fissure, worn in the gasteropod shell, here affording that protection to the males, which the edges of the opposed scuta afford to the complemental males of the above two species of Scalpellum. We cannot doubt that these latter males aid in the impregnation of the ova of the hermaphrodites, but they are not furnished with a very long penis, probably for the very reason that they are complemental males, and therefore not so absolutely necessary for the impregnation of the ova as are the males of Alcippe.

I have, in my former volume, expressed my astonishment at the extent to which abortion had been carried in the male Ibla; but it has been carried much further in the male Alcippe. In Ibla, the thorax is reduced to a mere flap, and only two pairs of cirri exist in a most useless and rudimentary state, but there is a well organised mouth, stomach, and anus. In the males of Scalpellum vulgare, ornatum, and rutilum there is no mouth or stomach, but there is a thorax with four pairs of minute, modified cirri, and a large abdominal lobe. Here, in the male Alcippe, all these negatives are united, we have no mouth, no stomach, no thorax, no cirri, no abdomen! The archetype crustacean consists of twenty-one segments; of these the seventeen anterior segments can be clearly made out in the archetype Cirripede: now, in the male Alcippe, the first three segments are largely developed, forming all that is externally visible, but the remaining fourteen segments are absolutely aborted, but in idea may be considered as forming the membranous depression whence the probosciformed penis springs; for this organ normally arises at the extremity of the seventeenth segment. To show the wonderful diversity of nature, even in the same sub-class, I may be permitted to remark, that whilst in Alcippe only the three anterior segments are developed, the fourteen succeeding segments being rudimentary, in Proteolepas (hereafter to be described) these fourteen segments are all largely developed, whilst the three anterior segments are quite aborted, being represented only by a thin envelope to the two threads by which this Cirripede is attached to the supporting object.

It may be worth stating, that in order to procure perfect specimens of the female and male Alcippe, pieces of the shell inhabited by them should be dissolved in weak acids.