Venustaconcha ellipsiformis (Conrad, 1836)

Venustaconcha ellipsiformis, INHS 4137. Rock River, Illinois. Length: 2.9 inches (7.4 cm).

Other common names: None.

Key characters: Small, elongate shell, relatively thick for its size, with short, heavy lateral teeth and numerous wavy green rays on the posterior half of the shell.

Similar species: Rayed bean, rainbowmucketspike.

Description: Shell small, solid, elliptical, and compressed. Anterior end rounded, posterior end bluntly pointed. Ventral margin straight to slightly curved. Umbos only slightly elevated above the hinge line. Beak sculpture of three or four very fine, double-looped ridges. Shell usually smooth, with a few wrinkles or folds on the posterior half in older shells. Periostracum green or greenish yellow with numerous dark green rays, becoming wavy on the posterior half of the shell. Length to 3 inches (7.6 cm).

Ellipse distribution map 1992

Pseudocardinal teeth triangular, heavy, roughened, and divergent; two in the left valve, one in the right (occasionally with a thin, ridgelike tooth in front). Lateral teeth relatively short, thick, and straight to slightly curved. Beak cavity shallow. Nacre white, iridescent posteriorly.

Habitat: Small to medium streams in gravel or mixed sand and gravel.

Status: Uncommon. Extirpated from Ohio. Threatened in Iowa and Wisconsin. Species of Special Concern in Illinois and Indiana.

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