Coquina, Butterfly Shell, Wedge Shell
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Donacidae, Genus: Donax, Species: Donax variabilis · Donacidae (Wedge shell or Coquina family) · Bivalve (Two-shelled); Single valve (half-shell); Wedge-shaped.
Species
Donax variabilis (High confidence)
Shell Type
Bivalve (Two-shelled); Single valve (half-shell); Wedge-shaped.
Family
Donacidae (Wedge shell or Coquina family)
Size
Approximately 0.5 to 0.75 inches (12-19mm). This is typical for a mature specimen of this species, which rarely exceeds 1 inch.
Color & Pattern
Soft pastel cream to pale orange-yellow base. It shows subtle concentric growth lines. Naturally polished appearance; these shells are famous for their immense color variety including pink, yellow, blue, and striped patterns.
Rarity
Very Common. They can often be found by the thousands on Southern US beaches, though finding perfectly matched pairs is the collector's goal.
Habitat
Intertidal zone of sandy beaches. They live in the 'wash' area where waves break, constantly burrowing into the sand as the tide moves.
Geographic Range
Western Atlantic, specifically from Virginia south to Florida into the Gulf of Mexico and the Caribbean.
Description
A small, sturdy, wedge-shaped bivalve with a smooth, glossy exterior. The shell is inequilateral with the posterior end being very short and steeply angled, while the anterior end is longer and more rounded. The interior is usually smooth and often mirrors the exterior's vibrant coloration.
Key Features
Distinctive 'wedge' or triangular shape; smooth surface with fine concentric lines; small size; and an offset 'beak' or umbo near the posterior end.
Collector Value
Low monetary value but high aesthetic value. They are popular for 'jar displays' and crafts. Rare color morphs or perfectly hinged 'butterfly' pairs are the most desirable to hobbyists.
Condition Notes
Good condition. It appears to be a single beach-worn valve. The edges are slightly softened by wave action, and the color is slightly muted, suggesting it has been exposed to the sun or rolling in the surf for some time. Collectibility Grade: Good.
Interesting Facts
Coquinas are famous for their 'dancing' behavior—they use a muscular foot to quickly re-bury themselves every time a wave uncovers them. Historically, they were used to make 'Coquina broth' and the compacted shells of ancient deposits were used as building stone (Coquina stone) for Spanish forts in Florida.
Ecological Role
Vital 'filter feeders' that clean the water column; they serve as a primary food source for shorebirds like Sanderlings and various species of crabs and fish.
Similar Species
Donax fossor (which is smaller and found further north) and Donax roemeri. It is distinguished from other small clams by its unique asymmetrical wedge profile.
Beach Finding Tips
Look in the 'swash zone' as the tide goes out. You may see small holes or 'tufts' in the sand where they are burrowing. They are most easily found by sieving handfuls of wet sand near the water's edge.