Peterson counsels you to wash the periwinkles in a colander under cold water as soon as you get them home, checking to see that their little doors are securely shut (a sign that they're still alive).
"Periwinkle. Littorina littorea, an edible mollusc living in a small single shell...widely distributed on both sides of the N. Atlantic.
Periwinkles - These small relatives of the whelk are "Littorina littorea". Popular in Europe but not in US. Northern (New England) "winkles" are a different species from those found in the Gulf of Mexico.
Plateau de fruits de mer (Fr.): seafood platter combining raw and cooked shell-fish; usually includes oysters, clams, mussels, langoustines, periwinkles, whelks, crabs, and tiny shrimp.
See also: Cooking, Periwinkle, Water, Sauce, Roast