Egg Cockle (also known as Isocardia Heart Cockle)
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Cardiidae, Genus: Americardia, Species: Americardia media · Cardiidae (Cockle family) · Bivalve (two-shelled), whole shell valves, fan-shaped to heart-shaped
Species
Americardia media
Shell Type
Bivalve (two-shelled), whole shell valves, fan-shaped to heart-shaped
Family
Cardiidae (Cockle family)
Size
Approximately 1.5 to 2 inches in length, which is average for this species. Adults typically range from 1 to 2.5 inches.
Color & Pattern
Pale yellowish-white to creamy tan base color with subtle brownish or reddish-brown flecks or banding towards the posterior margin. The colors appear natural and slightly sun-bleached. The interior is a smooth, glossy creamy white with faint yellow hues near the hinge.
Rarity
Common, frequently found by dedicated beachcombers and snorkelers in its natural geographic range.
Habitat
Found in shallow subtidal waters, typically in sandy substrates, sand flats, and offshore grass beds from the low intertidal zone down to moderate depths of several fathoms.
Geographic Range
Western Atlantic Ocean, ranging from North Carolina through Florida, the Gulf of Mexico, the Caribbean Sea, and down to Brazil.
Description
An attractive and sturdy bivalve shell characterized by its distinct, robust radial ribs that create a deeply serrated, scalloped margin. The shell has a swollen, rounded profile with prominent, inflated umboes that curve slightly inward. The exterior features strong, rounded ribs crossed by fine concentric growth lines, while the interior displays deeply grooved margins matching the exterior ribs.
Key Features
Distinctive inflated heart-like profile when viewed together, strong and rounded radial ribs numbering around 30 to 35, and deeply interlocking serrations along the ventral margin.
Collector Value
Low to moderate value. While widely collected and common in shell shops, fine matched pairs in gem condition are desirable for regional and family-level collections.
Condition Notes
Good to Fine condition. The valves are intact with minimal wear on the ribs, slight natural fading from exposure, and smooth margins with no major chips or fractures.
Interesting Facts
Cockles are capable of a remarkable leaping locomotion using their large, muscular foot to escape predators like starfish and carnivorous snails.
Ecological Role
Serves as an important filter feeder in coastal marine ecosystems, helping to clear suspended organic particles from the water column while acting as a prey source for fish, rays, and crabs.
Similar Species
Magnum Cockle (Dinocardium robustum), which is significantly larger and more elongate; and the Strawberry Cockle (Trachycardium egmontianum), which features sharper, more spiny ribs.
Beach Finding Tips
Look along high-tide wrack lines on exposed sandy beaches after storms, or snorkel in shallow sandy grass flats during calm low tides.