Coquina Clam (also known as Butterfly Shell, Bean Clam)
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Donacidae, Genus: Donax, Species: Donax variabilis · Donacidae (Bean Clam family) · Bivalve (two-shelled clam), whole shell, wedge-shaped
Species
Donax variabilis
Shell Type
Bivalve (two-shelled clam), whole shell, wedge-shaped
Family
Donacidae (Bean Clam family)
Size
Approximately 0.75 inches (1.9 cm) in length, which is average for an adult of this species. Adults typically range from 0.5 to 1 inch.
Color & Pattern
Extremely variable, displaying a rich gradient from a deep purplish-blue umbo to a warm golden-tan and orange body, accentuated by fine concentric growth lines. The colors are entirely natural and vivid.
Rarity
Very Common
Habitat
Intertidal zone of high-energy sandy ocean beaches, living just beneath the surface in the swash zone where waves break and wash ashore.
Geographic Range
Western Atlantic Ocean, from Virginia southwards along the coast of Florida and throughout the Gulf of Mexico.
Description
A small, charming wedge-shaped bivalve with a smooth yet finely sculpted exterior showing prominent concentric growth rings. The umbo (beak) is tinged with a dark bluish-purple hue that transitions smoothly into vibrant golden-orange and tan tones toward the rounded ventral margin.
Key Features
Wedge-shaped profile with a truncated posterior end, equilateral to inequilateral valve proportions, and an exceptionally rich array of color variations centered around a darker umbo.
Collector Value
Low individual monetary value due to abundance, but highly prized by beachcombers for creating decorative shell crafts and educational children's collections due to their stunning rainbow of colors.
Condition Notes
Gem condition. The shell is fully intact, completely unblemished, retains its original vibrant natural coloration with no bleaching, and shows no signs of predator boring holes or wear.
Interesting Facts
Coquina clams are famous for their ability to rapidly burrow back into the sand using their muscular foot when waves recede, and they use incoming waves to migrate up and down the beach to stay within the swash zone.
Ecological Role
Serves as a crucial food source for numerous shorebirds, fish, and crabs, and acts as an important biological filter feeder in high-energy beach ecosystems.
Similar Species
Donax fossor (Eastern Pacific Coquina) and Donax denticulatus (Carribbean Coquina), which can be distinguished primarily by geographic location and subtle variations in marginal denticulation.
Beach Finding Tips
Look in the wet intertidal zone just as receding waves pull back into the surf. Watch for tiny bubbles or tiny V-shaped jets of water escaping from the sand as the clams burrow.
Notes
Ocean isle beach