Flat Periwinkle, Smooth Periwinkle
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Littorinidae, Genus: Littorina, Species: L. fabalis · Littorinidae (Periwinkle family) · Gastropod (univalve); Spiral/Globose shape with a flattened spire. Consists of a whole shell.
Species
Littorina fabalis (formerly Littorina mariae)
Shell Type
Gastropod (univalve); Spiral/Globose shape with a flattened spire. Consists of a whole shell.
Family
Littorinidae (Periwinkle family)
Size
Approximately 12-15mm in diameter. This is within the average adult size range of 10-20mm for this species.
Color & Pattern
Highly variable; this specimen shows a beautiful mottled olive-grey and purple-brown base with distinct yellowish radial bands near the spire. The apex (tip) is a contrasting orange-brown. The colors appear natural but slightly weathered by the tide.
Rarity
Common; frequently found on rocky beaches and amongst seaweed, though their small size and camouflage make them easy to overlook.
Habitat
Intertidal zone, specifically found clinging to brown seaweeds like Fucus serratus (Saw Wrack) in rocky shore environments. Marine species.
Geographic Range
Northeastern Atlantic coasts, including the British Isles, Scandinavia, and down to the Iberian Peninsula. Common in Troon and the Firth of Clyde.
Description
A small, robust, globose gastropod characterized by its very low, flattened spire and large body whorl. The surface is relatively smooth with very fine growth lines. The aperture is large and rounded, designed to accommodate a muscular foot for gripping rocks and kelp.
Key Features
Flattened spire that does not protrude significantly (unlike the Common Periwinkle), globose body whorl, smooth texture, and strong association with brown seaweed habitats.
Collector Value
Low financial value but high interest for 'color series' collectors. Enthusiasts often collect 'sets' of this species to show the incredible range of color morphs (yellow, orange, green, brown, striped).
Condition Notes
Good/Fair. The shell is largely intact, but the outer lip appears slightly chipped or eroded. The color is well-preserved, and the apex shows minimal wear, which is excellent for a beach-found specimen.
Interesting Facts
Unlike many other snails, Flat Periwinkles do not have a planktonic larval stage; they lay jelly-like egg masses directly onto seaweed fronds, and the young emerge as fully formed miniature snails. Their color often mimics the specific species of seaweed they live on to avoid bird predation.
Ecological Role
Primary consumer; they graze on the epiphytic algae and micro-organisms growing on the surface of large seaweeds. They serve as a vital food source for shorebirds and crabs.
Similar Species
Littorina obtusata (Flat Periwinkle) - extremely similar, often requires dissection or microscopic examination of the penis/oviduct to distinguish; Littorina littorea (Common Periwinkle) which has a much more pointed spire.
Beach Finding Tips
Search amongst the 'wrack line' or move fresh kelp and seaweed (specifically Fucus) on rocky outcrops during low tide. They are most easily spotted when the tide is out and they are inactive.
Notes
Troon Scotland