Dog Cockle (also known as the European Bittersweet)
Phylum: Mollusca, Class: Bivalvia, Order: Arcida, Family: Glycymerididae, Genus: Glycymeris, Species: G. glycymeris · Glycymerididae (Bittersweet clam family) · Bivalve, whole single valve, rounded to slightly sub-triangular fan shape
Species
Glycymeris glycymeris
Shell Type
Bivalve, whole single valve, rounded to slightly sub-triangular fan shape
Family
Glycymerididae (Bittersweet clam family)
Size
Approximately 1 to 1.5 inches in width, which is average for a young to mid-sized adult. Full adults of this species typically range from 1.5 to 2.5 inches.
Color & Pattern
Mottled brown, reddish-brown, and cream markings arranged in zigzag or blotchy radial patterns over a whitish base. The colors are natural and well-preserved with a subtle sheen.
Rarity
Common, frequently found washed up on European beaches after storms.
Habitat
Found in shallow marine waters, typically from the intertidal zone down to depths of about 100 meters, burrowed in coarse sand, gravel, and shelly substrates.
Geographic Range
Northeastern Atlantic Ocean, extending from the coast of Norway down through the British Isles, the Mediterranean Sea, and south to Northwest Africa.
Description
A sturdy, heavy, convex bivalve shell with distinct, fine radial ribs intersecting with growth lines to create a subtly textured surface. The margin is strongly toothed along the interior edge, and the umbo is centrally located.
Key Features
Heavy, solid construction, rounded equilateral shape, distinct radial striations, and a characteristic taxodont (row of numerous small teeth) hinge plate.
Collector Value
Low to moderate commercial value. While widely collected by beachcombers, they are too common to command high prices among serious advanced collectors, though attractive color variants are appreciated.
Condition Notes
Good condition. The exterior pattern and coloration are largely intact with minimal wear, minor fading near the edges, and no major structural fractures. Collectibility grade: Good to Fine.
Interesting Facts
Glycymeris shells have a very long fossil history and have been used by humans as ornaments and beads since prehistoric times. Their robust shells resist wave action well, making them durable sub-fossils.
Ecological Role
As filter feeders, they help clear organic particles from the water column, and they serve as an important food source for bottom-feeding fish, rays, and carnivorous gastropods.
Similar Species
Glycymeris nummaria (Pectunculus pilosus), which tends to be hairier when fresh and has slightly different geographic distributions or subtle sculpture variations.
Beach Finding Tips
Look along coarse sand and shell-gravel beaches in Western Europe and the Mediterranean, especially following rough weather or high spring tides.