Fusconaia ebena (Lea, 1831)
Other common names: None.
Key characters: Round, heavy, thick, brown or black shell without rays or pustules. Beak cavity very deep.
Description: Shell solid, heavy, rounded or oval, and inflated. Anterior end rounded, posterior end rounded or bluntly pointed. Dorsal margin slightly rounded, ventral margin curved, occasionally straight. Umbos low, inflated, about even with hinge line and curved downward. Beak sculpture consists of a few very weak ridges, apparent only in extremely small shells. Shell smooth with slightly elevated ridges indicating periods of growth. Periostracum rayless, light brown in young shells, becoming dark brown to black in older individuals. Length to 4 inches (10.2 cm).
Pseudocardinal teeth very heavy and well developed; two in the left valve, two in the right. Lateral teeth serrated and curved; two in the left valve, one in the right. Beak cavity very deep. Nacre pearly white, iridescent posteriorly.
Habitat: Large rivers in sand and gravel.
Status: Endangered in Missouri and Wisconsin. Threatened in Ohio. Species of Special Concern in Illinois and Minnesota.