The common periwinkle or winkle (Littorina littorea) is a species of small edible whelk or sea snail, a marine gastropod mollusk with gills and an operculum, and is classified within the family Littorinidae, the periwinkles. This is a robust intertidal species with a dark and sometimes banded shell. It is native to the rocky shores of the northeastern and introduced to the northwestern Atlantic Ocean.
This species appears in prehistoric shellfish middens throughout Europe and is believed to have been an important source of food since at least 7500 B.C.E. in Scotland. Periwinkles are usually picked off the rocks by hand or caught in a drag from a boat. They are mostly eaten in the coastal areas of Scotland, England, Wales, and Ireland, where they are commonly referred to as winkles or in some areas buckies, willicks, or wilks.
Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of mollusks, crustaceans, and echinoderms.
Although most kinds of shellfish are harvested from saltwater environments, some are found in freshwater. Shellfish are among the most common food allergens.