Common periwinkle - Wikipedia
Periwinkle | Gastropod, Intertidal, Mollusk | Britannica
Common Periwinkle | New England Wildlife Center
Littorina littorea - Smithsonian Institution
Periwinkles Fast Facts - U.S. National Park Service
Common Periwinkle (Littorina littorea) - iNaturalist
Littorinidae - Wikipedia
Littorina littorea (common periwinkle) | CABI Compendium
The Common Periwinkle Profile - ThoughtCo
Common periwinkle (Littorina littorea) - MarLIN - The Marine Life ...