Also called Bivalves. A common fossil in marine rock. Pelecypods have shells with two valves that are the same size and shape. The shells often show growth lines, and radiating ridges and grooves, useful for identification. Oysters, mussels, and clams are living types.

a division of mollusks, commonly called clams.

burrowing mobile marine with compressed bodies enclosed in hinged bivalve shells; includes clams, oysters, mussels