Material was obtained from sections of the Hamilton Group in the northern Southern Peninsula of Michigan; near Silica, Lucas County, Ohio; near Sandusky, Erie County, Ohio; the western half of New York; and Middlesex and Lambton Counties, Ontario. Six genera, 25 species, ten subspecies, and one variety were studied in regard to their regional and stratigraphic relationships. Seven species, three subspecies, and the variety are new. Nine species and two genera (Lucasella Stewart, 1936, and Spinovina Coryell and Malkin, 1936) are considered to be synonyms. Middle Devonian specimens formerly assigned to the genus Burlella Coryell and Booth are assigned to the genus Quasillites. Known geographic ranges of many species are extended.