Translucent yellow-horn shell colour is often hidden by dark encrustation, except on the most recent whorl of still growing juveniles and sub-adults.
Head has long mobile tentacles; translucent grey, darkest dorsally except, often, for fine faint pale medial line (visible on left tentacle in image). No white marks on tentacles except a few white dots in front of eye.
Shell height 3.8 mm. Freshwater pool, Dee Estuary, Cheshire. September 2011.