Coquina Shell (also known as Donax Shell, Coquina Clam, Wedge Shell, or Butterfly Shell)
Phylum: Mollusca | Class: Bivalvia | Subclass: Heterodonta | Order: Cardiida | Family: Donacidae | Genus: Donax | Species: Donax variabilis · Donacidae (Wedge Clam / Coquina family) · Bivalve (two-shelled mollusk). The image displays a complete pair of matching double valves attached at the hinge line (often called a 'butterfly shell' layout). Shape is elongated, wedge-like, triangular, or fan-shaped.
Species
Donax variabilis (Confidence: High)
Shell Type
Bivalve (two-shelled mollusk). The image displays a complete pair of matching double valves attached at the hinge line (often called a 'butterfly shell' layout). Shape is elongated, wedge-like, triangular, or fan-shaped.
Family
Donacidae (Wedge Clam / Coquina family)
Size
Approximately 12 mm to 18 mm (about 0.5 to 0.7 inches) long. This size is typical to average for adult Donax variabilis, which generally range between 10 mm and 25 mm (0.4 to 1.0 inch).
Color & Pattern
Displays a striking dual-tone gradient with a rosy-pink to salmon-orange outer margin and a soft yellowish-cream to white center near the umbo. Subtle concentric growth lines and fine radial striae are visible across the smooth surface.
Rarity
Very Common. Coquina clams occur in vast colonies along sandy surf beaches and are frequently washed ashore.
Habitat
Intertidal zones on high-energy sandy ocean beaches. Found buried just beneath the surface in the wet sand swept by incoming and outgoing surf.
Geographic Range
Western Atlantic Coast, ranging from Virginia south to Florida, throughout the Gulf of Mexico, and down to the Caribbean.
Description
A pristine double-valve specimen of the Variable Coquina Clam resting open like a pair of butterfly wings. The shell exhibits a smooth exterior with an iridescent sheen, wedge-shaped symmetry, and vibrant gradient tones from bright coral pink to creamy ivory.
Key Features
Distinctive wedge-shaped elongate valves, smooth glossy surface with fine radial lines, prominent colorful bands, and paired valves connected at the fragile hinge, mimicking a butterfly.
Collector Value
Low monetary value ($1 - $5) due to extreme abundance, but highly cherished by beachcombers and crafters, especially intact double-valve specimens preserving original colors.
Condition Notes
Excellent / Fine to Gem condition. Both valves remain naturally joined at the hinge ligament (a 'paired double valve'), preserving bright vivid coloration and glossy luster without signs of severe erosion or sun-bleaching.
Interesting Facts
Coquinas are famous for their remarkable color polymorphism; virtually no two shells look identical. When washed out of the sand by a wave, live coquinas can rapidly rebury themselves using a muscular foot in just seconds before the wave retreats.
Ecological Role
Crucial primary consumers in surf-zone food webs that filter plankton and organic detritus from water. They serve as a primary food source for shorebirds, crabs, fish, and predatory snails.
Similar Species
Donax fossor (smaller, less colorful, found farther north), Donax denticulatus (Caribbean Wedge Shell), and tellin species such as Eurytellina lineata (Roseate Tellin).
Beach Finding Tips
Look along the wet shoreline right at the water's edge as waves recede. Watch for tiny bubbles or small mounds where live coquinas rebury themselves, or search the freshly deposited shell drift lines for open paired valves.