New Record for the Freshwater SnailLithasia geniculata(Gastropoda: Pleuroceridae) in the Ohio River, IL, with Comments on Potential Threats to the Population

We report on a recently discovered population of the freshwater snail Lithasia geniculata (Ornate Rocksnail) (Gastropoda: Pleuroceridae) from the Ohio River, IL, the first documented occurrence for this species outside the Tennessee and Cumberland river basins. We collected 14 individuals on 26–27 August 2008 from the Ohio River, near Mound City, Pulaski County, IL. All of the specimens collected were discovered on an exposed shoal after the river dropped ≈0,5 min a 24-hr period and had several (7–33) Dreissena polymorpha (Zebra Mussel) attached to their shells.