Montana Field Guide

Highly variable in form. Medium-sized to large, the diameter ranges from 11 to 23 mm, but usually more than 15 mm (new-born young about 2 or 3 mm diameter), and from 8 to 18 mm in height, depending on subspecies and local conditions. Typically heliciform to almost bee-hive shaped, with up to 6 whorls; the periphery is weakly angular. Umbilicus is narrow and deep, the aperture ovate to rounded, slightly thickened inside. Shell opaque and chalky, color pale gray to brownish (dead shells may be 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. Shell surface with coarse irregular axial riblets and striae, sometimes with faint spiral sculpting (Hendricks 2012, Burke 2013). Internal anatomy is described by Pilsbry (1939).

Subspecies: O. s. subrudis, O. s. apiarium, O. s. limitaris; O. s. apiarium and O. s. limitaris may be synonyms.

Medium to large size, calcareous whitish to gray (some may be brownish), moderately elevated spire (sometimes almost bee-hive shape), variable banding, relativley narrow umbilicus, absence of refelcted lip, and surface sculpture help distinguish this from most other larger shells. Typical O. strigosa has a lower spire and larger umbilicus, O. yavapai has a much flatter profile, broader umbilicus, an obvious keel, and oblique and oval aperture.

Often in relatively moist sites, along stream courses and near seeps or springs, sometimes in talus slopes. Canopy species include western red-cedar, western hemlock, Douglas-fir, Engelmann spruce, ponderosa pine, limber pine, black cottonwood, aspen, paper birch, alder, willow, and rocky mountain juniper. Live animals present mostly in leaf litter, and under downed wood, rocks, and in duff or soil accumulations under wood and rocks; sun-bleached shells may be found on the surface (Berry 1919, Beetle 1987, Hendricks 2012).