Common Periwinkle

Thank you very much Mollie, and Loannis for the ID! I loved the text as well, Loannis! Mollie, I sink Loannis is correct and I will be shore to add the correct ID. ;-)

Probably Common periwinkle, Littorina littorea:
http://en.wikipedia.org/wiki/Littorina_l...
but look also at rough periwinkle, Littorina saxatilis:
http://en.wikipedia.org/wiki/Littorina_s...
And the text here:
http://www.geog.mcgill.ca/climatechange/...

Maby it's sea snail. Not shore what kind