Ligumia subrostrata (Say, 1831)
Ligumia subrostrata, INHS 5569. Skillet Fork, Marion County, Illinois.
Other common names Western pondmussel, common pondmussel, western sand shell.
Key characters Small, elongate shell, pointed or truncated on the posterior end, with thin teeth, beak with numerous wavy ridges if not entirely eroded, yellowish brown with green rays.
Description Shell relatively small, thin, elongate, and compressed. Anterior end rounded, posterior end pointed in males, saber-shaped in females. Dorsal and ventral margins straight. Umbos slightly elevated above the hinge line. Beak sculpture of six to eight distinct, wavy ridges but often eroded and not visible. Shell smooth, dull, greenish yellow, becoming darker brown to black in older shells. Dark green rays present but faint in some specimens. Length to 3 inches (7.6 cm).
Pseudocardinal teeth thin, compressed, and divergent; two in the left valve, one in the right. Lateral teeth long, thin, and straight; two in the left valve, one in the right. Beak cavity relatively shallow. Nacre white and highly iridescent posteriorly.
Habitat Small creeks or ponds in mud or sand.
Status May be common in its preferred habitat. Extirpated from Ohio.