Size: Up to five inches.
Shape: Obovate to trapezoidal. Slightly laterally compressed. The shell has an angular ridge that runs from the beak to the basal part of the posterior margin; this ridge may be less angular in specimens living in slow-moving water. The ventral margin is usually straight. The shell is heavier than that of all other native species.
Periostracum: Color yellowish-brown to brown or black. No shell rays or sculpturing on the shell.
Lateral Teeth: Absent.
Pseudocardinal Teeth: The right valve has one small tooth and the left valve has either one small tooth or none at all. The teeth are small and compressed, sometimes hard to distinguish.
Nacre: Usually white, but sometimes salmon-colored in fresh specimens and pale blue toward the posterior margin and beak cavity.