Atlantic Surf Clam (also known as Bar Clam, Skimmer Clam)
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Mactridae, Genus: Spisula, Species: Spisula solidissima · Mactridae (Trough shell family) · Bivalve (two-shelled, fan-shaped whole shell)
Species
Spisula solidissima
Shell Type
Bivalve (two-shelled, fan-shaped whole shell)
Family
Mactridae (Trough shell family)
Size
Approximately 3 to 4 inches in width, which is moderate for this species. Adult Atlantic Surf Clams typically range from 4 to 7 inches, with some exceptional specimens reaching up to 8 inches.
Color & Pattern
The exterior features a uniform creamy off-white to yellowish-tan base color with a smooth, chalky texture. The periostracum is mostly worn away, revealing the underlying calcium carbonate layer. The interior is a smooth, glossy porcelain white, sometimes displaying faint purple tinges near the hinge and muscle scars.
Rarity
Very Common
Habitat
Inhabits high-energy sandy ocean beaches and shallow subtidal zones from the low intertidal area down to depths of about 130 feet. They burrow completely into clean, shifting marine sands.
Geographic Range
Western Atlantic Ocean, primarily along the eastern coast of North America from the Gulf of St. Lawrence in Canada down to Cape Hatteras in North Carolina.
Description
A sturdy, triangular to oval-shaped bivalve shell with prominent concentric growth lines. The umbo is fairly prominent and located slightly off-center. The shell exhibits a smooth exterior surface, solid construction designed to withstand heavy surf action, and a clean white interior with strong internal hinge structures.
Key Features
Triangular-ovate outline, heavy and solid construction, prominent central umbones, lack of strong radial ribs (smooth concentric growth lines only), and a well-developed internal resilium (internal cartilage pit in the hinge).
Collector Value
Low collector value due to extreme abundance, though exceptionally large, pristine paired specimens are kept by casual beachcombers. Typically valued at under a dollar as a decorative item.
Condition Notes
Good condition whole single valve. Shows minor natural wear along the ventral margin and typical beach-tumbled smoothing, but retains structural integrity with no major cracks or predator boring holes.
Interesting Facts
The Atlantic Surf Clam is one of the largest bivalves in its range and supports a major commercial fishery for clam meat. They can use their muscular foot to dig rapidly back into the sand if dislodged by rough waves.
Ecological Role
Serves as an important prey species for bottom-feeding fish, sea stars, gulls, and predatory crabs. Acts as a benthic filter feeder, helping to clear organic particles from the water column.
Similar Species
Stout Tagelus (Tagelus plebeius) and Ocean Quahog (Arctica islandica). Distinguished by the distinct triangular shape and heavy, solid build compared to elongated razor clams or rounder quahogs.
Beach Finding Tips
Look along high-energy sandy Atlantic beaches after strong storms or nor'easters. Entire valves or fragments are frequently washed ashore near the high tide wrack line.