Common Periwinkle (also known as Littorina)
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Littorinidae, Genus: Littorina, Species: Littorina littorea · Littorinidae (Periwinkle family) · Gastropod (spiral univalve, whole shell)
Species
Littorina littorea
Shell Type
Gastropod (spiral univalve, whole shell)
Family
Littorinidae (Periwinkle family)
Size
Approximately 0.75 inches (20 mm) in length, which is average for an adult specimen of this species. Adults typically range from 0.5 to 1.2 inches.
Color & Pattern
Dull brownish-grey to dark olive-brown exterior with faint, subtle darker spiral bands. The colors appear slightly weathered and natural, with no extreme sun-bleaching. The interior aperture is dark brown to purplish.
Rarity
Very Common, frequently found washed ashore or clinging to rocks in its native and introduced intertidal zones.
Habitat
Found primarily in the intertidal zone, attached to rocky shores, piers, and seaweeds, grazing on microalgae. It is a robust marine and brackish-tolerant species.
Geographic Range
Native to the rocky shores of the North Atlantic, including northwestern Europe, and introduced to northeastern North America from Canada down to the Mid-Atlantic states.
Description
A sturdy, conical shell with a moderately elevated spire consisting of about six convex whorls. The surface is relatively smooth with faint fine growth lines. The aperture is rounded-oval with a simple outer lip and a small columella.
Key Features
Conical shape, smooth to faintly banded brownish exterior, rounded aperture without a siphonal canal, and solid construction adapted to wave action.
Collector Value
Low monetary value due to extreme abundance, but a staple species for beginner shell collections and educational displays. Typically worth only a few cents to a dollar.
Condition Notes
Good condition with a mostly intact spire and lip, though showing slight signs of natural weathering and minor surface wear consistent with beach or intertidal collection. Collector grade: Good.
Interesting Facts
The common periwinkle was introduced to North America from Europe in the 19th century and has since become one of the most dominant intertidal grazers. They are edible and commonly harvested for food in parts of Europe.
Ecological Role
Acts as an important herbivore in rocky shore ecosystems, controlling algal growth and serving as a food source for shorebirds, crabs, and fish. Generally not heavily regulated due to high population numbers.
Similar Species
Rough Periwinkle (Littorina saxatilis) and Smooth Periwinkle (Littorina obtusata), which can be distinguished by differences in spire height, overall shell proportions, and specific habitat preferences.
Beach Finding Tips
Search rocky intertidal zones, tide pools, and areas with abundant seaweed during low tide. Look closely among crevices and under rocks where they cling.