2 NEW CANADIAN SPECIES OF THE GENUS TRICORYTHODES ULMER, WITH ADDITIONAL STUDIES ON OTHER NORTH-AMERICAN SPECIES (INSECTA, EPHEMEROPTERA, LEPTOHYPHIDAE)

Two new mayfly species (Tricorythodes mosequs n.sp. and T. cobbi n.sp.) are described from the Assiniboine River, Manitoba, Canada. Taxonomic knowledge of the North American species of the genus Tricorythodes is summarized. The type material of T. stygiatus McDunnough, T. atratus (McDunnough), and T. peridius Burks was studied and additional characteristics of these species are described. New drawings of the genitalia of these species are presented. Tricorythodes peridius and T. atratus are considered to be junior synonyms of T. allectus (Needham). A key to the imagines of Tricorythodes in Canada is included.