Shell is black or purple above and white below, coiled, with a definite raised spire (but the shell is only about as tall as wide), no siphonal notch or canal in aperture, interior of the shell is pearly. Animal has an operculum which is thin and horny with spiral lines. Columella has two small nodes. The umbilicus is closed by a callus (picture). Shell up to 3 cm diameter. The apex is frequently heavily worn, and shell may be encrusted with coralline algae or bryozoans. Animal's foot is black on the sides. The black on the shell is due to a dark periostracum.