H/L 63%, high shell developed near HW in Mersey Estuary where fluctuating salinity and extended exposure to desiccation and rain induce prolonged clamping down so contracted mantle creates shell with constricted diameter. No limpets on lower levels of Mersey shore as turbid water and sediment on hard surfaces obstruct growth of algal food. Image 59Pv shows algal growth near HW where lack of competition promotes large size, L. 45 mm. Apex 43% of L. from anterior; nearer to centre (50%) than others examined. August 2017.