Identification Needed for Seashells found along the Gulf of Biscay

[dave r]

Hi Milz, they are not shells as such but opercula. This is like a 'trap door' that the animal uses to close the aperture after it has withdrawn into its shell so sealing itself in away from predators. Not all shells have them and some are soft and sort of 'plasticy' but these are from shells of the family Turbinidae which always have a hard shelly operculum. Some species have them brightly coloured and some call them 'cat's eyes', if you google up Turbo petholatus you will see them. I suspect yours are from the species Bolma rugosa which lives in the Mediterranean and adjacent seas.
Hope this helps,
Dave
P.S. are you in the U.K.?