Greater Ramshorn Snail

Planorbarius corneus corneus or greater ramshorn snail is the other gastropod in our pond. I pinched a couple from a lovely pond in a local house we were visiting and put them in mine soon after I made it a couple of years ago. I thought they'd perished as I hadn't seen any until the other week. 
The pond, as all nature garden writers tell you, has been absolutely amazing for wildlife: loads of damsel and dragonflies. Toads, frogs and newts. Hoverflies.