Distribution of pleurocerids (Gastropoda) of Illinois

Freshwater mollusks are among the most rapidly declining groups of organisms on Earth. Several species of aquatic gastropods, especially those in the family Pleuroceridae, are rare globally, but not much was known about their distribution and status in Illinois. We inspected museum collection holdings, conducted literature reviews on Illinois mollusks, and sampled throughout the state to obtain data on distribution and abundance of the pleurocerid fauna with an emphasis on declining species. Eleven species of pleurocerids are known from Illinois. We collected eight species live during our three-year study, including the first collection of Lithasia geniculata in the state. We failed to find three species, one of which (Leptoxistrilineata) is believed to be extinct. In addition to the currently listed Lithasia obovata, we feel Leptoxis praerosa and L. geniculata should be listed as endangered at the state because of their limited distribution and small population size.