Found on seaweed at low tide on Hebrides, have only seen the empty shells before so was v happy to see one on the move!
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I have agreed Gina
This is certainly a Flat Periwinkle but (others might ask) it is obtusata or fabalis?
DO look at this http://www.ispotnature.org/node/437146 and read the comments.
THREE MARINE PROJECTS
I have uploaded an illustrated account on how to differentiate L. obtusata sensu stricto from L. fabalis at https://flic.kr/p/RcvnFf
..but I fear ian that we do not often get near enough as photographers to discern the differences. Your works does, however, inspire us to be more, well, investigative!
Lat/Lng: 56.491, -6.849
OS grid ref: NM016437
Found on seaweed at low tide