Coquina, Variable Wedge Shell, Bean Clam
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Donacidae, Genus: Donax, Species: Donax variabilis · Donacidae (Wedge shell family) · Bivalve (single valve shown); wedge-shaped and compressed
Species
Donax variabilis (High confidence)
Shell Type
Bivalve (single valve shown); wedge-shaped and compressed
Family
Donacidae (Wedge shell family)
Size
Approximately 0.5 to 0.75 inches (12-19 mm). This is a standard size for a mature adult of this species.
Color & Pattern
Base color of pale pinkish-white with concentric tan and orange-brown banding towards the margins. These shells are famously polymorphic, appearing in solid or striped patterns of yellow, purple, white, and orange.
Rarity
Very Common; these are among the most frequently encountered shells on southeastern US beaches.
Habitat
Intertidal surf zone of sandy beaches. They live just below the surface of the sand where the waves break.
Geographic Range
Western Atlantic, ranging from Virginia down to Florida and throughout the Gulf of Mexico to Texas.
Description
A small, sturdy, wedge-shaped bivalve with a smooth, glossy exterior finish. The shell is inequilateral, meaning the beak (umbo) is positioned toward the posterior end. It features fine concentric growth lines and very faint radial striae. The interior is often polished and may show a purple or yellow tint.
Key Features
Distinctive wedge or triangular shape with a rounded anterior and a sharply sloped posterior; small size; smooth texture; presence of colorful concentric bands on the outer margin.
Collector Value
Minimal monetary value (less than $1) due to extreme abundance. However, they are highly desirable for craft enthusiasts and beginner collectors due to their rainbow of color variations.
Condition Notes
Good / Collector Grade. The valve is intact without major chips, though there is slight dulling of the polish which is typical for beach-found specimens. The color bands remain vibrant.
Interesting Facts
Coquinas are highly mobile; they use a muscular foot to 'surf' with the incoming and outgoing tides to maintain their position in the ideal surf zone. In some cultures and historically in Florida, they were collected in large quantities to make a flavorful broth called 'Coquina broth'.
Ecological Role
Primary consumer and filter feeder. They play a vital role as a food source for shorebirds (like Sanderlings), crabs, and surf-dwelling fish. They are indicators of a healthy, high-energy beach ecosystem.
Similar Species
Donax fossor (stouter and found further north) and Donax roemeri. It is distinguished from other small clams by its unique wedge-like, asymmetrical shape.
Beach Finding Tips
Look at the water's edge right as a wave recedes. You will often see them quickly burrowing back into the wet sand. They are most easily found in the 'wash' line of shells at low tide.