1. Potamopyrgus antipodarum. Shell heights 4.5mm to 1.1mm. All encrusted, except most recent whorl of growing juveniles. Top left specimen is keeled. From slowly flowing freshwater pool at top of salting, Dee Estuary, Cheshire.
2. Potamopyrgus antipodarum. Shell heights 4.5mm to 1.1mm. All encrusted, except most recent whorl of growing juveniles. Top left specimen is keeled. From slowly flowing freshwater pool at top of salting, Dee Estuary, Cheshire.

Potamopyrgus antipodarum. Shell heights 4.5mm to 1.1mm. All encrusted, except most recent whorl of growing juveniles. Top left specimen is keeled. From slowly flowing freshwater pool at top of salting, Dee Estuary, Cheshire.