Lepas pectinata. Spengler. Skrifter Naturhist. Selbskabet, 2, B. 2, H., 1793, Tab. X, fig. 2.
—— — muricata (var.) Poli. Test. Utriusque Scicil., vol. i, Pl. vi, figs. 23, 29, 1795.
Lepas anserifera. Poli. Test. Utriusque Scicil., vol. i, Pl. vi, figs. 25-27.
—— — sulcata. Montagu. Test. Brit., Pl. i, fig. 6, 1803.
Pentalasmis sulcata. Leach. Encyclop. Brit. Suppl., tom. iii, Pl. lvii, 1824.
—— —— —— — spirulæ (!) (var.) Leach. Tuckey’s Congo Expedit. Appendix, 1818.
—— —— —— — radula (var.) et sulcatus. Brown. Illust. of Conchology, Pl. li, figs. 3-6, 1844.
—— —— —— — inversus. Chenu. Illust. Conchy., Pl. i, fig. 14.
Anatifa sulcata. Quoy et Gaimard. Voyage de l’Astrolabe, Pl. xciii, figs. 18, 20.
I may add, that I have received many specimens incorrectly labelled A. striata, which is properly a synonym of L. anserifera.
L. valvis tenuibus, crassè sulcatis, sæpe pectinatis; scutorum cristâ prominente ab umbone ad apicem juxta marginem occludentem pertinente: furcæ carinalis cruribus inter angulos 135° et 180° divergentibus.
Valves thin, coarsely furrowed, often pectinated. Scuta with a prominent ridge extending, from the umbo to the apex, close to the occludent margin; fork of the carina with the prongs diverging at an angle of from 135° to 180°.
Filaments absent, or only one on each side.
Var. (Pl. I, fig. 3 a), upper part of the terga (bounded by the two occludent margins) produced and sharp; surface of all the valves often coarsely pectinated, and with the carina barbed.
Atlantic Ocean, from the North of Ireland to off Cape Horn; common, under the tropics; Mediterranean: attached to wood, cork, charcoal, sea-weed, a reed-like leaf, spirulæ, cuttle-fish bones, to a bottle together with L. anatifera; to a ship’s bottom, Belfast, (W. Thompson.) Often associated with L. fascicularis. Montagu states (‘Test. Brit.,’ ) that this species is sometimes attached to the fixed Gorgonia flabellum.
General Appearance. — The capitulum varies considerably in length compared to its breadth, caused chiefly by the greater or less production of the occludent portion of the terga; valves thin, brittle; the furrowed surface varies much in character, narrow and broad ridges often alternating; frequently each ridge (but more especially the ridge running from the umbo to the apex of each scutum, and sometimes that alone,) is covered with prominent, curled, flat, calcareous spines, giving the shell an appearance like that of many mollusca. Other specimens show no trace of these calcified projections. From the thinness of the valves and the depth of the furrows, the margins of the valves are sinuous. Scuta: the ridge running from the umbo to the apex is unusually prominent and curved; it runs very close to the occludent margin, so that, differently from in all the other species, only a very narrow space is left between this margin and the ridge. Internal teeth, under the umbones, either sharp and prominent, or mere knobs; sometimes that on the right side is much larger than that on the left; sometimes they are nearly equal; sometimes that on the left is scarcely distinguishable. Internal basal rim absent, or barely developed.
Terga: these valves have a conspicuous notch to receive the apex of the scuta; the two occludent margins either meet each other at a rectangle, or at a much smaller angle, causing the portion thus bounded to vary much in outline, area, and degree of prominence. This at first led me to think that the P. spirulæ of Leach, in which the point is very sharp and prominent, was a distinct species; but there are so many intermediate forms, that the idea must be given up. I may remark, that in all the species of Lepas, the upper part of the tergum seems particularly variable. The degree of acumination of the basal portion of the tergum also varies; the internal surface sometimes has small crests radiating from the umbo.
Carina, broad, within deeply concave; edges sinuous, externally sometimes strongly barbed; narrow above the fork, which latter is wider than the widest upper part of the valve; prongs sharp, thin, diverging at an angle of from 135° to 180°; the rim connecting the prongs not, or only slightly, reflexed.
Peduncle, narrow, shorter than the capitulum.
Filamentary Appendages, none, or only one, short, obtuse projection on each side, on the posterior face of the swelling under the first cirrus.
Mouth. — Mandibles, with the inferior point produced into a single pectinated tooth, rarely into two pectinated teeth; on one side of one specimen, there were only four instead of five teeth. Palpi very narrow. Maxillæ highly variable; they may be described as formed of five steps, of which the two lower ones are generally united into a single one, divided by a mere trace of a notch; or with the three lower steps blended into an irregular, projecting surface, and with even the fourth step indistinct. I have seen these two extreme forms on opposite sides of the mouth of the same individual, — on one side the maxillæ being regularly step-form, on the other the whole inferior part forming an almost straight edge, standing high up above the first notch or step which bears the two upper great spines.
Cirri. — First pair rather far removed from the second pair, with the longer ramus about three-fourths of the length of shorter ramus of second cirrus; spine-bearing surfaces, hardly at all protuberant; lateral marginal spines on the posterior cirri rather long; caudal appendages smooth, rounded, extremely minute: penis very spinose.
Size. — Capitulum in the largest specimen, six-tenths of an inch long; only a few arrive at this size.
Colours, after having been kept in spirits, — sack and cirri, especially first cirrus, clouded with pale purple; peduncle brownish; valves appear blueish in specimens not long preserved, but in specimens kept longer they become perfectly and delicately white.
General Remarks. — Under the head of L. anserifera, I have made some remarks on the diagnostic characters of this species. In the thinness of the valves, — form of the carina, with the rim connecting the prongs being not, or scarcely, reflexed, — and in the shortness and narrowness of the peduncle, there is some approach to L. australis, and thence to L. fascicularis. In the form of the maxillæ, — in one specimen having the mandible on one side bearing only four teeth, — and in the frequent absence of filamentary appendages, there is some approach to the genus Pæcilasma; but there is no such approach in the characters derived from the capitulum. We have seen that, as in so many other species of this genus, most of the parts are variable, and this is the case to a most unusual extent in the form of the maxillæ. Dr. Leach has attached eight specific names to the specimens preserved in the British Museum.