The Chicago Academy of Sciences’ malacology collection consists of freshwater, marine, and terrestrial Mollusca, as well as specimens representing Echinodermata, Porifera, Brachiopoda, and Cnidaria. It is the third largest in the state of Illinois with approximately 15,000 specimens, split mainly between gastropods and bivalves. Many specimens are associated with Academy collectors, e.g. William Stimpson (1832-1872) or Frank C. Baker (1867-1942). Other major collectors include Elizabeth Emerson Atwater, William Wirt Calkins, Ruthven Deane, J. H. Handwerk, R. L. Lea, Howard N. Lyon, E. N. King, J. W. Velie, Frank Morley Woodruff, and Mrs. E. C. Wiswall. The collection consists mainly of North American varieties of mollusk, with a strong regional focus on the Midwest. Approximately 24% of domestic lots originated in Illinois. Academy expeditions in the late 1800s and early 1900s contributed a significant number of specimens from California and Florida, while a number of specimens collected by William Stimpson came from the eastern coast of the United States. Additional specimens originated in Bermuda, the Bahamas, Mexico, China, Indonesia, and Japan. Collection includes 7 holotypes and 50 syntypes, and specimens were primarily collected pre-1945.