Coquina, Variable Coquina, Donax Clam
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Donacidae, Genus: Donax, Species: D. variabilis · Donacidae (Wedge clam family) · Bivalve (single valve shown); wedge-shaped or triangular.
Species
Donax variabilis
Shell Type
Bivalve (single valve shown); wedge-shaped or triangular.
Family
Donacidae (Wedge clam family)
Size
Approximately 12-15mm in length. This is a mature specimen; the species typically ranges from 10mm to 25mm.
Color & Pattern
Vibrant golden-yellow to orange base color with faint concentric banding and radiating white rays. The umbo (beak) is white. The color appears natural and well-preserved rather than sun-bleached.
Rarity
Very Common; these are among the most numerous shells found on Atlantic sandy beaches.
Habitat
High-energy intertidal zones on sandy beaches, living just beneath the surface of the sand in the wash zone.
Geographic Range
Western Atlantic, from Virginia south to Florida and the Gulf of Mexico to Texas.
Description
A small, sturdy wedge-shaped bivalve with a smooth, glossy exterior. The shell features fine concentric growth lines and very subtle radial striae. This specimen displays a highly desirable golden-sunburst color phase.
Key Features
Distinctive wedge-like triangular shape, posterior end rounded and anterior end elongated; inner margin of the shell is finely serrated (crenulated).
Collector Value
Minimal monetary value (essentially $0-$1) due to abundance, but highly valued by hobbyists for 'color matching' and crafts because of their rainbow-like variety.
Condition Notes
Good to Fine condition. The valve is intact with no significant chipping on the margins. The natural luster is still present, suggesting it was recently washed up.
Interesting Facts
Coquinas are famous for 'surfing' the tides; they use their foot to quickly re-bury themselves every time a wave moves the sand. They were historically used by early Florida settlers to make a thin broth known as 'Coquina Broth'.
Ecological Role
Vital 'filter feeders' that clean the water column and serve as a primary food source for shorebirds, crabs, and certain fish like Pompano.
Similar Species
Donax fossor (which is smaller and usually less colorful) and Donax roemeri (found further west in the Gulf).
Beach Finding Tips
Look in the 'wash' area where waves are currently breaking. Watch for tiny bubbles or 'V' shapes in the wet sand as waves recede, which indicates they are burrowing.