Pimpleback (Quadrula pustulosa)

Shell Characteristics
Rounded, truncate posteriorly, valves thick, moderately inflated; scattered pustules on posterior 2/3 of valve-varies from none to numerous; periostracum brown, with a broad green ray on umbo. Beak sculpture obscure. Teeth well developed, nacre white. Length to 3 1/2 inches. Similar to mapleleaf, purple pimpleback, wartyback, and winged mapleleaf.

Distribution and Habitat
Medium to large rivers in soft or coarse substrate and flowing water. Widespread and locally common in the Mississippi River below St. Anthony Falls and St. Croix River drainage; uncommon to rare in the Minnesota River Drainage. Commercially valuable.