Coquina Clam (also known as Butterfly Clam, Wedge Shell, or Donax Clam)
Phylum: Mollusca, Class: Bivalvia, Order: Venerida, Family: Donacidae, Genus: Donax, Species: Donax variabilis · Donacidae (Wedge Clam / Coquina family) · Bivalve (single valve shown, exterior view). Shape: Asymmetrical, distinctly wedge-shaped or triangular.
Species
Donax variabilis (Confidence Level: Moderate to High based on shape, size, and color patterns)
Shell Type
Bivalve (single valve shown, exterior view). Shape: Asymmetrical, distinctly wedge-shaped or triangular.
Family
Donacidae (Wedge Clam / Coquina family)
Size
Estimated length is approximately 1.5 to 2.5 cm (0.6 to 1.0 inch). Typical adult specimens range from 1 to 2.5 cm.
Color & Pattern
Base color of off-white to cream with subtle yellowish-orange hues along the posterior slope and faint gray-violet concentric band rings. The colors appear slightly worn and surf-smoothed. Interior details are not visible in this view.
Rarity
Very Common. One of the most abundant washed-up shells found on sandy Atlantic beaches.
Habitat
Intertidal sandy surf zones. These marine clams live buried just beneath the sand surface where high-energy waves crash along sandy ocean beaches.
Geographic Range
Western Atlantic Ocean, ranging from Virginia down along the U.S. East Coast, around Florida, throughout the Gulf of Mexico, and into the Caribbean.
Description
A small, smooth, wedge-shaped single bivalve valve showing fine, concentric growth lines. The shell features a rounded anterior end tapering to a steeper, angled posterior end, giving it its iconic wedge outline. Surface texture is beach-worn but retains smooth, subtle concentric sculpture.
Key Features
Distinct triangular/wedge-shaped profile, small overall size, smooth surface with faint concentric growth rings, and characteristic anterior-to-posterior asymmetry.
Collector Value
Low monetary value due to extreme abundance ($0 - $1 USD), but highly valued by novice beachcombing enthusiasts and craft makers due to their diverse color variations and delicate wedge shapes.
Condition Notes
Beach-worn condition with smoothed edges and slightly faded coloration. Appears intact without major chips or boreholes. Collectibility Grade: Good / Fair (typical beachcombed single valve).
Interesting Facts
Coquina clams are famous for their ability to rapidly burrow into shifting sand using a strong foot as wave surges pass over them. They often occur in massive aggregations numbering thousands per square meter and are harvested to make traditional coquina clam broth.
Ecological Role
Serves as an essential filter feeder in surf zone ecosystems, consuming microalgae and organic debris. They are a crucial prey species for shorebirds, crabs (such as ghost crabs), and surf fish.
Similar Species
Donax fossor (Northern Coquina, which is generally smaller and less colourful) and Donax denticulatus (Caribbean Wedge Shell, which possesses stronger radial striae along the posterior edge).
Beach Finding Tips
Look near the tide line as waves recede. Watch for tiny bubbles or sudden burrowing movements in the wet sand right after a wave washes over the shore.