The Illinois River is in the Ozark region of northwestern Arkansas and eastern Oklahoma. A survey of the Illinois River in Arkansas produced nine species and one morphological subspecies of gastropods, three species of sphaeriid clams, and 23 species of unionid mussels. Museum records resulted in another two species and an ecophenotype of the Unionidae. This represents the first published survey of molluscan species from the Illinois River in Arkansas.
Gordon, M. E.; Brown, Arthur V.; and Kraemer, L. Russert
"Mollusca of the Illinois River, Arkansas,"
Journal of the Arkansas Academy of Science: Vol. 33
, Article 14.
Available at: http://scholarworks.uark.edu/jaas/vol33/iss1/14