What is "equivalve"

Equivalve \E"qui*valve\, Equivalved \E"qui*valved\, a. [Equi- + valve.] (Zo["o]l.) Having the valves equal in size and from, as in most bivalve shells.

a. (context zoology of the shells of a bivalve mollusc English) Having valves of the same size (as is normal) n. Any bivalve mollusc whose valves are of the same size.