Periwinkle

Periwinkle (Littorina), a genus of marine Gasteropods, represented by several species on British coasts. The commonest, Littorina littorea, is abundant between tide-marks on the rocks, and is often collected and used for food. It is boiled in its shell, extracted as eaten, and is very palatable. Periwinkles crawl about under water, but usually remain passive when left uncovered by the tide. Without water they can survive for many hours, and they are also able to endure a considerable freshening of the salt water. They feed on seaweeds, and are often useful in keeping beds of young oysters from being smothered. Periwinkles drawn up from 70 to 80 fathoms were first in 1889 used as bait for cod-fishing on the banks of Newfoundland. The edible species is oviparous, but in L. rudis, which is usually common nearer high-water mark, the young are hatched and have a hard shell before they leave the mother. These shells are apt to make this periwinkle gritty, and therefore it is not used as food. Among the structural characters of the periwinkle the substantial shell of few whorls, the closely-fitting, horny operculum, the nearly circular shell aperture without any siphon-notch are at once evident. Species of Littorina occur on almost all coasts, and there are about half a hundred in all. It should be carefully noticed that the periwinkle is often called the Wilk, Wulk, or Whelk in Scotland, but it is not nearly related to the true whelks (Purpura, Buccinum, &c.). See WHELK.