Margined Ramshorn - Planorbis planorbis
Shell size: 9-18mm, height: 2.5-4 mm. A rather thick and strong shell. It is not glossy and it has a paler keel towards the periphery, past the mid-line but not right at the edge. There are 5 or 6 whorls which increase regularly in size. The mouth may be slightly expanded and sometimes bears a narrow rib inside.
The main confusion is likely to be with the Keeled Ramshorn, Planorbis carinatus, which also has a keel. They can be distinguished by the position of the keel and the profile of the shell joining the keel. P. planorbis is flattened on one side with the keel very much at the edge with a rounded shell joining this keel. In P. carinatus the keel is off-centre but not right at one side with the shell more sloping at an angle to reach this keel.
Ponds, ditches, and in quiet slow flowing canals and rivers, usually in the shallower parts amongst the water weeds.
All year round.
It is found in most counties of England, and many in Ireland, but is recorded only infrequently from Wales and Scotland.
Common in Leicestershire and Rutland.
Leicestershire & Rutland Map
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