I think all the shells are the same shape but there are different colours, does this change with what they feed on or genetic?
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I think these are Rough periwinkles, which are the Littorina saxatilis group. The taxonomy of rough winkles was a minefield from the early 1960s and field biologists generally lumped them all together. Now the accepted wisdom can be seen in Crothers key for the larger species of marine molluscs that live on rocky shores around the British Isles, including the Littorina species. Have a look and see what you think.
Lat/Lng: 54.303, -0.409
OS grid ref: TA036908