Opercular lobe of P. sarsii, seen through transparent operculum, has a pale posterior (1) with small dark mark and a black anterior (2). Most of opercular disc is white (3). Umbilical groove (4) between slightly reflected columellar lip and body whorl. Costae of body whorl terminate at periphery (5), leaving base smooth. In apertural view six rounded, widely spaced costae (6-6) visible on body whorl, and six visible in abapertural view (7). Abapertural edge of costa apparently raised and steep (8) and adapertural edge apparently low and gently inclined (9). Colour mainly confined to grooves. No tiny apical purple spot (10). Roskilde Fjord, Denmark, September 2015. Leg. & © K. Jensen. Coll. National Museum Wales.