While, as Mr. Fall points out, the species of this group are rather closely allied, there seems to be a number of forms not yet described. Mr. W. J. Brown has recently described two species from British Columbia and the three treated in this paper seem clearly distinct.

The distinctions among the species are rather difficult to define, though, with the exception of certain forns of vilis and planiusculus, the differences may be seen clearly when secimens are at hand.