A total of 223 taxa of Mollusca are presently known from Arkansas. The geological history and geomorphology of the region, particularly the presence of the Interior Highlands, have been responsible for the development of a diverse molluscan fauna. Thirty regionally endemic forms are included among the 107 terrestrial gastropods, 36 aquatic gastropods, 65 unionacean mussels, and 15 sphaeriacean clams
