Common Egg Cockle (also known as the Egg Cockle)
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Cardiidae, Genus: Laevicardium, Species: Laevicardium mortoni · Cardiidae (Cockle family) · Bivalve (two-shelled clam), whole shell valve, ovate to subtrigonal shape
Species
Laevicardium mortoni
Shell Type
Bivalve (two-shelled clam), whole shell valve, ovate to subtrigonal shape
Family
Cardiidae (Cockle family)
Size
Approximately 0.5 inches (12-15 mm) in length, which is average for this diminutive species. Adults typically range from 0.4 to 0.8 inches.
Color & Pattern
Uniformly off-white, cream, or pale yellowish with faint, delicate growth lines. The surface has a smooth to polished appearance with very subtle radial striations.
Rarity
Common, though easily overlooked due to its small size and pale, unassuming coloration.
Habitat
Found in shallow marine and estuarine waters, typically buried just beneath the surface in fine sand, muddy sand, or seagrass beds in the intertidal to shallow subtidal zones.
Geographic Range
Western Atlantic Ocean, ranging from Nova Scotia, Canada, down the Atlantic coast of the United States, through the Gulf of Mexico, and into the Caribbean.
Description
A small, delicate, and smooth bivalve shell with an inflated, egg-like profile. The umbo is prominent and slightly curved. The exterior surface lacks the heavy ribs characteristic of many other cockles, presenting instead a smooth, glossy finish with fine, concentric growth lines.
Key Features
Smooth, polished exterior surface lacking prominent radial ribs, ovate-inflated shape, small size, and a prominent umbo distinguishing it from more heavily sculpted cockles.
Collector Value
Low to moderate commercial value, primarily collected as part of micro-mollusk collections or general regional beachcombing assemblages. Usually valued at less than a dollar per specimen.
Condition Notes
Single valve in good condition with minor natural wear along the ventral margin. Coloration is slightly sun-bleached. Overall collectibility grade is Good.
Interesting Facts
Despite belonging to the cockle family Cardiidae, which usually feature pronounced ribbed ornamentation, members of the genus Laevicardium are notably smooth and glossy, giving them an egg-like appearance.
Ecological Role
Serves as an important prey item for small carnivorous gastropods, shorebirds, and bottom-feeding fish. Contributes to benthic bioturbation as it burrows through surface sediments.
Similar Species
Prunum apicinum (Marginella) can occasionally be confused in silhouette by novice beachcombers, though it is a univalve gastropod. Other small bivalves like Gemma gemma are much smaller and more heavily rounded.
Beach Finding Tips
Look along protected sandy or muddy bays and barrier island beaches after high tides or storms. Sifting through shell hash and fine drift lines using a micro-shell screen yields the best results.