Variable Coquina / Butterfly Shell / Wedge Shell
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Donacidae, Genus: Donax, Species: Donax variabilis · Donacidae (Wedge Clam family) · Bivalve (clams/two-shelled). The specimen appears to be a single valve (one half), categorized as a wedge-shaped or triangular shell.
Species
Donax variabilis (Confidence: High, despite image blur)
Shell Type
Bivalve (clams/two-shelled). The specimen appears to be a single valve (one half), categorized as a wedge-shaped or triangular shell.
Family
Donacidae (Wedge Clam family)
Size
Approximately 12-18mm in length. This is a standard size for a mature adult Coquina; they rarely exceed 25mm (1 inch).
Color & Pattern
Base color is a warm apricot or orange-brown with faint radiating bands. Interior often matches the exterior saturation. Coquinas are famous for polychromism, appearing in yellow, purple, white, and pink.
Rarity
Very Common. These are among the most abundant shells found on Atlantic and Gulf Coast beaches, often appearing by the thousands in a single tide line.
Habitat
Found in the intertidal zone of sandy beaches. They reside in the 'wash' zone where waves break, rapidly burrowing into saturated sand as waves recede.
Geographic Range
Western Atlantic, specifically from Virginia down to Florida and throughout the Gulf of Mexico to Texas and Mexico.
Description
A small, sturdy, wedge-shaped bivalve. One end is rounded while the other is more pointed or steeply angled. The surface is relatively smooth with very fine radial striae. The interior margin often features tiny serrations known as crenulations.
Key Features
Triangular/wedge profile; asymmetric shape with the posterior end much shorter than the anterior; distinctive color patterns that often resemble butterfly wings when both valves are attached.
Collector Value
Minimal financial value (pennies), but high aesthetic value for crafts. Highly sought after by children and casual beachcombers for their 'rainbow' variety.
Condition Notes
The specimen appears to be a weathered single valve. It shows significant blurring in the image, but the typical glossy finish appears dampened by abrasion. Overall grade: Fair (common beach-worn find).
Interesting Facts
The living animal is an 'active' burrower that uses its foot to jump and dive back into the sand to follow the tide. Humans once used them extensively to make 'Coquina broth,' a traditional coastal soup.
Ecological Role
Vital filter feeders that clean the water column and serve as a primary food source for shorebirds, crabs, and fish like the Pompano.
Similar Species
Donax fossor (which is smaller and usually less colorful) and Donax parvulus. It is distinguished from common clams by its specific wedge-like asymmetry.
Beach Finding Tips
Look in the 'swash zone' just as the tide is going out. You can often see them momentarily on the surface before they burrow. Use a fine-mesh sand sifter to find the most colorful paired sets.