Any of a class (Lamellibranchia) of bivalve mollusks (as clams, oysters, and mussels) that have the body bilaterally symmetrical, compressed, and enclosed within the mantle and that build up a shell whose right and left parts are connected by a hinge over the animal back.

【动】瓣鳃类(如蛤、牡蛎、蚌)。