Montana Field Guide

A very small shell, to 1.8 mm diameter and 1.2 mm in height, flattened heliciform with a moderately-raised spire, with up to 4 1/4 whorls. Shell is translucent yellowish-brown, with a series of small closely-spaced axial riblets on both surfaces; periphery rounded. The aperture is crescent shaped, broader than high; umbilicus is somewhat narrow and deep, about 1/4 the shell diameter. The body is short and barely visible beyond the shell when crawling (Hendricks 2012, Burke 2013).

The spots are very small, yellowish brown shells (less than 3.0 mm diameter) with 4.0 to 4.25 whorls, which separates them from other species. Species of Pristiloma are more tightly coiled with more whorls, slightly larger in diameter with a narrow to absent umbilicus, and lack riblets. Punctum minutissimum is flatter in profile (lower conic) with a wider umbillicus than P. randolphi though similar in diameter, P. californicum is similar in shape to P. randolphi but larger with more solid riblets, Paralaoma caputspinulae is larger still (to > 2.0 mm diameter) with rather high cuticular riblets visible under magnification but with a flatter profile like P. californicum.

Mesic mixed conifer forest. Canopy species include western redcedar, western hemlock, Engelmann spruce, subalpine fir, black cottonwood, western larch and lodgepole pine, secondary canopy includes alder, dogwood and mountain maple. Found under woody debris in leaf litter and duff in moist sites (Berry 1919, Hendricks 2012).