Illinois Natural History Survey - University of Illinois

Villosa fabalis (Lea, 1831)

Rayed bean


 

Villosa fabalis, INHS 4885Villosa fabalis, INHS 4885. Salt Fork Vermilion River, Champaign County, Illinois. 
Length: 1.1 inches (2.8 cm) for male (top), 1.0 inch (2.5 cm) for female (bottom).

Other common names Bean shell.

Key characters Very small and solid shell with numerous wavy green lines on the outer surface and teeth that are unusually heavy and thick for their size.

Similar species Ellipse, rainbow.Villosa fabalis distribution

Description Shell small (usually under 1 inch [2.5 cm]), elongate, thick, solid, and moderately inflated. Anterior end rounded, posterior end rounded to bluntly pointed. Dorsal margin straight, ventral margin straight to slightly curved. Umbos slightly elevated above the hinge line. Beak sculpture, if visible, of two or three heavy ridges. Periostracum green, yellowish green, or brown with numerous wavy green rays. Length to 1.5 inches (3.8 cm).

Pseudocardinal teeth triangular, relatively heavy and large; two in the left valve, one in the right. Lateral teeth short, heavy; two in the left valve, one in the right. Beak cavity shallow. Nacre white or bluish white, iridescent posteriorly.

Habitat Lakes and small to large streams in sand or gravel.

Status Federal Candidate (Category 2). Endangered in Illinois, Michigan, and Ohio. Species of Special Concern in Indiana.


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