Lampsilis abrupta (Say, 1831)
Other common names: Ohio mucket, tan mucket, square mucket.
Key characters: A rounded to slightly elongate shell, thick, inflated, smooth, and yellowish brown; posterior end bluntly pointed in males, truncated in females.
Description: Shell round to elliptical, solid, and inflated. Anterior end rounded, posterior end bluntly pointed in males, truncated in females. Dorsal margin straight, ventral margin straight to slightly curved. Umbosturned forward and elevated above the hinge line. Beak sculpture, if visible, of three or four double-looped ridges. Shell smooth, yellow or yellowish green and rayless or with faint green rays. Length to 4 inches (10.2 cm).
Pseudocardinal teeth triangular, thick, divergent; two in the left valve, one in the right, occasionally with a smaller tubercular tooth in front. Lateral teeth short, heavy, and relatively thick. Beak cavity deep. Nacre pink or white, iridescent posteriorly.
Habitat: The lower Mississippi and Ohio rivers and their larger tributaries in gravel or sand.
Status: Federally Endangered.