Coquina Clam (also known as Butterfly Shell, Pipi, or Donax)
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Donacidae, Genus: Donax, Species: Donax variabilis · Donacidae (Bean clam family) · Bivalve (two-shelled clam), whole shells and fragments, wedge or bean shape
Species
Donax variabilis
Shell Type
Bivalve (two-shelled clam), whole shells and fragments, wedge or bean shape
Family
Donacidae (Bean clam family)
Size
Approximately 0.5 to 1 inch (12-25 mm) in length, which is average for this species.
Color & Pattern
Extremely variable in color, ranging from pure white, yellow, orange, pink, purple, blue to brown, often featuring radiating rays, zigzag patterns, or concentric growth bands. The colors are entirely natural and typical of a beach drift made up of mixed color morphs. Interiors are often dark purple or porcelain white.
Rarity
Very Common. These shells accumulate densely on specific shell beaches, forming vast shell deposits often referred to as 'coquina shell hash'.
Habitat
High-energy sandy intertidal zones of ocean beaches, where they burrow rapidly into the sand in the swash zone.
Geographic Range
Western Atlantic Ocean, from Virginia southwards along the Florida coast and throughout the Gulf of Mexico.
Description
A dense aggregation of small, wedge-shaped bivalve shells featuring smooth to finely sculptured concentric lines and radial striations. The shells are asymmetrical, with a short posterior and elongated anterior end, displaying a remarkable polymorphous array of pastel and vibrant colors.
Key Features
Wedge shape, glossy texture, highly variable color polymorphism, fine radial sculpturing, and small compact size.
Collector Value
Low individual monetary value, but highly prized by beachcombers for bulk crafting, resin art, and educational study due to their brilliant natural color arrays.
Condition Notes
A mixture of whole valves, paired valves, and fragmented shell hash. Many specimens show natural beach wear and sun bleaching, but retain vibrant color variations. Collectibility grade ranges from Good to Fair for individual specimens, but exceptional as a representative biogenic beach deposit.
Interesting Facts
Coquina clams are famous for their ability to rapidly burrow back into the sand using their muscular foot when exposed by receding waves. They actively migrate up and down the beach with the tides to maintain their position in the swash zone.
Ecological Role
Serves as an essential food source for shorebirds, fish, and crabs, and acts as an active filter feeder helping to clean coastal waters.
Similar Species
Donax denticulatus (Caribbean coquina), which tends to have more prominent denticles along the shell margin.
Beach Finding Tips
Look along high-energy sandy beaches during low tide, particularly near the wrack line or in concentrated shell deposits where wave action sorts small bivalves.