Montana Field Guide

Highly variable in form. Medium-sized to large, the shell diameter ranges from 9 to 28 mm, depending on subspecies, but usually more than 15 mm (new-born young about 3 mm diameter), and from 6 to 18 mm in height but usually less than 14 mm. Typically flattened heliciform, with 4 1/3 to 5 3/4 whorls, but varies from elevated to depressed in profile; the periphery is weakly to sharply angular. Umbilicus is relatively broad and deep, the aperture ovate to rounded, lip barely thickened inside. Shell opaque and chalky, color is grayish (dead shells to pearly white), with a series of reddish-brown spiral bands, typically one on the upper surface and another just below the periphery, sometimes with one or more fainter bands below that; bands may be evident on penultimate whorl, or may be very pale or absent entirely, probably from abrasion and exposure to sunlight. Shell surface with coarse, irregular axial riblets and striae, sometimes with faint spiral sculpting as well (Hendricks 2012, Burke 2013). Internal anatomy is described by Pilsbry (1934) and (1939).

Possible subspecies: O. s. capex, O. s. fragilis and O. s. goniogyra in Idaho only; O. s. berryi and O. s. cooperi in Montana only; O. s. strigosa and O. s. depressa in both states.

Validity, status and distribution of the various subspecies need additional study. Oreohelix strigosa probably includes a multitude of full species lumped under one name; O. s. cooperi already is treated as a full species by some authors. Oreohelix strigosa berryi described originally in 1915 from specimens collected in Swimming Woman Creek Canyon of the Big Snowy Mountains in Golden Valley County.

Medium to large size, calcareous whitish to gray, somewhat flattened to moderately elevated spire, variable banding, relativley broad umbilicus, absence of refelcted lip, and surface sculpture help distinguish this from most other larger shells. Typical O. subrudis has a higher spire and smaller umbilicus, O. yavapai has a much flatter profile, broader umbilicus, and oblique and oval aperture.

Near streams, moister forested locations, and in drier sites including talus slopes and vegetated rockslides or stony ground; O. s. berryi associated with limestone. Canopy species include Douglas-fir, lodgepole pine, ponderosa pine, western redcedar, western hemlock, western larch, Engelmann spruce, rocky mountain juniper, aspen, black cottonwood, mountain maple, alder, and willow. Live animals present mostly under rocks or wood and in duff or soil accumulations; sun-bleached shells may be found on the surface (Hendricks 2012).