Illinois Natural History Survey - University of Illinois

Uniomerus tetralasmus (Say, 1831)

Pondhorn


 

Uniomerus tetralasmus, INHS 7807Uniomerus tetralasmus, INHS 7807. Mississippi River, Perry County, Missouri. 
Length: 4.0 inches (10.2 cm).

Other common namesHorn shell.

Key characters Relatively thin, smooth, elongate shell, light to dark brown, pointed, and rayless. Posterior slope with a short ridge formed by two shallow grooves on either side.

Similar species Yellow sandshellgiant floatercracking pearlymusselcylindrical papershellcreeper.

Description Shell relatively thin, elongate, and compressed to moderately inflated. Anterior end rounded, posterior end bluntly or sharply pointed. Dorsal margin straight, ventral margin straight, rarely curved. Umbos low, approximately even with the hinge line. Beak sculpture of four or five concentric ridges. Two shallow grooves present on the posterior slope, giving rise to a short ridge. Surface smooth and shiny in small shells, becoming rougher and dull in older individuals. Periostracum greenish or yellowish brown in young individuals, adults dark brown to black and rayless. Length to 5 inches (12.7 cm).

Pseudocardinal teeth small and thin; two in the left valve, one in the right. Lateral teeth relatively thin, short, and straight to slightly curved. Beak cavity shallow. Nacre white, occasionally with a tinge of salmon.Uniomerus tetralasmus distribution

Habitat Ponds, small creeks, and the headwaters of larger streams in mud or sand. (This mussel can withstand periods of desiccation and is often present in areas where few other mussels are found.)

Status Widespread but generally uncommon. May be abundant in its preferred habitat. Threatened in Ohio.


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