The Collaborative International Dictionary
Inequivalve
Inequivalve \In*e"qui*valve\, Inequivalvular \In*e`qui*val"vu*lar\, a. (Zo["o]l.) Having unequal valves, as the shell of an oyster.
Wiktionary
inequivalve
a. (context zoology of the shells of a bivalve mollusc English) Having valves of different sizes n. Any bivalve mollusc whose valves are of different sizes.