Scrobicularia plana

(da Costa, 1778)

Description (shell):
Shell thin and brittle, oval, umbones just anterior to midline. Sculpture of numerous, fine concentric lines and grooves. Internal ligament supported in each valve by a triangular, backwardly directed chondrophore; two small cardinal teeth anterior to chondrophore in right valve, a single one in left. Adductor scars and pallial line not readily apparent in fresh material. Pallial sinus broad, lower edge largely fused with pallial line; posteriorly, cruciform muscle scars may be apparent (S. plana-drawing 2).

Up to 65 mm long.

Dull white, yellowish, or grey, usually darkest about the growth lines. Periostracum thin, conspicuous only at margins. Inner surfaces glossy, white or yellowish (S. plana-drawing).

(S. plana-animal).

Intertidal only, burrowing in soft substrata in estuaries and tidal flats, in conditions of fluctuating salinity. Often abundant.

Widely distributed, ranges from Norway to the Mediterranean and West Africa (Distr. S. plana).