The mollusk fauna of the Great Lakes is not well known, and the sphaeriid clams have never been recorded. Although ignored until recently, specific identification is necessary when studying food relationships, parasitology, and distribution. List of sphaeriids from each of the Great Lakes reveal that Lake Superior has 6 species; Lake Michigan, 20; Lake Huron, 20; Lake Erie, 14; Lake Ontario, 26 species. Among these sphaeriids, some species are more common than others, and occurrence varies with depth of water and type of substrate.