Anodontoides ferussacianus (Lea, 1834)
Other common names Cylinder.
Key characters Thin shell, without teeth, fine V-shaped beak sculpture.
Description Shell thin, elongate, elliptical, and inflated in females and older males. Anterior end rounded, posterior end bluntly pointed. Ventral margin either slightly curved, straight to moderately arched, or pinched in the middle. Posterior ridge rounded, prominent, and swollen in females. Umbos small, in forward third of shell, only slightly raised above the hinge line. Beak sculpture of three or four very fine, V-shaped ridges. Shell smooth, shiny, yellowish green, green, or brown, lighter on the beaks, with fine green rays, more concentrated on the posterior half of the shell, may be absent in older shells. Length to 3 inches (7.6 cm).
Both valves without teeth. Hinge line thin and straight to slightly curved. Beak cavity shallow. Nacre silvery or bluish white and iridescent posteriorly.
Habitat Small creeks and the headwaters of larger streams in mud and sand.
Status Widespread and locally abundant. Endangered in Missouri. Threatened in Iowa.