Shell is thick, heavy, rounded to squared, occasionally inflated and covered with three or more posterior folds or ridges. Umbo raised above hinge line. Epidermis is yellowish-green to light brown in juveniles, becomes dark green, brown or black with age. Inside shell beak cavity medium to deep; pseudocardinal teeth large and thick; lateral teeth serrate, straight to slightly curved; nacre (lining) white and frequently stained.
Similar species: Washboard is larger with more complex folding and has bumps on the anterior third of shell.