Toxolasma lividus (Rafinesque, 1831)
Other common names: Little purple.
Key characters: A small, slightly elongate shell, dark brown, pointed or truncated on the posterior end, with a purple nacre.
Description: Shell small, rounded to somewhat oblong, relatively solid, and inflated. Anterior end rounded, posterior end bluntly pointed (males) or truncated (females). Umbos inflated and slightly elevated above the hinge line. Beak sculpture of three or four heavy bars. Periostracum tan or dark green to dark brown, becoming black in older shells. Length to 1 inch (2.5,cm).
Pseudocardinal teeth well developed, elevated and serrated; two in the left valve, one in the right. Lateral teeth straight to slightly curved; two in the left valve, one in the right. Beak cavity variable from very shallow to moderately deep. Nacre purple, usually lighter near the ventral margin, and iridescent.
Habitat: Lakes and small to medium streams in gravel.
Status: Federal Candidate (Category 2). Endangered in Illinois, Michigan, and Ohio. Watch List in Missouri.