Glycymeris glycymeris

(Linné, 1758)

Shell thick, robust; almost circular in outline, anterior hinge line curving more abruptly downwards than posterior. Umbones central, scarcely inclined anteriorly; cardinal area very elongate. Periostracum coarse, velvety to touch, usually remaining as a broad band around margin. Sculpture of fine concentric lines and radiating striae, growth stages clear. Hinge line with 6-12 teeth in each of two series, on either side of a smooth area below umbo; in young shells these are continuous. margin crenulate. Adductor sears and pallial line well-marked (G. glycymeris-drawing).

Up to 65 mm long.

Surface dull; brown, yellow, or light purplish-red, either uniformly coloured or in irregular concentric zigzags on a cream background; periostracum dark brown. Inside of shell glossy, white, brown, or reddish, often with irregular patterns.

Animal has no siphons, but the edge of the mantle is somewhat contracted and protruded at the hinder side of the shell; at this part, too, it is studded with a great number of black eye-spots (G. glycymeris-animal).

A shallow burrower in fine shell-gravels, or sandy-muddy gravels offshore to about 100 m.

Distributed from Norway south to the Mediterranean and west Africa (Distr. G. glycymeris). Dead shells often accumulate in vast deposits in some areas, such as the western end of the English Channel.