In zoology, any of some 80 species (family Littorinidae) of widely distributed, chiefly herbivorous shore snails
. Periwinkles are usually found on rocks, stones, or pilings between high- and low-tide marks. The common periwinkle (Littorina littorea
), the largest northern species, may grow to 1.5 in. (4 cm) long. It is usually dark gray and has a solid spiral shell. Introduced into North America circa
1857, it is now common on Atlantic coasts. All periwinkle species are a favourite food of many shorebirds.
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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.