Coquina Clam (Butterfly Shell)
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Donacidae, Genus: Donax, Species: Donax variabilis · Donacidae (Bean Clam family) · Bivalve, whole shell, wedge or fan-shaped
Species
Donax variabilis
Shell Type
Bivalve, whole shell, wedge or fan-shaped
Family
Donacidae (Bean Clam family)
Size
Approximately 0.5 inches (12-15 mm), which is average for an adult specimen of this species. Typical range is 0.3 to 0.8 inches.
Color & Pattern
Solid chalky white due to sun-bleaching or wear, lacking the typical vibrant purples, pinks, yellows, or radial banding found in fresh live specimens.
Rarity
Very Common
Habitat
High-energy intertidal zone of sandy ocean beaches, particularly in the swash zone where waves break and wash up onto the shore.
Geographic Range
Western Atlantic Ocean, from Virginia south along the Florida coast and throughout the Gulf of Mexico.
Description
A tiny, sturdy, wedge-shaped bivalve shell with fine concentric growth lines and a smooth, eroded exterior showing a solid white coloration from wave action and sun exposure.
Key Features
Wedge shape with a truncated posterior end, equilateral valves, and smooth inner margins characteristic of the genus Donax.
Collector Value
Low monetary value, frequently collected in large quantities by beachcombers for crafts rather than by advanced conchologists due to their abundance.
Condition Notes
Fair condition; heavily worn and completely sun-bleached to a uniform white with minor edge chipping, typical of beach-worn drift specimens.
Interesting Facts
Coquina clams are famous for their ability to burrow back into the sand in mere seconds using their muscular foot before the next wave washes them away.
Ecological Role
Serves as an important food source for numerous shorebirds, fish, and crabs, while helping to filter organic particles from the surf zone.
Similar Species
Donax fossor (Eastern Atlantic Coquina), which tends to be slightly more elongate and found in more northerly regions.
Beach Finding Tips
Look in the wet swash zone of sandy ocean-facing beaches during low tide, specifically watching for small bubbles or movement in the sand as they burrow.