That division regarding the Mollusca including the bivalve shells such as the clams and oysters so called since they have no obvious mind Formerly the group included the Tunicata Brachiopoda and often the Bryozoa See Mollusca
- That unit of this Mollusca which include the bivalve shells, like clams and oysters; -- so-called because they don't have any obvious head. Formerly the group included the Tunicata, Brachiopoda, and quite often the Bryozoa. See Mollusca.
The Chitons and their allies were placed under the Gastropoda, as a distinct branch called Isopleura, and for the Acephala de Blainville's name Lamellibranchia was substituted.