1) Class 2) Class bivalvia 3) Class lamellibranchia 4) Class pelecypoda 5) Lamellibranchia 6) Oysters 1) Lamellibranchia 
The Bivalvia, in previous centuries referred to as the Lamellibranchiata, Conchifera, and Pelecypoda, comprise a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. They have no head, and they also lack a radula. Bivalves include clams, oysters, cockles, mussels, scallop...
[n] - oysters
class Bivalvia noun oysters; clams; scallops; mussels