Diplodonta rotundata

(Montagu, 1803)

Description (shell):
Shell thin, brittle, tumid; irregularly oval, posterior half deeper than anterior. Surface smooth or silky in unworn specimens. Lunule indistinct; escutcheon well-marked, deep, ligament distinct (D. rotundata-drawing). Left valve with bifid anterior cardinal tooth and a single posterior cardinal tooth; right valve with single anterior and bifid posterior. Both valves with single anterior and posterior lateral teeth. Sculpture of very fine concentric lines; growth stages clear, often coarse in larger specimens. Anterior adductor scar dorso-ventrally elongate, comma-shaped, closely applied to the pallial line (D. rotundata-drawing 2).

Up to 30 mm long.

Colour white, periostracum light yellowish brown. Inner surface of shell white, lustrous.

White, with large free lips, and the mantle edges are united, save for the large aperture on the lower margin where the foot emerges, and for the incurrent and excurrent orifices on the lower margin.

In sand and gravel, offshore to about 70 m.

Reported from the English Channel and the south and west Irish coasts, south to the Mediterranean and west Africa (Distr. D. rotundata).