Pleurobema plenum (Lea, 1840)
Other common names Pigtoe.
Key characters Shell shaped like an equilateral triangle, with a brown, satinlike appearance and a moderately deep beak cavity.
Similar species All other pigtoes (Fusconaia and Pleurobema).
Description Shell somewhat triangular, higher than long, moderately thick, and inflated. Anterior and posterior ends rounded. Dorsal and ventral margins curved. Umbos inflated and elevated above the hinge line. Beak sculpture of two or three elevated ridges. Shell textured, with a satin-like appearance. Periostracum yellowish brown or light brown in small shells, becoming dark brown in adults, with faint green rays visible near the beaks in some shells. Length to 4 inches (10.2 cm).
Pseudocardinal teeth well developed; two in the left valve, one in the right. Lateral teeth straight. Beak cavity moderately deep. Nacre usually white, occasionally pink.
Habitat Medium to large rivers in sand or gravel.
Status Federally Endangered.