Atlantic Coquina, Bean Clam, Pompano Shell, Wedge Shell
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Donacidae, Genus: Donax, Species: variabilis · Donacidae (Wedge Shell or Coquina family) · Bivalve (two-shelled); this specimen is a single valve. Shape is wedge-shaped/triangular.
Species
Donax variabilis
Shell Type
Bivalve (two-shelled); this specimen is a single valve. Shape is wedge-shaped/triangular.
Family
Donacidae (Wedge Shell or Coquina family)
Size
Approximately 15-20mm (0.6-0.8 inches). Adults range from 10mm to 25mm.
Color & Pattern
Highly variable; this specimen shows concentric blue-gray and tan banding with a subtle radial pattern. The interior is typically polished purple or white.
Rarity
Very Common (found in massive colonies on sandy beaches).
Habitat
Sandy high-energy intertidal zones, specifically the wash zone of beaches where waves break.
Geographic Range
Western Atlantic: Virginia south to Florida and the Gulf of Mexico (Texas to the Caribbean).
Description
A small, sturdy, wedge-shaped bivalve with a smooth, glossy surface. The posterior end is short and rounded, while the anterior end is longer and more pointed. It features fine concentric growth lines and faint radial striae.
Key Features
Distinctive wedge/triangular shape; highly polished surface; small size; inner margin of the valves is finely serrated (crenulated).
Collector Value
Low monetary value due to extreme abundance, but high aesthetic value in collections due to the 'rainbow' of color variations possible in a single population.
Condition Notes
Good condition. Minimal erosion at the umbo (beaked hinge area). Some minor edge chipping but color remains vibrant. Rating: Fine.
Interesting Facts
Coquinas are famous for 'dancing' or rapidly re-burying themselves in the sand between wave cycles. In the 18th and 19th centuries, fossilized coquina deposits were used as a building stone (Coquina stone) in Florida because it was oddly resistant to cannon fire.
Ecological Role
Critical bridge in the food chain; they filter-feed on microscopic algae and are a primary food source for shorebirds (like sanderlings) and fish (like pompano).
Similar Species
Donax fossor (which is smaller and more northern) and Donax roemeri. Can be distinguished from small surf clams by its sharp wedge shape.
Beach Finding Tips
Look in the 'wash' area as the tide recedes. Watch for small holes or little shells popping out of the sand and re-burying themselves as waves pass.