(Montagu, 1803)
Description (shell);
Shell very thin and fragile, roughly square in outline, umbones small, just anterior to midline. Sculpture of fine concentric lines, most conspicuous close to distinct growth stages; surface of both valves marked with dense punctulations, reminiscent of a brachiopod. Hinge plate distinct; right valve with one minute cardinal tooth and single anterior and posterior lateral teeth, left valve with small cardinal tooth and single anterior and posterior lateral teeth. Inside of shell with external punctulation showing through. Adductor scars about equal, pallial line diffuse.
Size:
Up to 12 mm long.
Colour:
White, translucent, periostracum thin and inconspicuous. Inside of shell translucent.
Animal:
White. The mantle, which is fringed with long tentacles, protrudes nearly all round. One tentacle has developed abnormally, and when the creature crawls along it waves this tentacle about, apparently using it as a sense-organ.The bluish foot is streaked with white and can be flattened in such manner that it resembles the foot of a snail. Excurrent siphon is short.
Habitat:
In silty sand and fine gravel from ELWS into shallow sublittoral; this species lives in or close to burrows of callianassid shrimps (Upogebia spp.).
Distribution:
Distributed from Norway to the Mediterranean; in British waters, most frequent off the southern and western coasts (Distr. L. squamosum).