A*ceph"a*la (#), n. pl. [NL., fr. Gr. , adj. neut. pl., headless. See Acephal.] Zool.
That division of the Mollusca which includes the bivalve shells, like the clams and oysters; -- so called because they have no evident head. Formerly the group included the Tunicata, Brachiopoda, and sometimes the Bryozoa. See Mollusca.
© Webster 1913.