The overall shape is ovate. The valves are the same size and shape (equivalve), and there is no gape when they are closed. Ornamentation consists of growth lines, comarginal and radial ribs. The radial ribs are more prominent than the comarginal ribs. All ribs become stronger anteriorly and posteriorly. The central area of the shell is smoother, but the comarginal ribs become slightly stronger as the animal grows. The lunule is elongate, varies in width and can extend up to 2/3 of the anterior dorsal margin. The umbo points slightly anteriorly. The escutcheon is not well defined, but can be elongate and smoother than the overall shell; it also may be more prominent on the left valve.
The exterior coloration is highly variable and not indicative of the species (Shaw 1956). Generally, the exterior color is a light tan or brown with a dark brown lunule. There may be radial or comarginal brown stripes, or brown mottling. The interior color is white and there may be purple coloration around the margin. The purple is stronger on the posterior margin, under the ligament and in the pallial sinus.
The ligament is exterior and supported by nymphal ridges. There are three cardinal teeth on each valve. On the left valve, the central tooth is bifid, and the anterior and posterior teeth are not bifid. On the right valve, the posterior and central teeth are bifid, and the anterior tooth is not bifid. There are no lateral teeth. The anterior adductor muscle scar is slightly smaller than the posterior adductor muscle scar. The pallial sinus is rounded and extends to approximately the end of the ligament in length.
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