The harpaphine xystodesmid milliped genus Isaphe, characterized by two telopodal branches and a prefemoral process that angles across the medial face of the telopodite, comprises two species. Isaphe convexa Cook occurs in montane forests of northern Idaho and Montana, and I. tersa (Cook) is known from riparian woodlands in canyons of the Snake, Salmon, and Palouse river basins in southeastern Washington and west-central Idaho. They are distinguished by the degree of dorsal convexity, strong in I. convexa and weak in I. tersa, and by the length of the prefemoral 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 convexity in I. convexa results from greater expression of the dorsal curvature than is the case in most xystodesmids because of a lower than usual origin of the paranota, rather than from depression of the latter. The following new synonymies are proposed: Hybaphe Cook under Isaphe Cook, H. curtipes Cook under I. tersa, and Leptodesmus (Isaphe) simplex Chamberlin under Harpaphe haydeniana haydeniana (Wood). Modern descriptions are provided for the genus and species, and anatomical illustrations and a distribution map are presented.
Timing and deformation conditions of the western Idaho shear zone, West Mountain, west-central Idaho
