Costal ribs on largest three whorls. Ribs cease on the final part of the body whorl (1) but are prominent above the periphery of the apertural face (2).
About 20 spiral lines of pits retaining brown periostracum form a rectangular matrix (3).
Protoconch retains constant size at all growth stages, so appears relatively larger on small, young shells (4). Rim of aperture (5) and area adjacent to it (6) stained lilac.
Oval aperture is angled where columellar lip joins the parietal lip (7).
Shell height 3.9 mm. North Wales, March 2015.