Operculum opaque white and glossy with external calcareous layer.

Shell has dark periostracum (1), not glossy except when wet (2); whitish where eroded (3). Umbilicus completely closed with calcareous pad (4). Parietal lip varies slight glaze (5) to substantial. Operculum opaque white with external calcareous layer (6).

Sublittoral, St. Lawrence Estuary, Canada, June 2016. © BY-NC C. Nozères.