Checkered Cockle, Egg Cockle
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Cardiidae, Genus: Laevicardium, Species: Laevicardium substriatum · Cardiidae (Cockle family) · Bivalve (clams/two-shelled); this specimen is a single valve (half-shell) with a fan-like, inflated shape.
Species
Laevicardium substriatum or Americardia biangulata (likely the former given San Diego location)
Shell Type
Bivalve (clams/two-shelled); this specimen is a single valve (half-shell) with a fan-like, inflated shape.
Family
Cardiidae (Cockle family)
Size
Approximately 0.75 to 1 inch (20-25mm). This is a typical adult size for this species, which usually maxes out around 1.2 inches.
Color & Pattern
Creamy white to light beige base with subtle, faint yellowish-brown mottling. The interior is likely white or tinted with yellow. The exterior appears slightly weathered and sun-bleached, which is common for beach-found specimens in California.
Rarity
Common; frequently found on the beaches of San Diego and Coronado, especially after winter storms or high tides.
Habitat
Marine; typically found in shallow subtidal waters, burial in sandy substrates or mud flats ranging from the intertidal zone to depths of 50 meters.
Geographic Range
Eastern Pacific coastline, ranging from Mugu Lagoon in California down through the Gulf of California to the coast of Peru.
Description
This is a small, sturdy, heart-shaped bivalve when both valves are joined. It features a moderately inflated shell with numerous fine, radiating ribs. The texture is relatively smooth compared to 'true' cockles, with a slightly glossy feel if the periostracum were present. Its shape is sub-ovate with a prominent beak (umbo) near the center.
Key Features
Rounded, inflated valves; fine radiating ribs that are mostly visible toward the margins; lacking the heavy, prickly spines found on larger cockle species; symmetrical fan shape.
Collector Value
Minimal monetary value ($1-$3) but high sentimental value for beachcombers. They are common in southern California shell craft and beginner collections due to their pleasing, symmetrical heart shape.
Condition Notes
Good condition for a beach find. The valve is intact without significant chips or predator boring holes. It shows some natural erosion of the fine surface details and slight color loss due to sun exposure. Grade: Fine.
Interesting Facts
Cockles are known as 'jumping clams' because they have a powerful, L-shaped muscular foot that they can use to push off the sandy bottom to escape predators like sea stars. Locally in Coronado, they are part of a delicate sandy-bottom ecosystem that supports various shorebirds.
Ecological Role
Suspension feeders that filter plankton and organic detritus from the water. They serve as a vital food source for sea stars, shorebirds, and certain fish species.
Similar Species
Americardia biangulata (Strawberry Cockle), which has more pronounced ribs and a squared-off posterior end, and Trachycardium quadragenarium (Giant Pacific Cockle), which grows much larger and has prickly scales.
Beach Finding Tips
On Coronado Beach, look in the 'shell hash' lines left behind at low tide, specifically near the Hotel del Coronado or the Silver Strand. They are best found after a strong swell which churns up the sandy bottom where they live.
Notes
Coronado beach