Illinois Natural History Survey - University of Illinois

Ligumia recta (Lamarck, 1819)

Black sandshell

Ligumia recta, INHS 11769 and 11722. Mississippi River, Rock Island County, Illinois. 
Length: 4.6 inches (11.7 cm) for male (top), 4.8 inches (12.2 cm) for female (bottom).

Other common names Black sand mussel, long John, honest John, sow's ear, lady's slipper.

Key charactersElongate shell, pointed on the posterior end, smooth surface, usually dark brown to black, with a pinkish or purple nacre.

Similar species Spike, spectaclecase, yellow sandshell.

Description Shell elongate, solid, and moderately compressed. Anterior end rounded, posterior end pointed in males, saber-shaped in females. Dorsal margin straight, ventral margin straight to curved. Umbos low, only slightly elevated above the hinge line. Beak sculpture, if visible, of two or three indistinct, double-looped bars. Shell smooth and shiny, dark green, brown, or black, with green rays visible on some individuals. Length to 8 inches (20.3 cm).

Pseudocardinal teeth triangular, serrated, and divergent; two in the left valve, one in the right, occasionally with a small tooth anteriorly. Lateral teeth long, moderately thin, and straight. Beak cavity shallow. Nacre variable from white, pink, and salmon to deep purple, iridescent posteriorly.

Habitat Medium to large rivers in riffles or raceways in gravel or firm sand.

Status Widely distributed but uncommon in much of the Midwest. Threatened in Ohio.

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