Wavy Cockle (also known as the Frilled Cockle or Giant Pacific Cockle)
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Cardiidae, Genus: Clinocardium, Species: Clinocardium nuttallii · Cardiidae (Cockle family) · Bivalve (two-shelled), whole shell valve, fan shape
Species
Keenmardiastra substriata or more accurately Clinocardium nuttallii
Shell Type
Bivalve (two-shelled), whole shell valve, fan shape
Family
Cardiidae (Cockle family)
Size
Approximately 2 to 2.5 inches in width, which is a medium-sized specimen. Adults of this species typically range from 2 to 4 inches.
Color & Pattern
Pale off-white to creamy base color with subtle hints of light brown and grayish-blue tinges near the margins, showing natural weathering. The interior exhibits a matching off-white tone with a hint of purple near the hinge plate.
Rarity
Common
Habitat
Found in marine environments, specifically shallow subtidal zones and intertidal mudflats or sandy substrates, living buried just beneath the surface.
Geographic Range
Pacific coast of North America, ranging from Alaska down to Southern California, including San Diego.
Description
A robust, heart-shaped bivalve valve characterized by numerous prominent, raised radial ribs intersecting with fine concentric growth lines. The margin is deeply crenulated, creating a distinct interlocking edge when the two valves are joined. The texture is rough and tactile.
Key Features
Prominent radial ribs numbering around 30 to 35, a slightly asymmetrical oval-fan shape, and a deeply scalloped, wavy outer margin.
Collector Value
Low to moderate commercial value; very common in souvenir shops and beachcombing collections along the West Coast, usually valued as a modest educational or decorative piece.
Condition Notes
Good condition with minor natural weathering, intact structural integrity, well-preserved radial ribs, and no major cracks or deep boring holes. Collectibility grade: Good.
Interesting Facts
Cockles are capable of using their muscular, hatchet-shaped foot to leap or dig rapidly into the sand to escape predators like sea stars and carnivorous snails.
Ecological Role
Serves as an important prey item for shorebirds, sea otters, and bottom-feeding fish; acts as a biological filter feeder helping to maintain water quality in coastal ecosystems.
Similar Species
Other Pacific cockles such as the Basket Cockle (Clinocardium nuttallii variants), which can be differentiated primarily by rib count and subtle shell proportions.
Beach Finding Tips
Look along Pacific Northwest and Californian sandy beaches and mudflats at low tide, particularly after winter storms when offshore bars shift and wash up intact valves.
Notes
San Diego