'Acephala' definitions:
Definition of 'Acephala'
From: GCIDE
- Lamellibranchia \La*mel`li*bran"chi*a\, Lamellibranchiata \La*mel`li*bran`chi*a"ta\, n. pl. [NL. See lamella, and Branchia, Branchiate.] (Zool.) 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. [1913 Webster +PJC]
- 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. [1913 Webster]