Shell small, white, plump, with a very short, rather acute spire, and a swollen last whorl; there are four and a half closely-coiled whorls, the nucleus being sinistral and sunken; when fresh, the shell is of a translucent pinkish white, the thicker parts near the suture are more opaque and give the effect of a white band in front of the suture; the general form resembles that of A. (M) curtulus, though the shell, with the same number of whorls, is much larger, the spire less evenly dome-like, and the nucleus more sunken; suture very distinct, almost channeled; sculpture of fine, close-set, minutely punctate spiral lines, hardly visible without a lens; aperture with a well-marked anterior sulcus or canal; anterior plait on the pillar strong, prominent, the posterior plait weaker, and ending further within the aperture, but quite distinct. A very thin wash of callus on the body; outer lip thin, simple. Alt., 5.5; diam., 3.7; spire above the last whorl, 1.0 mm. (Dall.)