Measled Bean Clam, also known as Butterfly Bean, Coquina Clam (variant)
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Donacidae, Genus: Donax, Species: Donax denticulatus · Donacidae (Bean Clam and Coquina family) · Bivalve (two-shelled), whole shell, wedge or bean-shaped
Species
Donax denticulatus
Shell Type
Bivalve (two-shelled), whole shell, wedge or bean-shaped
Family
Donacidae (Bean Clam and Coquina family)
Size
Approximately 10 mm in length, which is average for this small species. Adults typically range from 8 mm to 25 mm.
Color & Pattern
The base color is a creamy off-white or light tan, adorned with distinctive, neatly arranged rows of tiny reddish-brown spots or dots radiating from the umbo toward the ventral margin. The surface has a glossy, polished appearance with natural coloration.
Rarity
Common to Very Common, frequently found by beachcombers in its natural range.
Habitat
Found in high-energy sandy intertidal zones, surf zones, and swash zones of exposed sandy beaches, where they actively burrow into the shifting sand.
Geographic Range
Widespread throughout the tropical Western Atlantic, including the Caribbean Sea, the Gulf of Mexico, Florida, and south to Brazil.
Description
A tiny, robust, wedge-shaped bivalve with a smooth, glossy exterior finish. The umbo is slightly off-center, and the shell displays charming dotted patterns radiating downward. The margins are finely denticulated, giving the species its specific name, and the overall form is compact and pebble-like.
Key Features
Wedge or bean-shaped profile, glossy texture, distinctive rows of tiny brown spots, and finely toothed inner margins along the valve edges.
Collector Value
Low commercial value due to abundance, but highly prized by amateur beachcombers for making shell crafts, jewelry, and miniature collections.
Condition Notes
Gem condition; the shell is completely intact with vibrant natural color, highly polished surface, no visible wear, chips, or predator boring holes.
Interesting Facts
Donax clams are famous for their rapid burrowing abilities, using their muscular foot to dig back into the sand within seconds when uncovered by receding waves. They actively migrate up and down the beach with the tides to stay within the swash zone.
Ecological Role
Serves as an important food source for shorebirds, fish, and crabs in the intertidal zone. They act as suspension feeders, filtering organic matter and phytoplankton from the water column.
Similar Species
Donax variabilis (Coquina clam), which tends to be more triangular, highly variable in solid colors and zigzag bands, and lacks the distinct dotted pattern of Donax denticulatus.
Beach Finding Tips
Look in the wet swash zone of tropical or Caribbean sandy beaches just as a wave recedes. Watch for tiny bubbles or slight movements in the sand where they rapidly burrow.