Shell is stout, inflated, oval to rectangular and thick with a posterior wing; round anterior end and broadly rounded posterior ridge; posterior end bluntly squared (females) to sharply rounded (males). Umbo is broad and raised above hinge line. Epidermis is smooth and glossy, dark brown, becomes black with age; dark green rays on young, later fading. Inside shell beak cavity is broad and deep; pseudocardinal teeth relatively small, roughened and pointed; lateral teeth prominent, blade-like and slightly curved; nacre (lining) pinkish-purple to deep purple.
Similar species: Pink heelsplitter is lighter in color and less inflated or stout and its nacre is lighter in color.