Common Periwinkle (alternate: Marsh Periwinkle, Grey Littorina)
Phylum: Mollusca, Class: Gastropoda, Subclass: Caenogastropoda, Order: Littorinimorpha, Family: Littorinidae, Genus: Littorina, Species: Littorina littorea · Littorinidae (Periwinkle family) · Gastropod (univalve snail); complete whole shell with a turbinate (conical-spiral) shape.
Species
Littorina littorea (Confidence: Moderate-High, typical juvenile form)
Shell Type
Gastropod (univalve snail); complete whole shell with a turbinate (conical-spiral) shape.
Family
Littorinidae (Periwinkle family)
Size
Approximately 6–8 mm in height based on comparison with human fingertips. This is a juvenile specimen, as adult periwinkles typically reach 15–30 mm (0.6–1.2 inches).
Color & Pattern
Overall brownish-grey exterior with light cream to off-white raised spiral cords (threads). The aperture interior appears dark brown to blackish with a smooth, light inner lip.
Rarity
Very Common; frequently found along intertidal shorelines and shell drift lines.
Habitat
Intertidal and shallow subtidal zones on rocky shores, stone piers, salt marshes, mudflats, and seagrass beds.
Geographic Range
Native to the northeastern Atlantic (Europe), widely introduced and established along the northwestern Atlantic (from Canada to mid-Atlantic US coastlines).
Description
A small, sturdy, turbinate gastropod shell featuring a pointed apex and strong, evenly spaced spiral ribs. The exterior shows alternate greyish-brown and lighter cream tones along the ridges. The aperture is broadly oval, with a smooth columellar margin and a dark interior.
Key Features
Distinct coarse spiral ridges encircling the whorls, pointed spire, oval aperture, thick outer lip without teeth, and compact, cone-like spiral profile.
Collector Value
Low monetary value due to extreme abundance ($0.50–$2.00 USD), but highly valued as an educational or representative specimen for regional shoreline collections.
Condition Notes
Good condition for a beach-drift specimen. Minor surface wear on the apex and outer lip margin, but the spiral sculpture and aperture integrity remain well-preserved.
Interesting Facts
Periwinkles can survive extended periods out of water by tightly sealing their aperture with a horny operculum. They are edible and have been a popular seafood delicacy in Europe for centuries.
Ecological Role
Important intertidal herbivore that grazes on algae and bio-films, keeping rock surfaces clear for other sessile organisms. Serves as a major food source for shorebirds, crabs, and fish.
Similar Species
Littorina saxatilis (Rough Periwinkle, which has variable, often coarser ridges and direct development without planktonic larvae) and Littorina obtusata (Flat Periwinkle, which has a flattened spire and smooth exterior).
Beach Finding Tips
Look in high-intertidal tide pools, attached to rocks, wooden pilings, or mixed into shell-hash drift along rocky or gravelly beaches at low tide.