Shell has dark periostracum (1); whitish where eroded (2). Distinct sutures (3) give the short spire a stepped profile (4); often eroded. Umbilicus completely closed with calcareous pad (5). Palatal (outer) lip meets the parietal lip at c. 90° (6). Operculum opaque white with external calcareous layer (7).

Height 23 mm, sublittoral, St. Lawrence Estuary, Canada, August 2007. © BY-NC C. Nozères.