Bivalve

Bivalve, a term applied to those animals in which the shell consists of two separate halves or valves. Such are the Lamellibranchiata, in which the two valves may be equal, as in the cockle, or unequal, as the oyster; the Brachiopoda, in which the valves are always unequal though each valve may be bilaterally symmetrical. Among the Crustacea there are the Ostracoda and some Phyllopoda.