Utterbackia (=Anodonta) imbecillis (Say, 1829)
Other common names Paper floater, papershell.
Key characters Relatively small thin shell, flattened beaks, double-looped beak sculpture, without teeth.
Description Shell elongate, oblong, compressed in young, becoming inflated in older shells. Shell extremely thin, transparent in young individuals. Anterior end rounded, posterior end somewhat pointed. Ventral margin straight to moderately rounded. Umbos well forward, flattened, not rising above the hinge line. Beak sculpture double-looped, with five or six fine, wavy ridges. Shell smooth, shiny, light yellow in young and on the umbo of adults, rest of shell brownish green, occasionally with fine green rays. Length to 4 inches (10.2 cm).
Both valves without teeth, hinge line straight and thin. Beak cavities shallow or absent. Nacre white or bluish white and iridescent posteriorly.
Habitat Ponds, lakes, and sluggish mud-bottomed pools of creeks and rivers.
Status Widespread and locally abundant.