Spisula solida

The surf clam (Spisula solida) is a medium-sized marine clam, or bivalve mollusc, found in the Eastern Atlantic from Iceland and northern Norway to Portugal and Spain. Up to 5 cm long, like many clams, the surf clam is a sediment-burrowing filter feeder. Right and left valve of the same specimen:

This species of clam is found in sandy bottom in the sublittoral zone. It is commonly found in the North Sea, Baltic Sea and the Irish Sea.