Beak cavity very deep. Description Shell solid, heavy, rounded or oval, and inflated. Anterior end rounded, posterior end rounded or bluntly pointed. Dorsal margin slightly rounded, ventral margin curved, occasionally straight. Umbos low, inflated, about even with hinge line and curved downward.
Beak sculpture consists of a few very weak ridges, apparent only in extremely small shells.
Shell smooth with slightly elevated ridges indicating periods of growth. Periostracum rayless, light brown in young shells, becoming dark brown to black in older individuals. Beak cavity very deep. Nacre pearly white, iridescent posteriorly. Habitat Large rivers in sand and gravel.