THE MILLIPEDE GENUS ISAPHE COOK (POLYDESMIDA, XYSTODESMIDAE)

The harpaphine xystodesmid milliped genus Isaphe, characterized by two telopodal branches and a prefemoral process that angles across the me dial face of the telopodite, comprises two species. Isaphe convexa Coo k occurs in montane forests of northern Idaho and Montana, and I. ters a (Cook) is known from riparian woodlands in canyons of the Snake, Sal mon, and Palouse river basins in southeastern Washington and west-cent ral Idaho. They are distinguished by the degree of dorsal convexity, s trong in I. convexa and weak in I. tersa, and by the length of the pre femoral process, which is long and slender and extends well beyond the caudal margin of the telopodite stem in I. convexa, and is short and broad and terminates well before the margin in I. tersa. The strong co nvexity in I. convexa results from greater expression of the dorsal cu rvature than is the case in most xystodesmids because of a lower than usual origin of the paranota, rather than from depression of the latte r. The following new synonymies are proposed: Hybaphe Cook under Isaph e Cook, H. curtipes Cook under I. tersa, and Leptodesmus (Isaphe) simp lex Chamberlin under Harpaphe haydeniana haydeniana (Wood). Modern des criptions are provided for the genus and species, and anatomical illus trations and a distribution map are presented.