Except for one species described by Cresson as Cteniscus californicus, but apparently referable to this genus, all the known American species occur in Canada. A study of the material contained in the National Collection has revealed several species which appear to be new. Descriptions of these are given below together with notes on the previously described species and a key is provided for the separation of all species except californicus. According to the original description of californicus it differs from the species here treated in having the mesoscutum prominently marked with two reddish longitudinal stripes.