03 Potamopyrgus antipodarum

03 Potamopyrgus antipodarum

Occasional form with keel bearing periostracal bristles. Encrustation on shell and bristles is usually black; orange colour perhaps due to oxidization of iron content.
Shell height 4 mm. On stonework of bridge.  Llanfihangel (Ynys), Wales. September 2012.