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.
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.