Common Atlantic Calico Clam (also known as the Pitted Donax or Wedge Shell)
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Donacidae, Genus: Donax, Species: Donax variabilis · Donacidae (Wedge shell family) · Bivalve (two-shelled), whole shell, wedge or triangular shape
Species
Donax variabilis
Shell Type
Bivalve (two-shelled), whole shell, wedge or triangular shape
Family
Donacidae (Wedge shell family)
Size
Approximately 0.5 inches (1.3 cm) in length, which is average for an adult specimen of this species. Adults typically range from 0.4 to 0.75 inches.
Color & Pattern
Displays a smooth, yellowish-cream base color with a subtle grayish-blue band radiating from the umbo toward the ventral margin. Fine, delicate radial striations texture the surface near the apex.
Rarity
Very Common
Habitat
Found in high-energy intertidal zones on sandy ocean beaches, particularly in the swash zone where waves constantly break and recede.
Geographic Range
Western Atlantic Ocean, ranging from Virginia down through Florida and the Gulf of Mexico to the Caribbean.
Description
A small, sturdy, wedge-shaped bivalve with a smooth, glossy exterior and a distinctively pointed umbo. The margin is finely crenulated, and the shell features a charmingly compact profile designed to withstand heavy surf.
Key Features
Wedge-shaped profile, asymmetric triangular outline, prominent umbo, and finely toothed inner margins along the ventral edge.
Collector Value
Low monetary value due to extreme abundance, but popular among beginning beachcombers and used extensively in shell craft.
Condition Notes
The specimen is an intact, whole single valve in good to fine condition, displaying natural coloration with minimal wear and no major structural fractures.
Interesting Facts
These tiny clams are famous for their rapid burrowing behavior. When a wave recedes, they rapidly dig themselves back into the sand using a muscular foot before the next wave arrives to wash them away.
Ecological Role
Serves as an important food source for shorebirds, fish, and crabs, while acting as a filter feeder that helps maintain water quality in the surf zone.
Similar Species
Coquina Clam (Donax dentifer) or other Donax species, which can be distinguished by subtle variations in color banding, size, and the intensity of marginal teeth.
Beach Finding Tips
Look along sandy ocean-facing beaches right at the water's edge in the wet sand where waves wash up, especially during low tide.