Truncilla donaciformis (Lea, 1828)
Other common names: Little pocketbook.
Key characters: Small, elongate shell, greenish yellow, with zigzag markings.
Description: Shell small, elongate, somewhat oblong, relatively thin, and compressed to moderately inflated. Anterior end rounded, posterior end pointed, ventral margin smoothly rounded. Umbos full, centrally located, and slightly elevated above the hinge line. Beak sculpture of five or six double-looped bars. Periostracum variable from yellow to greenish brown, with numerous dark green rays made up of many smaller broken, V-shaped or zigzag lines. Length to 2 inches (5.1 cm).
Pseudocardinal teeth small, roughened, and elevated; two in the left valve, one in the right. Lateral teeth thin, relatively long, and straight to slightly curved. Beak cavity moderately shallow. Nacre white, iridescent posteriorly.
Habitat: Large rivers or the lower reaches of medium-sized streams in sand or gravel.
Status: Widespread and common throughout most of its range. Threatened in Ohio.