Common Jackknife Clam (also known as Razor Clam)
Phylum: Mollusca, Class: Bivalvia, Order: Adapedonta, Family: Pharidae, Genus: Ensis, Species: Ensis directus · Pharidae (Jackknife and razor clam family) · Bivalve (two-shelled), whole shell, elongated curved tubular shape
Species
Ensis directus
Shell Type
Bivalve (two-shelled), whole shell, elongated curved tubular shape
Family
Pharidae (Jackknife and razor clam family)
Size
Approximately 1 inch long, which is a juvenile specimen. Adults typically range from 4 to 7 inches in length.
Color & Pattern
Olive green to brownish periostracum covering a whitish calcareous base layer, with subtle fine concentric growth lines. The interior is glossy white, sometimes with purple tinges.
Rarity
Very Common
Habitat
Inhabits intertidal and shallow subtidal zones, burrowing vertically deep into clean or muddy sand along high-energy marine coastlines and estuarine sandbars.
Geographic Range
Native to the Western Atlantic coast of North America from Canada down to Florida, and introduced to European waters.
Description
A remarkably sleek and slender bivalve resembling an old-fashioned folding pocketknife. The shell is strongly elongated, slightly curved, with parallel dorsal and ventral margins and smooth, rounded ends. Its glossy greenish-brown exterior highlights delicate growth rings.
Key Features
Extremely elongated straight or slightly curved tubular shape, truncate ends, and a prominent periostracum ranging from olive to dark brown.
Collector Value
Low commercial or collector value due to abundance, though whole, undamaged adult specimens are often kept by casual beachcombers.
Condition Notes
Good condition for a beach-found juvenile specimen; intact margins with minor wear, retaining much of its original greenish-brown periostracum layer.
Interesting Facts
Jackknife clams are exceptionally fast burrowers, capable of digging rapidly into wet sand using a muscular foot to escape predators within seconds.
Ecological Role
Serves as an important prey species for shorebirds, fish, and crabs, and functions as a filter feeder helping to maintain water quality in coastal ecosystems.
Similar Species
Tagelus plebeius (Stout Tagelus), which is broader, squarer, and less curved compared to the slender Ensis directus.
Beach Finding Tips
Look near the water line during extremely low tides in the wet sand where small keyhole-shaped or 'figure-eight' siphon holes indicate active burrows.
Notes
Outer banks, North Carolina on Kill Devils Hill beach