What is "lamellibranchiata"

Lamellibranchia \La*mel`li*bran"chi*a\, Lamellibranchiata \La*mel`li*bran`chi*a"ta\, n. pl. [NL. See lamella, and Branchia, Branchiate.] (Zo["o]l.) An earlier name for the class of Mollusca including all those that have bivalve shells, as the clams, oysters, mussels, etc., now called Pelecypoda or Bivalvia.

Note: They usually have two (rarely but one) flat, lamelliform gills on each side of the body. They have an imperfectly developed head, concealed within the shell, whence they are called {Acephala}. Called also Conchifera, and Pelecypoda. See Bivalve.