Molluscs are among the most familiar of all seashore invertebrates and also one of the most diverse. Many species are known for their shell, but in some species this is small or internal; in a few molluscs, the shell is absent altogether. Taken as a group, they occupy almost every conceivable niche in the coastal environment.
WHAT ARE MOLLUSCS?
Although molluscs are a diverse group, all have a body that comprises a head, a region called the visceral mass that contains the vital organs, and a muscular foot. The visceral mass is shrouded by tissue called the mantle; in a typical mollusc, the mantle margin secretes the shell. The mantle also encloses a cavity, connecting with the marine world, and inside which are located the gills as well as openings to the excretory and reproductive systems.
THE RANGE OF MOLLUSCS
Molluscs are divided in classification terms into several sub-groups. Those regularly found on the seashore include the following: chitons (class Polyplacophora); gastropod molluscs (class Gastropoda); bivalves – molluscs with paired shells (class Bivalvia); tusk shells (class Scaphopoda); and cuttlefish, squid and octopuses (class Cephalopoda). The gastropods are the largest class of molluscs and the group is separated further into a number of subdivisions that embrace everything from winkles and limpets to sea slugs and terrestrial snails.
Chitons – unusual and distinctive molluscs, oval in outline, whose shell comprises eight interlocking dorsal plates. The plates provide protection and a degree of flexibility; this allows the animal to clamp down onto irregular rock surfaces with the aid of its muscular foot.
Winkles, whelks, top shells and limpets (class Gastropoda, sub-class Prosobranchia) – a large and very varied mollusc group. The head bears eyes and tentacles, and the mouth has a rasping, tongue-like radula, used in feeding. Movement is achieved by a muscular foot, and the body is protected by a shell that is spiral in most prosobranchs, limpets being an exception. As with other gastropods, the latter half of the mantle cavity undergoes a process called torsion during larval development, whereby it twists through 180 degrees; facing forward, it provides a chamber into which the vulnerable head can be withdrawn.
Sea slugs and sea hares (class Gastropoda, sub-class Opisthobranchia) – not closely related to terrestrial slugs, these molluscs typically have no shell, or one that is greatly reduced. Their soft bodies are protected by noxious secretions and most species advertise the fact that they are distasteful with striking colours. In many sea slugs, gills are external and there are obvious tentacles at the head end. Movement is achieved by the muscular foot.
Terrestrial snails (class Gastropoda, subclass Pulmonata) – most familiar as land and freshwater snails (and slugs too), a few species are found on the seashore; fewer still have returned to the marine environment. In terrestrial species, the mantle cavity is filled with air and functions as a lung. The head has eyes and tentacles, and the mouth has a rasping radula for feeding. Movement is achieved by a muscular foot, and the body is protected by a shell that typically is spiral. As with other gastropods, torsion occurs during larval development.
Bivalves – in these molluscs, a hinged pair of shells protects the soft body. When the shell valves are open, siphons allow the flow of water through the mantle cavity and over the gills, where food particles are filtered out. The foot is often relatively large and muscular, while the head is absent. Many bivalves live buried, or part-buried, in sediment, while others attach themselves to rocks. There are also species that are free-living and a few can even swim by snapping their shells together to create propulsion.
Unusual molluscs with a cylindrical, tapering and slightly curved shell that is open at both ends. The head end projects slightly from the broader end of the cylinder, and bears clubbed tentacles that are used in feeding; in life, the head end is buried in sediment.
Cuttlefish, squid and octopuses – highly modified and distinctive molluscs, most of which are active predators. To facilitate this way of life, most have large eyes and sophisticated behaviour. In cephalopods, the mollusc foot has been modified to form long, muscular tentacles, armed with suckers for grasping prey.
Leptochiton asellus Length to 18mm
Rather plain chiton, found under stones on lower shore. ADULT is oval and yellowish. Shell plates show growth lines, keel and posterior ‘beak’; surface is finely granular in middle, coarser towards margins. Girdle is relatively narrow, with rectangular scales and marginal spines. STATUS Widespread and locally common on S and W coasts.
Lepidochitona cinerea Length to 25mm
upperside
underside
Our commonest chiton, usually found under stones on lower shore. ADULT has rather narrow girdle, covered in small granules and fringed with large, blunt spines. Shell plates are granular, with shallow keel and posterior ‘beak’; head plate has 9 or so notches. Colour variable, often greenish grey or yellowish, with bands on girdle. STATUS Widespread and locally common, least so on E England coast.
Callochiton septemvalvis Length to 3cm
Well-marked chiton, found under stones on lower shore. ADULT is oval and greenish or reddish, variably marbled with white. Shell plates show growth lines, keel and posterior ‘beak’; surface is finely granular in middle, coarser towards margins. Girdle is relatively broad, coated with dense, low spines and with marginal spines. STATUS Local and rather scarce, mainly on S and W coasts. SIMILAR SPECIES Tonicella rubra (length to 2cm) Colourful chiton, found under stones on lower shore. Adult has rather broad girdle, covered in oval granules and fringed with spines. Shell plates are smooth. Widespread and locally common.
Acanthochitona crinita Length to 3cm
Distinctive oval chiton. Found on rocks on lower shore. ADULT has rather broad girdle with 18 tufts of bristles and fringe of spines. Shell plates have unevenly scattered, relatively large pear-shaped granules. Colour variable, often marbled brown, reddish or yellow. STATUS Widespread and locally common. SIMILAR SPECIES A. fascicularis (length to 6cm) has shell plates coated with fine, even granulation. Colour is variable but sometimes has dorsal row of pale V markings; locally common only in S and SW.
Tusk Shell Antalis entalis Length to 4cm
Tusk-like. Lives buried, head down, in offshore sand; sometimes washed up on beaches. SHELL is white, cylindrical, curved and tapering (broadest at head end). Open both ends; posterior end has circular aperture. STATUS Widespread and locally common, least so in the S. SIMILAR SPECIES A. vulgare is larger (length to 6cm), with oval posterior aperture; in the SW only.
Slit Limpet Emarginula fissura Length to 1cm
Cap-shaped mollusc, found on rocks on lower shore. Feeds on sponges. SHELL is buffish yellow and conical, with swept-back profile when seen side on. Has distinct slit in anterior margin. STATUS Widespread and locally common.
Common Keyhole Limpet Diodora graeca Length to 7mm
Distinctive mollusc, found on rocks on lower shore. Feeds on sponges. SHELL is flattened-conical in profile; viewed from above, outline is oval and note narrowly oval apical hole. STATUS Locally common only in the N and W.
Green Ormer Haliotis tuberculata Length to 9cm
Unmistakable ear-shaped mollusc, found on rocky shore at low water. Feeds on small red seaweeds. SHELL is oval with a small spiral and marginal row of holes through which mantle protrudes. Outer surface is rough and marbled green and brown; inner surface has mother-of-pearl lining. STATUS Restricted to Channel Islands but locally common there.
Common Limpet Patella vulgata Length to 6cm
Common Limpet, underside, showing foot
Familiar mollusc and our commonest limpet. Found on rocks between mid- and low water. SHELL is conical with radiating ridges; shells on higher shore have steeper cone than those lower down. Inside of shell is greenish grey and sole of foot is orange. STATUS Widespread and locally abundant.
Black-footed Limpet Patella depressa Length to 3cm
Black-footed Limpet, underside, showing foot
Black-footed Limpet, inside of shell
Well-marked limpet, found on exposed rocky sites on lower shore. SHELL is flattened-conical with radiating ridges. Inner surface is yellowish with marginal dark rays; sole of foot is black STATUS Restricted to the SW.
China Limpet Patella ulyssiponensis Length to 5cm
China Limpet, underside, showing foot
Distinctive limpet, found on exposed rocky sites on lower shore. SHELL is flattened-conical with radiating ridges. Inner surface is porcelain-white, tinged yellow towards centre; sole of foot is orange. STATUS Commonest in the W, absent from the SE.
Common Tortoiseshell Limpet Tectura testudinalis Length to 3cm
Beautifully patterned limpet, found on lower shore on rocks encrusted with small red seaweeds. SHELL is flattened-conical and rather smooth; typically whitish, marbled with brown and grey. STATUS A mainly N species, absent from the SE.
White Tortoiseshell Limpet Tectura virginea Length to 1cm
Delicate-looking limpet, found on lower shore on rocks encrusted with small red seaweeds. SHELL is flattened-conical and smooth; typically whitish or pale pinkish, with radiating, subtly darker rays (these can be absent). STATUS Widespread and locally common.
Slipper Limpet Crepidula fornicata Length to 5cm
Slipper Limpet, mass of animals
Familiar mollusc, found on muddy and gravelly shores, often washed up alive. Arching stacks of several animals are common. SHELL is oval and cap-shaped, with small, shallow spire; outer surface is pinkish brown. STATUS Accidentally introduced from North America, now locally abundant in the S.
Blue-rayed Limpet Helcion pellucidum Length to 15mm
Blue-rayed Limpet, living animal
Blue-rayed Limpet, worn shell
Distinctive limpet, typically found on fronds and stipes of Laminaria seaweeds. SHELL is cap-shaped and domed, with eccentric apex; surface is smooth, translucent and chestnut-brown with radiating lines of blue spots. Older animals may have worn chalky shells with a ‘ledged’ profile. STATUS Widespread and locally common.
Grooved Top Shell Jujubinus striatus Height to 10mm
Attractive mollusc, found at low water among eelgrasses and Codium seaweeds. SHELL is conical and flat-sided (not ‘stepped’), with 8–10 whorls and 8–10 shallow ridges per whorl. Usually whitish with dark brown markings. STATUS Mainly in the SW.
Thick Top Shell Osilinus lineatus Height to 30mm
Robust, heavy-shelled mollusc, found on sheltered rocks on lower shore. SHELL is rounded-conical in outline with 5–6 whorls; aperture has obvious tooth. Typically rufous brown with darker zigzag markings; worn areas reveal mother-of-pearl colours. STATUS Locally common, mainly in the W and SW.
Painted Top Shell Calliostoma zizyphinum Height to 30mm
Painted Top Shell, living animal
Painted Top Shell
Elegant shell, found on sheltered rocky shores; usually sub-littoral, sometimes at low-water mark. SHELL is conical with pointed apex and 10–12 subtly ribbed whorls. Usually marbled pinkish brown and white. STATUS Widespread but rather local.
Grey Top Shell Gibbula cineraria Height to 15mm
Well-marked shell, familiar on strandline; in life, found on rocky shores at extreme low water and in pools. SHELL is rounded-conical with 5–6 finely ridged whorls. Usually buffish grey with narrow reddish-brown bands. STATUS Widespread and locally common.
Flat Top Shell Gibbula umbilicalis Height to 20mm
Similar to Grey Top Shell but flatter, and with more convex profile. Found on rocky shores, from mid- to low water into sub-littoral zone. SHELL is bluntly conical, the 5–6 whorls with fewer ridges than Grey Top Shell. Usually greenish with widely spaced reddish-purple bands. STATUS Widespread in the W; absent from much of the E coast.
Turban Top Shell Gibbula magus Height to 30mm
Stout, robust shell. Found on lower shore on rocky and mixed substrates. SHELL is rounded overall with 8 ridged whorls; shells are pinkish brown, patchily suffused with orange, and typically worn and damaged. STATUS Locally common in the S and NW; absent from most of the E coast.
Pheasant Shell Tricolia pullus Height to 8mm
Colourful and beautifully patterned shell. Associated with red seaweeds on sheltered shores. SHELL is ovoid with up to 6 whorls, yellowish with intricate red patterning. STATUS Locally common in the S and W; absent from the E coast.
Least Chink Shell Lacuna parva Height to 4mm
Minute shell. Found on Fucus seaweeds on middle and lower shore. SHELL has globular shell with low spire. Head has long, slender tentacles. STATUS Widespread and locally common, except in the SE.
Banded Chink Shell Lacuna vincta Height to 10mm
Well-marked shell. Found on seaweeds, notably Serrated Wrack, and eelgrasses. SHELL is ovoid with a pointed spire and 5 whorls; yellowish buff with brown spiral bands. STATUS Widespread and locally common, although absent from much of the SE.
Cingula trifasciata
Rissoa parva, living animal
Small, well-marked shell. Often abundant among red seaweeds on sheltered rocky shores. SHELL is ovoid with a pointed spire, sometimes with low ridges on the whorls; usually buffish white with dark bands. Aperture can be closed with an operculum. STATUS Widespread and locally common, except in the E. NOTE There are several very similar Rissoa species. SIMILAR SPECIES Cingula trifasciata (height to 4mm) has tiny shell. Found on rocky shores, under seaweed and rocks at low tide. Shell is rather ovoid with a conical spire. Usually buffish with dark spiral stripes (3 on largest whorl). Widespread and commonest in the W and N.
Laver Spire Shell Hydrobia ulvae Height to 6mm
Hydrobia ventrosa
Hydrobia neglecta
New Zealand Mudsnail
Assorted Hydrobia species
Small, ecologically important species. Found mainly in estuaries. SHELL is a conical spire with almost straight-sided whorls. Typically grey-brown but often coated with mud. Head has pale tentacles with dark sub-terminal band. STATUS Widespread and common on suitable coasts. SIMILAR SPECIES H. ventrosa has rounded whorls and tentacles without dark band. H. neglecta has rounded whorls and tentacles with dark marks close to tip. New Zealand Mudsnail Potamopyrgus antipodarum has slightly rounded whorls and tentacles with pale central line.
Black-lined Periwinkle Littorina nigrolineata Height to 30cm
Distinctive shell; found on rocky shores, typically amongst Ascophyllum and Fucus seaweeds. SHELL is rounded with a short spire and 5 or 6 whorls; yellowish with dark spiral lines. STATUS Locally common, mainly in W Britain.
Small Periwinkle Littorina neritoides Height to 8mm
Tiny shell, easy overlooked when lodged in crevices, empty barnacle cases, etc. Found on rocky shores, usually above mid-tide level. SHELL is ovoid with a pointed spire; usually dark grey. STATUS Widespread and locally common, except in the E.
Common Periwinkle Littorina littorea Height to 30mm
Familiar shell; found on sheltered rocky shores, across intertidal zone. SHELL is ovoid with a pointed spire and rough, sculptured whorls; usually grey-brown, appearing blackish when damp and out of water. STATUS Widespread and locally very common, least so on the E coast.
Flat Periwinkle Littorina obtusata Height to 10mm
Flat Periwinkle, colour forms
Distinctive shell. Found on sheltered rocky shores; associated with brown seaweeds, notably Ascophyllum and Bladder Wrack. SHELL is ovoid, with a low, flat spire and rounded aperture; often yellow, but orange, grey-brown and even chequered shells occur in different habitats. STATUS Widespread and locally very common, least so on the E coast.
Littorina mariae Height to 10mm
Very similar to Flat Periwinkle. Found on rocky shores, typically on Serrated Wrack. SHELL is globular, with a low, flat spire and very large, oval aperture. STATUS Widespread and locally common, mainly in the W and SW.
Rough Periwinkle Littorina saxatilis Height to 17mm
Littorina rudis
Solid shell; found on upper shore, usually among seaweeds, in habitats ranging from rocky shores to estuaries. SHELL is globular with a pointed spire and ridged whorls; colour is variable but often orange or brown. STATUS Widespread and generally common. SIMILAR SPECIES Several very similar species exist: L. rudis is found on Channel Wrack; L. tenebrosa has a thinner, less sculptured and more rounded shell and occurs in estuaries; L. arcana is found on upper zones of exposed rocky shores, among Verrucaria lichens.
Littorina neglecta Height to 5mm
Tiny, easily overlooked shell. Usually found on exposed rocky shores, in crevices and empty barnacle shells. SHELL is globular and thin, with a short, blunt spire; usually yellowish brown with a dark spiral band or dark patterns. STATUS Locally common, mainly in the W and N.
Auger Shell Turritella communis Height to 55mm
Almost unmistakable. Sub-littoral on sandy shores; in life, buries itself, but empty shells are often washed up. SHELL is an elongate and sharply pointed spire with sculptured whorls. STATUS Widespread and locally common, although absent from the SE.
Common Wentletrap Epitonium clathrus Height to 40mm
Beautiful, distinctive shell. Sub-littoral on soft substrates, feeding on sea anemones; empty shells sometimes washed up. SHELL is a tall spire with up to 15 strongly ribbed whorls. Buffish white, sometimes with brown spiral bands. STATUS Widespread but very local.
Needle Whelk Bittium reticulatum Height to 10mm
Small shell, easily overlooked. Found on muddy sand in sheltered spots, often amongst eelgrasses. Empty shells are best found by sieving. SHELL is a slender spire with 12–15 whorls, evenly sculptured with criss-crossing spiral and longitudinal ridges. STATUS Widespread and fairly common on the S coast; more local in the W and absent from the E.
Cerithiopsis tubercularis Length to 7mm
Sculptured shell with a sinistral spiral. Found on sponges (on which it feeds), often with coralline seaweeds, under rocks on lower shore. SHELL is slender, tapering towards conical tip. Whorls bear spiral rows of tubercles. STATUS Commonest along S England coast and W Wales.
Violet Snail Janthina janthina Width to 35mm
Unmistakable mollusc. Pelagic and oceanic but sometimes blown onshore during prolonged gales. Empty shell is fragile and breaks easily. SHELL is pale violet and almost spherical, with a large outer whorl and aperture. In life, dark violet-brown animal can be seen attached to ‘float’ of mucus-trapped bubbles. STATUS Occasionally washed up on W coast beaches in summer, typically when large numbers of By-the-wind-sailor (on which it feeds;) are also stranded.
Pelican’s Foot Aporrhais pespelecani Height to 40mm
Elegant and unmistakable shell. Sub-littoral, ploughing through surface of muddy sand. Empty shells often washed up. SHELL comprises a spire with ridged whorls and outer lip of aperture extending as projecting points. STATUS Widespread and locally common in the S and W; virtually absent from the E coast.
Hungarian Cap Shell Capulus ungaricus Width to 25mm
Distinctive shell. In life, clamps onto other mollusc shells, notably those of scallops and Horse-mussels. SHELL is broad, flattened and ridged, with an apical spire; usually yellowish brown. STATUS Local, mainly in the W.
Chinaman’s Hat Calyptraea chinensis Width to 15mm
Flattened, limpet-like shell. Found on lower shore, usually on stones among soft substrates. SHELL is a low yellowish cone; plate-like partition is seen inside shell. STATUS Local, on the S coast and SW Wales.
Spotted Cowrie Trivia monacha Length to 12mm
Spotted Cowrie, juvenile
Spotted Cowrie, living animal
Distinctive shell. Found on rocky shores, feeding on ascidians, notably Star Ascidian and Botrylloides leachii. SHELL is flattened-ovoid and glossy, with a ribbed surface and slit-like aperture; pinkish buff with 3 dark spots. In life, mantle wraps around most of shell. Juveniles have a short spire. STATUS Widespread and locally common; commonest in the S, and scarce or absent from the E coast.
Arctic Cowrie Trivia arctica Length to 10mm
Similar to Spotted Cowrie but shell is unspotted. Found on lower shore on rocky coasts; feeds on ascidians. SHELL is flattened-ovoid, glossy and whitish. In life, mantle wraps around most of shell. STATUS Widespread and locally common except on E coast.
Necklace Shell Euspira catena Height to 30mm
Attractive and distinctive shell. In life, animal ploughs through sand searching for bivalve mollusc prey. Drills neat hole in shell; empty prey shells (and those of Necklace Shell) are found washed up on suitable shores. SHELL is orange-brown, shiny and rather spherical, with large final whorl and aperture. STATUS Locally common in the S and on the Welsh coast; rather scarce elsewhere.
European Sting Winkle Ocenebra erinacea Length to 50mm
Distinctive sculptured shell. Predator of bivalve molluscs and barnacles found on lower shore, on rocky and mixed coasts. SHELL has conical spire and broad aperture, with whorls bearing ribs and projections. STATUS Widespread and locally common in S and SW England and Wales; scarce elsewhere.
Common Whelk Buccinum undatum Length to 10cm
Large, familiar whelk of rocky and mixed shores; feeds on worms and bivalve molluscs. SHELL has broadly oval aperture and conical spire, with ridged whorls and slightly ‘stepped’ outline. Typically pale brown. STATUS Widespread and locally common. NOTE Lays yellowish egg masses under rocks; these are often washed up.
Red Whelk Neptunea antiqua Length to 15cm
Recalls Common Whelk, but smoothly rounded whorls give it a ‘smoother’ outline. Found on rocky and mixed shores; feeds on carrion and a predator of marine worms. SHELL has narrowly oval aperture, flushed orange-red inside, and rounded whorls with fine spiral ridges. Typically grey-buff. STATUS Locally common, mainly in the N and NW.
Distinctive narrow shell. Usually sub-littoral on sand and mud, but shells are washed up. SHELL has narrowly oval aperture and slender, conical spire, sharply pointed at tip. Whorls are finely ridged but outline is flat-sided. Usually buffish white; aperture mouth is pale. STATUS Mainly in the N.
Dog Whelk Nucella lapillus Length to 40mm
Dog Whelk, adult with eggs
Familiar seashore mollusc. Found on rocky shores, especially sheltered sites, and feeds on barnacles and mussels. SHELL is oval in outline with spirally ridged whorls; spire is conical and pointed, aperture is oval with thickened, ribbed outer lip. Colour influenced by food, but often greyish or yellowish, sometimes with dark spiral bands. STATUS Widespread and locally very common. NOTE Clusters of yellowish egg capsules (like large wheat grains) are laid on rocks in spring.
Thick-lipped Dog Whelk Hinia incrassata Length to 12mm
Robust shell, found on rocky and mixed shores, often under boulders and in pools at low tide. SHELL is brown and ovoid, with ribbed and spirally grooved whorls; aperture is smallish and rounded with thick, toothed outer lip. STATUS Widespread and locally common, but scarce on the E England coast.
Netted Dog Whelk Hinia reticulata Length to 30mm
Robust, compact shell. Usually found on sand and muddy substrates among rocks. SHELL is rather pear-shaped in outline, with ribbed and spirally grooved whorls; aperture is elongate-oval with fine-toothed inner margin to outer lip. STATUS Widespread and locally common only on S and W coasts. SIMILAR SPECIES Small Dog Whelk H. pygmaea (length to 14mm) is less ‘netted’ in appearance and has wider aperture. Sub-littoral on sand; sometimes washed up. NW and SW Britain; absent from Irish and North seas.
Sea Lemon Archidoris pseudoargus Length to 10cm
Sea Lemon, eggs
Our most familiar sea slug. Found on rocky shores, often under rocks at low tide. Feeds on encrusting sponges. ADULT has warty texture, with lamellate rhinophores at head end, and ring of frilly gills at tail end. Colour is variable but typically blotchy yellow and brown. STATUS Widespread and locally common only on S and W coasts.
Geitodoris planata Length to 60mm
Can be confused with Sea Lemon. Found on rocky shores at low tide and in pools. ADULT is brownish yellow (darker than Sea Lemon), with 5–6 star-shaped patches (acid glands) on each side of mantle. In addition to rhinophores, has oral tentacles (lacking in Sea Lemon). STATUS Local, SW Britain only.
Onchidoris bilamellata Length to 40mm
Well-marked sea slug. Found on rocky shores; feeds on barnacles. ADULT is blotched brown and white; mantle is covered in relatively long, blunt tubercles. Has lamellate rhinophores and up to 29 rather short gills arranged in a wide circle. STATUS Widespread but local; mainly in the S and NW.
Goniodoris nodosa Length to 25mm
Distinctive sea slug, found on sheltered rocky shores at low water and in pools. Feeds on encrusting bryozoans and ascidians. ADULT has a translucent white mantle, studded with white spots, sometimes with pinkish body showing through. Has rhinophores, oral tentacles and up to 13 tentacles. STATUS Widespread but local; absent from much of the E England coast.
Acanthodoris pilosa Length to 30mm
Acanthodoris pilosa, mating pair and eggs
Distinctive sea slug. Found at low water on rocky shores where bryozoan prey are common; easiest to find in spring. ADULT is usually white, mantle with rather long, pointed tubercles. Has stalked lamellate rhinophores and up to 9 feathery gills. STATUS Widespread, commonest in the S and W, scarce on the E coast.
Jorunna tomentosa Length to 50mm
Unobtrusive sea slug. Feeds on encrusting sponges on lower rocky shore and in sub-littoral zone. ADULT is whitish or yellowish (sometimes with dark paired dorsal spots), with a woolly or velvety texture, a ring of pale retractile gills and brownish lamellate rhinophores. STATUS Widespread and locally common.
Greilada elegans Length to 30mm
Colourful and unmistakable sea slug. Found on rocky coasts; usually sub-littoral but sometimes in pools. ADULT is orange with blue spots. Has lamellate rhinophores, short oral papillae and up to 7 dorsal gills. STATUS Local and scarce; restricted to the SW.
Attractive little sea slug. Found on sheltered rocky shores; feeds on ascidians. ADULT is translucent white (internal organs can sometimes be discerned), with orange-tipped projections and rhinophores, and dorsal gills surrounded by projections. STATUS Widespread but local, mainly in the S and NW.
Orange-clubbed Sea Slug Limacia clavigera Length to 15mm
Small, colourful sea slug. Found on rocky shores at low water and in pools. Feeds on bryozoans. ADULT is white with orange-yellow spots, marginal projections and lamellate rhinophores. STATUS Locally common on SW and W coasts; absent from much of the E coast.
Polycera quadrilineata Length to 35mm
Attractive sea slug. Found near its food (encrusting bryozoans) in pools and at low water on sheltered rocky shores. ADULT is translucent white, with rows of orange-yellow patches and lines on body. Head has 4 terminal projections; these and rhinophores are tipped orange-yellow. STATUS Locally common, especially in the W.
Sea Hare Aplysia punctata Length to 70mm
Sea Hare, young animal
Sea Hare, eggs
Familiar sea slug. Found in a wide range of habitats; probably commonest on sheltered rocky shores. Feeds on seaweeds. ADULT is usually reddish (sometimes brown or green), marked with numerous white spots. Head has long rhinophores and oral tentacles, giving it a fancifully horse- or hare-like appearance. Note wing-like flaps along body length. STATUS Widespread and locally common in the W and SW; virtually absent from the E coast.
Colourful and distinctive sea slug, but well camouflaged among green seaweeds, notably Velvet Horn, on which it feeds. Found on sheltered rocky shores. ADULT is usually green with bright blue and red spots. Has smooth paired rhinophores and wing-like parapodial flaps along most of body. STATUS Widespread and locally common on S and NW coasts; scarce or absent elsewhere.
Facelina auriculata Length to 35mm
Slender sea slug. Feeds mainly on Tubularia indivisa; lower-shore pools and sub-littoral zone. ADULT has pinkish-flushed pale body and ringed brown rhinophores. Body has whorls of white-tipped purple cerata; oral tentacles are long. STATUS Widespread but local.
Facelina bostoniensis Length to 50mm
Facelina bostoniensis, disturbed animal
Relatively broad sea slug. Feeds on Tubularia hydroids, on lower shore and in sub-littoral zone. ADULT has translucent white body, tinged pink, and white-tipped ringed rhinophores. Body has overlapping, white-tipped brown cerata. Curls into ball when agitated. STATUS Widespread and locally common, mainly from SW England to NW Scotland.
Flabellina pedata Length to 45mm
Colourful sea slug. Feeds on hydroids; lower shore and sub-littoral zone. ADULT has purple body and pinkish-red cerata; tentacles, ribbed rhinophores and cerata are white-tipped. STATUS Widespread, commonest in the S and W.
Catriona gymnota Length to 20mm
Elegant sea slug. Feeds on Tubularia hydroids; lower-shore pools and sub-littoral zone. ADULT has whitish body, oral tentacles and rhinophores. Cerata are swollen, orange and white-tipped. STATUS Local, mainly in the SW.
Grey Sea Slug Aeolidia papillosa Length to 10cm
Impressive and distinctive sea slug. Found on rocky shores where sea anemones (its food) are common. ADULT is greyish white or brownish white, with long, soft projections arranged in rows down sides, leaving dorsal surface bare. Head has smooth rhinophores and oral tentacles. STATUS Locally common on S and W coasts; scarce or absent elsewhere.
Aeolidiella alderi Length to 30mm
Recalls Grey Sea Slug but smaller. Found on rocky and mixed shores, usually in vicinity of prey (sea anemones, notably Daisy Anemone), and under stones at low tide. ADULT is mostly pale yellow, flushed orange towards head. Has soft projections in rows down sides, those at head end whitish. STATUS Local, mainly in the S and W.
Well-marked sea slug found on sheltered rocky shores. ADULT is olive-green with a network of pale patches and tubercles. Has lamellate rhinophores and 5 frilly gills. STATUS Widespread but rather scarce.
Small, compact sea slug, found on sheltered rocky shores. Feeds on sponges. ADULT is translucent creamy white, studded with paler tubercles and yellow spots near margins, and with yellowish mantle fringe. Has yellow-tipped lamellate rhinophores and, usually, 5 frilly gills. STATUS Widespread in the N and NW, scarce in the SW and absent elsewhere.
Celtic Sea Slug Onchidella celtica Length to 15mm
Unusual mollusc, more closely related to land snails than true sea slugs. Found on rocks in the splash zone, often hiding among barnacles or in rock crevices. Active in damp weather. ADULT has blackish-grey dorsal surface, covered in knobbly tubercles. Tentacles visible when active. STATUS Local, mostly in Cornwall and N Devon.
Berthella plumula Length to 40mm
Colourful sea slug with internal shell; easily overlooked out of water as it contracts to a flattened blob. Found on rocky shores, feeding on Star Ascidian and other ascidians. ADULT has subtle reticulate pattern. Rhinophores and oral tentacles are inrolled. STATUS Widespread on SW and W coasts only.
Lamellaria perspicua Length to 25mm
Lamellaria perspicua, orange form
Lamellaria perspicua, underside
Unusual mollusc with internal shell, recalling but unrelated to true sea slugs. Found on sheltered rocky shores; feeds on ascidians. ADULT is unevenly domed, with subtle reticulate pattern; colour variable, often marbled greyish white, but sometimes white or orange. Mantle forms tubular opening at front. STATUS Widespread but local on S and W coasts.
Velvet Shell Velutina velutina Width to 20mm
Unusual mollusc. Found on stony and mixed substrates; usually sub-littoral but empty shell is sometimes washed up. SHELL is ear- or cap-shaped with extremely large outer whorl. Outer coating (periostracum) is brown and slightly furry. STATUS Widespread but local.
Runcina coronata Length to 6mm
Small sea slug with internal shell. Found on sheltered rocky shores, often on Velvet Horn, on which it feeds. Easily overlooked. ADULT has a dark brown mantle with numerous small, pale spots and orange margin. Head has yellow margin and white-spotted ‘collar’. Yellowish foot is visible posteriorly. STATUS Widespread but local, mainly in the SW and W.
Lobe Shell Philine aperta Length to 60mm
Strange-looking sea slug with an internal shell. Found on lower zones of sandy beaches; feeds on polychaete worms and bivalve molluscs. ADULT is creamy white and 4-lobed. STATUS Widespread and locally common on S and W coasts.
Haminoea navicula Length to 60mm
Unusual shelled sea slug. Found in saline lagoons and sheltered eelgrass beds in estuaries. Empty shells are easier to find than living animals. ADULT has spotted brown body; mantle and lateral flaps envelop shell. Shell is fragile and ovoid; aperture runs entire length of shell; whorls are not visible when viewed end on. STATUS Local, mainly restricted to Hampshire and Dorset.
Akera bullata, living animal
Unusual shelled sea slug. Found in saline lagoons and sheltered eelgrass beds. ADULT has brown body with pale spots. Head has shield-like cover and lateral flaps are occasionally used for swimming. In life, mantle and flaps partly envelop shell. Shell is ovoid; aperture runs length of shell; whorls are visible when viewed end on. STATUS Very local, with a scattered distribution, mostly in Hampshire and Dorset, and NW coast.
Acteon tornatilis Length to 25mm
Acteon tornatilis, living animal
Unusual sea slug. Has shell into which animal can withdraw. Found on sandy shores, burrowing and feeding on marine worms, including Sand Mason. Empty shells often washed up. ADULT has an ovoid shell, pink with pale spiral bands. In life, mantle flaps are broad. STATUS Widespread, mainly on W coasts; perhaps commonest in Wales.
Ark-shell Arca tetragona Length to 45mm
Unmistakable bivalve, attached by byssus threads to rocks. On lower shore and sub-littoral zone. SHELL is rectangular in outline, with angular sides and radiating ribs. STATUS Mainly in the N, locally common only in Hebrides and Orkney.
Dog Cockle Glycymeris glycymeris Width to 60mm
Beautifully patterned bivalve. Sub-littoral in sand; empty shells often washed up. SHELL is circular in outline, usually yellowish buff with concentric reddish-brown zigzag lines. STATUS Locally common in the S and W; absent from much of the E.
Common Mussel Mytilus edulis Width to 60mm
Familiar bivalve. Lives attached to rocks and other hard substrates in areas of fast-flowing water on lower shore, attached by byssus threads. SHELL is oval to fan-shaped, pointed at one end. Typically tinged bluish purple but can look blackish. STATUS Widespread and locally common. SIMILAR SPECIES Nucula nucleus (length to 10mm) is a small bivalve, found in gravel and coarse sand. Mostly sub-littoral but shells are washed up. Shell is brown with concentric growth ridges and bands; outline is broadly triangular with 1 curved edge. Commonest off the S England coast and Wales.
Horse-mussel Modiolus modiolus Width to 100mm
Similar to Common Mussel but larger. Mostly sub-littoral but shells often washed up. SHELL is oval to fan-shaped in outline; umbo is rounded. Typically rusty brown. STATUS Widespread and locally common.
Bearded Mussel Modiolus barbatus Width to 60mm
Distinctive bivalve. Mainly sub-littoral but empty shells sometimes washed up. SHELL is angular-oval in outline, pointed at 1 end. Typically brown, broader part of shell with stout bristles. STATUS Local, mainly on S and W coasts, north to N Wales. SIMILAR SPECIES Bean Mussel Modiolula phaseolina (width to 20mm) is a tiny, distinctive mussel found lodged in kelp holdfasts and under rocks on lower shore. Oval brown shell has spiny outgrowths on periostracum. Local, mainly in the W and N.
Zebra Mussel Dreissena polymorpha Width to 30mm
Unwelcome introduction from Russia. Mainly in fresh water but also in upper tidal reaches of a few large rivers, including the Exe and Thames. Attaches to stones and other mussel species by byssus threads. SHELL has fan-shaped outline; typically buffish with concentric brown zigzag lines. STATUS Widespread in England; local in Wales and Scotland.
Marbled Crenella Modiolarca tumida Width to 20mm
Small, well-marked bivalve. Lives in kelp holdfasts and embedded in large tunicates. SHELL is oval and ribbed; usually yellowish green, marbled with reddish brown. STATUS Widespread and locally common, except on the E coast.
Green Crenella Musculus discors Width to 12mm
Tiny bivalve with unusual habits: moves using its muscular foot, with long siphon protruding. Found on lower shore on rocky coasts. SHELL is angular-oval, often white but sometimes tinged greenish. STATUS Widespread but almost absent from the E.
Musculus costulatus Width to 15mm
Well-marked bivalve. Lives attached to rocks and algal holdfasts by byssal threads, but capable of reorientation using muscular foot. SHELL has ribbed valves, yellowish overall but with bold reddish-brown markings, many of which are V-shaped. STATUS Widespread but local, mainly in the SW.
Saddle Oyster Anomia ephippium Width to 50mm
Heteranomia squamula
Heteranomia squamula
Unusual bivalve. Attaches to rocks and encrusting weeds on lower shore of sheltered rocky coasts. SHELL is rounded in outline, with 2 dissimilar valves: lower (right) valve is flat with oval hole at base and is attached to substrate; upper (left) valve is domed. Has 3 muscle scars on inner surface of upper valve. STATUS Widespread and locally common, least so on the E coast. SIMILAR SPECIES Heteranomia squamula (width to 15mm) is more delicate, with 2 muscle scars on inner surface of upper valve.
Great Scallop Pecten maximus Width to 12cm
Iconic free-living bivalve. Sub-littoral on sand and gravel substrates, but shells often washed up. SHELL is circular in outline, with up to 17 radiating ribs and square-cut ‘ears’ at base (almost equal). In life, cupped right valve lies on substrate, flat left valve is uppermost. Swims freely. STATUS Widespread on S and W coasts; fairly common, although badly depleted by commercial fishing.
Queen Scallop Aequipecten opercularis Width to 90mm
Similar to Great Scallop but with subtle differences in outline and ‘ears’. Found on lower shore and sub-littorally on mixed shores; young animals are attached by byssus threads. SHELL is rounded-oval in outline, with up to 20 radiating ridges. Both valves are cupped (left more so than right), with 1 ‘ear’ longer than the other (especially on right valve). STATUS Widespread on S and W coasts; fairly common, although badly depleted by commercial fishing.
Variegated Scallop Chlamys varia Length to 60mm
Well-marked scallop. Found on rocky shores, attached by byssus threads or free-living. SHELL is elongate-oval, marbled reddish brown and with 25–35 spiny ridges; spines are often worn in strandline shells. Ribbed basal ‘ears’ are much longer on 1 side than other; ‘ear’ on right valve has byssal notch. STATUS Fairly common, least so on the E coast.
Humpback Scallop Chlamys distorta Length to 50mm
Distinctive distorted bivalve, often hard to recognise as a scallop. Found on lower shore on rocky coasts. SHELL is elongate-oval with up to 70 radiating ribs. One basal ‘ear’ is larger than other but these are not always pronounced. Right valve is attached to rock and shape moulds to substrate. STATUS Commonest in the S and NW.
Tiger Scallop Palliolum tigerinum Width to 25mm
Small, fairly distinctive scallop. Found on sheltered shores, on gravel and coarse sand; at low water and in sub-littoral zone. SHELL is rounded-oval, marbled reddish brown and with concentric growth rings, usually smooth but sometimes with 30 or so subtle ribs. Ribbed basal ‘ears’ are much longer on one side than the other; ‘ear’ on right valve has byssal notch. STATUS Widespread; commonest in the W, mostly absent from the E.
Common Oyster Ostrea edulis Width to 90mm
Portuguese Oyster
Distinctive and iconic bivalve. Found on muddy gravel seabeds; mostly sub-littoral but shells sometimes washed up. SHELL is circular to oval in outline with concentric scaly ridges. Outside colour is greyish white; shell interior has mother-of-pearl coating. Left valve is cupped, right valve is flattish. STATUS Still fairly common on S and W coasts but locally depleted or destroyed by commercial exploitation. SIMILAR SPECIES Portuguese Oyster Crassostrea gigas (length to 25cm) is mostly sub-littoral, on gravel and mixed substrates. Shell is irregularly oval. Outer surface has irregular concentric, flaky ridges; inner surface has mother-of-pearl coating. Introduced, now established in the S.
Gaping File Shell Limaria hians Length to 25mm
Constructs a ‘nest’ of debris on lower shore in crevices and under rocks. SHELL is narrowly oval, recalling a slender scallop in outline; in profile, gap between valves is diagnostic. In life, orange tentacles project. STATUS Local and scarce, least so in the NW.
Tiny bivalve, recognised by its size, colour and location: lives on upper shore and in splash zone on rocky coasts, among Lichina clumps and empty barnacle shells. SHELL is reddish brown, rounded in outline and plump in profile. STATUS Widespread and locally common in the S and W, but mostly absent from the E coast. SIMILAR SPECIES Turtonia minuta (width to 3mm) has 3 small teeth on inside of shell below umbo (Lasaea sp. have lateral teeth but only 1 tooth below umbo). Yellow-brown and oval with a prominent umbo. Found on rocky shores, in crevices and empty barnacle shells. Commonest in the N and NW.
Hard-shell Clam Mercenaria mercenaria Width to 11cm
Robust bivalve. Lives in muddy substrates, mostly sub-littoral but sometimes at low-tide level. SHELL is thick and roughly triangular, with rounded outer margins. Surface has numerous concentric bands; typically grey-brown, tinged violet towards margin. STATUS Introduced from North America (where known as Qahog); now local on the S coast.
Icelandic Cyprine Arctica islandica Width to 11cm
Robust bivalve. Sub-littoral in muddy sand but shells often washed up. SHELL is thick and rounded-oval. Periostracum is dark brown but peels and wears in empty shells. Inside is white with 3 cardinal teeth and 1 lateral tooth. STATUS Widespread and common, except in the SE. NOTE Contender for world’s longest living animal – can live for several hundred years.
Pullet Carpet Shell Tapes corrugata (Venerupis senegalensis) Length to 50mm
Manila Clam
Well-marked bivalve. In life, lives in sub-littoral sand and gravel; empty shells often washed up. SHELL is elongate-oval, with numerous concentric ridges and radial striations. STATUS Scattered and local, mainly on S and W coasts. SIMILAR SPECIES Manila Clam Ruditapes philippinarum (length to 60mm) is more rounded and has dark rays; introduced, now local on S coast.
Rayed Artemis Dosinia exoleta Width to 50mm
Striking bivalve. Lives buried in muddy sand and gravel; empty shells often washed up. SHELL is almost circular in outline, but with fairly prominent umbo. Outer surface has numerous concentric ridges and is usually buffish brown with radiating darker brown bands; inner surface is shiny. STATUS Widespread but local, mainly in the S and W.
Warty Venus Venus verrucosa Width to 60mm
Robust bivalve with a sculptured shell. Sub-littoral in gravel and coarse sand; empty shells are washed up. SHELL is oval with 20 or so raised concentric ridges. On posterior part of shell, ridges are ‘cut’, forming wart-like projections; these wear in beached shells. STATUS Scattered distribution, mainly in Hampshire and Dorset coast, and N Wales.
Striped Venus Chamelea gallina Width to 40mm
Well-marked bivalve. On sandy shores, mainly sub-littoral but empty shells often washed up. SHELL is broadly triangular with curved margin. Surface is buffish brown, with concentric ridges and radiating (often interrupted) darker brown rays. STATUS Widespread and fairly common on suitable coasts; absent from most of SE England.
Thin Tellin Angulus tenuis Width to 26mm
Thin, rather delicate bivalve. Lives in sand on lower shore. SHELL is angular-oval; anterior margin is rounded, posterior margin pointed. Outer margin has fine concentric ridges; colour variable but often yellow-brown with reddish bands. STATUS Widespread and locally common on suitable coasts.
Baltic Tellin Macoma balthica Width to 25mm
Small, plump bivalve. Lives in muddy sand on lower shore, often in estuaries. SHELL is rounded-oval; anterior margin rounded, posterior margins more angular. Colour variable but often yellowish brown with reddish bands. STATUS Widespread and common.
Common Cockle Cerastoderma edule Width to 45mm
Iconic bivalve and our commonest cockle species. Lives in sand and muddy sand; tolerates a range of salinities. SHELL is rounded-oval and thick. Outer surface is grey-brown with 24 or so radiating ribs; inner surface is whitish, with ribs showing on outer margin only (not extending beyond pallial line). STATUS Widespread and locally common on suitable coasts.
Lagoon Cockle Cerastoderma glaucum Width to 35mm
Similar to Common Cockle but with angular outline and thin shell. Favours brackish lagoons. SHELL is rounded-oval in outline with straight (not curved) posterior margin. Outer surface is grey-brown with 24 or so radiating ribs; inner surface is whitish, with ribs visible across whole shell. STATUS Local, mainly in the S and SE; occurrence is limited by its specialised habitat requirements.
Rough Cockle Acanthocardia tuberculata Width to 90mm
Plump bivalve. Lives in muddy sand on lower shore and below. SHELL is rounded-oval. Outer surface is grey-brown with 18–20 ridged, radiating ribs, these armed with spines and tubercles (worn in beached shells); inner surface is whitish, with ribs showing on outer margin only (not extending beyond pallial line). STATUS Very locally common on the S coast only.
Spiny Cockle Acanthocardia aculeata Width to 95mm
Distinctive bivalve. Sub-littoral in muddy sand and gravel; empty shells washed up. SHELL is angular-oval with straightish posterior margin. Outer surface is grey-brown with 20 or so ridged, radiating ribs, these armed with spines (worn in beached shells); inner surface is whitish, with ribs visible across whole shell. STATUS Very local on the S coast.
Prickly Cockle Acanthocardia echinata Width to 70mm
Plump bivalve. Sub-littoral in muddy sand and gravel; empty shells washed up. SHELL is rounded-oval. Outer surface is grey-brown with 20–23 ridged, radiating ribs, these armed with spines (worn in beached shells); inner surface is whitish, with ribs visible across whole shell. STATUS Widespread and locally common, least so on the E coast.
Norway Cockle Laevicardium crassum Length to 70mm
Distinctive cockle. Sub-littoral in sand and gravel; empty shells washed up. SHELL is oval, pointed at hinge end. Outer surface is brown with 50 or so indistinct ribs; inner surface is whitish, tinged pink, with ribs creating crenulated margin. STATUS Widespread and locally common, except on the E coast.
Thick Trough Shell Spisula solida Width to 50mm
Robust bivalve. Found in sand, on lower shore and sublittoral. SHELL is triangular in outline with curved outer margin, distinct umbo and fine concentric lines. Outer surface is yellowish-brown but worn shells are paler. Inside, note serrated lateral teeth. STATUS Widespread and locally common, least so on E coast.
Rayed Trough Shell Mactra stultorum Width to 50mm
Distinctive bivalve. Lives in sand on lower shore; empty shells often washed up. SHELL is triangular with a curved outer margin and concentric lines on outer surface. Typically pale brown with darker radiating ‘rays’. STATUS Widespread and fairly common but absent from much of NW and SW Britain.
Common Otter Shell Lutraria lutraria Width to 125mm
Common Otter Shell, living animal
Large bivalve. Lives in sand on lower shore; buries deep and seen only as washed-up shells. SHELL is elongate-oval. Outer surface has concentric lines and ridges; typically pale brown with flaky, dark brown coating around margin. STATUS Widespread but scattered; commonest in S England, Wales and N Scotland.
Banded Wedge Shell Donax vittatus Width to 35mm
Attractive bivalve. Lives in sand, on lower shore and in sub-littoral zone; empty shells often washed up. SHELL is elongate-triangular. Outer surface has numerous fine, radiating and concentric lines and concentric bands of colour; inner surface has patches of violet-blue. Both surfaces have crenulated outer margin. STATUS Widespread but scattered; commonest on S and NW coasts of England, and Welsh coast.
Peppery Furrow Shell Scrobicularia plana Width to 60mm
feeding trails
Characteristic bivalve of estuaries. Tolerates brackish water and buries in mud; siphons create characteristic star-shaped patterns on surface when feeding. SHELL is oval with pointed umbo. Outer surface has numerous fine, concentric lines and is often greyish white, tinged yellow around margin; inner surface is shiny. STATUS Widespread and locally common only in the S.
Faroe Sunset Shell Gari fervensis Width to 50mm
Faroe Sunset Shell with hole drilled by Necklace Shell
Attractive bivalve. Mostly sub-littoral in sand, but often washed up. SHELL is elongate-oval to oblong. Outer surface has concentric rings, and ridge running diagonally from umbo to posterior margin; typically pinkish lilac with darker concentric bands and radiating ‘rays’. Inner surface is shiny pinkish lilac. STATUS Widespread and locally common.
Sand Gaper Mya arenaria Width to 14cm
Robust, thick-shelled bivalve. Lives buried in muddy sand on lower shore and below; often found in estuaries. Empty shells are often washed up. SHELL is oval in outline, anterior end rounded, posterior end more pointed. Outer surface has concentric ridges; brown in life but strandline shells often worn white. Left valve has spoon-shaped projection near hinge. STATUS Widespread and locally common on suitable shores.
Blunt Gaper Mya truncata Width to 70mm
Robust, thick-shelled bivalve. Lives buried in clean muddy sand, typically in shallow sub-littoral zone, but empty shells are washed up. SHELL has rectangular outline with truncate posterior margin. Outer surface has rough concentric ridges. STATUS Widespread and locally common on suitable shores.
Basket Shell Corbula gibba Width to 15mm
Small, robust bivalve found in muddy sand; lower shore and sub-littoral. SHELL has unequal oval valves, flattish left valve fitting inside lip of convex right valve. STATUS Widespread and locally common; particularly on S England and S Wales coasts, scarce and patchy on E coast.
Pandora inaequivalvis Length to 25mm
animal in situ
Unusual and distinctive bivalve. Mainly sub-littoral in sand but sometimes washed up alive or as empty shells. SHELL comprises unequal, slightly translucent white valves. Lower valve is shallowly concave, upper is almost flat. STATUS Local and generally scarce; sites include Studland Bay and Bracklesham Bay.
Norway Shipworm Nototeredo norvegica Tube length to 50cm
pallet
shell
tube
Norway Shipworm, tubes in situ
Atypical bivalve, hardly recognisable as a mollusc. Lives in a cylindrical (often U-shaped) calcified tube in floating timber (once boats, nowadays usually driftwood). SHELL comprises paired, angular, plate-like valves used for boring into wood. Animal’s worm-like body ends in 2 siphons that appear at open end of tube; can be closed using calcified paddle-shaped plates (pallets). STATUS Records are scattered and patchy, mostly from beaches in the S and W. SIMILAR SPECIES Great Shipworm Teredo navalis is similar but with straight-sided pallets.
Pod Razor Shell Ensis siliqua Length to 20cm
Pod Razor Shell, empty shells washed up after storm
Distinctive bivalve. Lives buried, vertically, in fine sand on lower shore and in shallows; dead shells often washed up. SHELL is almost straight, with parallel sides and truncate ends; siphons protrude from anterior end, muscular foot from posterior end. STATUS Widespread; some populations have been ruined by exploitation, but still locally common on some suitable shores.
Common Razor Shell Ensis ensis Length to 12cm
Common Razor Shell, living animal
Distinctive bivalve. Lives buried, vertically, in fine sand on lower shore and in shallows; dead shells often washed up. SHELL is evenly curved in outline, with parallel sides; anterior end is curved, posterior end truncate. STATUS Widespread; many populations have been ruined by exploitation, but still locally common on some suitable shores.
Grooved Razor Shell Solen marginatus Length to 12cm
Grooved Razor Shell, living animal
Elongate bivalve. Burrows in sand; lower shore and sub-littoral zone. Dead shells often washed up. SHELL has straight, parallel sides and truncate ends; note distinct marginal groove near anterior end of both valves. STATUS Locally common on the S coast, NW Norfolk and W coast N to Lancashire.
Pod-like bivalve. Burrows in fine sand; lower shore and sub-littoral zone. SHELL is elongate-rectangular in outline; posterior end is blunt, anterior end tapers. STATUS Locally common only off coasts of Wales and NW England.
Wrinkled Rock Borer Hiatella arctica Length to 4cm
Wrinkled Rock Borer, young animal
Robust bivalve that bores into soft rocks and attaches by byssal threads in rock crevices; lower shore and sub-littoral zone. SHELL is rectangular in outline. Valve outer surface is ridged and often worn. STATUS Widespread and locally common except off coasts of E England.
Common Piddock Pholas dactylus Length to 14cm
Robust bivalve that bores into soft rock, compacted clay and peat; lower shore and sub-littoral zone. SHELL is narrowly oval in outline, pointed at 1 end. Valves ‘gape’ and outer surfaces have toothed, concentric ridges that aid boring. STATUS Widespread but local; commonest in the S, absent from the N.
Oval Piddock Zirfaea crispata Length to 9cm
Distinctive bivalve that bores into soft rocks, submerged wood, peat and clay; lower shore and sub-littoral zone. SHELL is angular-oval in outline. Valves ‘gape’ and outer surfaces have concentric, toothed ridges and transverse ridge from umbo. STATUS Widespread but local; absent from much of the SW and NW.
White Piddock Barnea candida Length to 6cm
White Piddock, living animal in situ
Recalls Common Piddock but shell is narrower and gapes only at posterior end. Bores into peat and soft rocks; lower shore and sub-littoral zone. SHELL is elongate-oval with concentric, toothed ridges. STATUS Widespread and locally common, mainly in SE and NW England, and Wales.
American Piddock Petricola pholadiformis Length to 8cm
Boring bivalve, found in compacted clay and mud; lower shore and sub-littoral zone. SHELL is narrowly rectangular in outline. Outer surface is strongly ridged and often stained orange by sediment. STATUS Introduced North American species, now locally common, mainly in the SE.
Looping Snail, living animal
Truncatella subcylindrica Height to 5mm
Small but distinctive shell. Found on upper shore of estuaries and mudflats, typically in interstices between pebbles. SHELL is cylindrical; spire tip is snapped off except in small, young animals. Walks by using foot in a ‘looping’ manner. STATUS Very local, from Cornwall to Essex.
Mouse-eared Snail Myosotella myosotis Length to 8mm
Small snail, found on upper reaches of estuaries and just above splash zone on sheltered shores. Usually lives under rotting seaweed and eelgrass debris. SHELL is narrowly oval and pointed at apex. Shell mouth is oval with thickened outer and inner lips, each with 3 or more ‘teeth’. STATUS Widespread and locally common except in the N.
Two-toothed White Snail Leucophytia bidentata Length to 6mm
Distinctive small snail. Lives among stones and under seaweed debris on upper shore, on sheltered rocky coasts. SHELL is narrowly oval and creamy white. Shell mouth is narrowly oval, inner lip thickened with 2 ‘teeth’. STATUS Local, mainly in the S.
Lagoon Snail Paludinella littorina Length to 2mm
Minute snail. Lives in caves and crevices, just above high-tide line. Easily overlooked or mistaken for juvenile periwinkle. SHELL is rounded, glossy, semi-transparent and yellowish grey. STATUS Local, in the SW only, from the Isle of Wight to S Wales.
Pointed Snail Cochlicella acuta Length to 15mm
Distinctive shall. Found in dunes and coastal calcareous grassland. SHELL is narrowly pointed. Markings are variable: sometimes whitish with narrow dark band on bottom whorl; or with much more extensive brown markings. STATUS Widespread and locally common in the S and W; absent from the E.
Heath Snail Helicella itala Diameter to 18mm
Well-marked snail of dunes and coastal calcareous grassland. SHELL is a flattened spiral, variably marked with spiral brown bands. STATUS Widespread and locally common except in the NE.
Banded Snail Cernuella virgata Diameter to 18mm
Variably marked snail of dunes and coastal calcareous grassland. SHELL is rather globular in outline, with tight spiral whorls; usually marked with a dark spiral band (sometimes several on largest whorl). STATUS Widespread and locally common except in the N.
Kentish Snail Monacha cantiana Diameter to 15mm
Wayside snail, common in coastal habitats, especially in dunes in the N of its range. SHELL is rather globular, mainly pale buff and flushed darker brown towards mouth (inside and out). STATUS Widespread and locally common in England; scarcer and almost exclusively coastal in Wales.
Wrinkled Snail Candidula intersecta Diameter to 12mm
Distinctive snail of dunes and coastal grassland. SHELL is flattened-globular with tightly packed whorls; these are marked with spirally radiating ridges and dark lines, creating a ‘wrinkled’ appearance. STATUS Widespread and locally common except in the NW.
White-lipped Snail Cepaea hortensis Diameter to 18mm
White-lipped Snail, living animal
Distinctive snail; 1 of 2 very similar species. Found in dunes, coastal grassland and scrub. SHELL is globular with variable forms: typically either uniform yellow or yellow with dark spiral bands. Note the diagnostic white lip to shell mouth. STATUS Widespread and locally common; exclusively coastal in the N. SIMILAR SPECIES Brown-lipped Snail C. nemoralis has similarly variable markings but diagnostic dark brown lip. Widespread and locally common, but absent from much of the N.
Garden Snail Cornu aspersum Diameter to 40mm
Familiar large snail. Found in dunes, coastal grassland and scrub. SHELL is marbled brown and black, often rather worn in older specimens. STATUS Widespread and generally common, but local and scarce in the far N.
Great Black Slug Arion ater Length to 10cm
Great Black Slug, brown form
Large and distinctive slug, seen in 2 main colour forms. Occurs in a wide range of habitats inland, but particularly common on coastal cliffs, paths and dunes. ADULT is usually either uniformly black or orange-brown. STATUS Widespread and common throughout.
Common Cuttlefish Sepia officinalis Length to 35cm
Common Cuttlefish, eggs
Cuttlebone
Common Cuttlefish, young animals
Impressive and distinctive cephalopod mollusc. Found on sandy and gravel substrates, mainly sub-littoral but inshore (for spawning) in late spring and summer. Cuttlebones (internal shell) often washed up. ADULT has oval body with lateral fins, large eyes, and arms with 4 rows of suckers. STATUS Locally common off coasts of S and SW England, and Wales.
Little Cuttlefish Sepiola atlantica Length to 20mm
Little Cuttlefish, swimming
Little Cuttlefish, resting
Beautiful little cephalopod mollusc. Found in shallows at low tide on sandy shores, also in pools. ADULT has compact, rather rounded body, with rounded, slightly frilly fins and relatively large head, eyes and tentacles. Head is fused to mantle on dorsal surface, between eyes. Ability to change colour is impressive. STATUS Widespread but local; commonest in the S and W. SIMILAR SPECIES Stout Bobtail Rossia macrosoma (length to 6cm) has rounded fins and head is not fused, dorsally, to mantle. In the NW only.
Common Squid Loligo vulgaris Length to 70cm
Common Squid, eggs
Common Squid, young animals
Slender, fast-swimming cephalopod mollusc. Usually in open sea but sometimes in shallow inshore waters in spring and summer. ADULT has elongate, torpedo-shaped body with triangular fins and large eyes. Most tentacles are rather short; 2 are long and clubbed, with very large median suckers. STATUS Locally common only on S and W coasts. SIMILAR SPECIES Long-finned Squid L. forbesi is slightly smaller (length to 60cm); median suckers on tentacle club are only marginally larger than lateral ones. Range is similar to that of Common Squid.
Curled Octopus Eledone cirrhosa Length to 50cm
Curled Octopus, swimming
Our most commonly encountered octopus. Lives on rocky coasts. Usually sub-littoral, but sometimes found in pools or brought up in crab pots. ADULT has a smooth, sac-like body and large eyes, mantle cavity opening via a siphon. Tentacles are long and very mobile, often curling at tip; tentacles have single row of suckers. Animal can change colour rapidly to match background. STATUS Locally common only in the SW and on W coasts. SIMILAR SPECIES Common Octopus Octopus vulgaris (length to 90cm) has a warty texture, relatively smaller eyes and 2 rows of suckers on tentacles. Very local on S and W coasts.