Alasmidonta viridis (Rafinesque, 1820)
Other common names: None.
Key characters: Small, somewhat rectangular shell, high posterior ridge, wavy green rays on posterior half of the
shell, poorly developed lateral teeth.
Similar species: Elktoe.
Description: Shell small (usually about an inch), somewhat inflated, thin in young individuals to moderately thick in adults. Anterior end rounded, posterior end squared or truncated. Posterior ridge high and rounded, posterior slope flattened. Ventral margin straight or slightly arched. Umbos full and elevated above the hinge line. Beak sculpture of three or four elevated ridges or loops. Shell smooth to rough and yellowish green with numerous wavy green rays, particularly on the posterior half of the shell. Length to 1.5 inches (3.8 cm).
Pseudocardinal teeth triangular; two in the left valve, one in the right. Lateral teeth poorly developed, generally appearing as a slight swelling along the hinge line. Beak cavity moderately deep. Nacre white, iridescent on the posterior third of the shell.
Habitat: Creeks and the headwaters of large rivers in sand, mud, or fine gravel.
Status: Endangered in Illinois and Iowa. Threatened in Wisconsin.