Leptodea fragilis (Rafinesque, 1820)
Leptodea fragilis, INHS 8019. Henderson Creek, Henderson County, Illinois.
Other common names Papershell, cottonmouth.
Key characters Thin, fragile, elongate shell, yellow or yellowish green with faint green rays, rounded posterior end, pinkish white and iridescent nacre.
Description Shell somewhat oblong, thin, and compressed. Anterior end rounded, posterior end rounded in males and broadly expanded in females. Dorsal wing present in young shells, becoming greatly reduced or absent in older individuals. Umbos flattened and only slightly elevated above the hinge line. Beak sculpture of three or four faint, double-looped bars. Shell smooth, shiny to dull, yellow or yellowish green, usually with numerous light green, indistinct rays; some rayless. Length to 6 inches (15.2 cm).
Pseudocardinal teeth small, reduced to a thin ridge in small shells, becoming a thickened swelling in older shells; two in the left valve, one in the right. Lateral teeth long, thin, and compressed; two in the left valve, one in the right. Beak cavity shallow or absent. Nacre pinkish white or pink and highly iridescent.
Habitat Streams of all sizes in mud, sand, or gravel.
Status Widespread and common.