Bean Clam (Variable Wedge Shell, Donax Clam)
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Donacidae, Genus: Donax, Species: Donax gouldii · Donacidae (Wedge Clams or Bean Clams) · Bivalve (Single Valve). Triangular or wedge-shaped.
Species
Donax gouldii
Shell Type
Bivalve (Single Valve). Triangular or wedge-shaped.
Family
Donacidae (Wedge Clams or Bean Clams)
Size
Approximately 0.75 inches (19mm). This is a mature size for this species; they typically range from 0.5 to 1 inch in length.
Color & Pattern
Pale cream to yellowish-tan base. It features faint, darker concentric growth lines and a subtle brownish-purple band near the posterior edge. The surface appears naturally polished with a slight sheen.
Rarity
Very Common. These are some of the most prolific shells found on Southern California sandy beaches like Coronado.
Habitat
Intertidal zone of sandy beaches. Found buried just beneath the surface in the 'wash' or 'swash' zone where waves break.
Geographic Range
Eastern Pacific coastline, specifically from Santa Cruz, California, down to Southern Baja California, Mexico.
Description
A small, wedge-shaped bivalve with a smooth, glossy exterior. The shell is sturdy for its size, featuring a distinctively truncated posterior end. The margins are finely serrated, and the hinge is comprised of strong cardinal teeth.
Key Features
Wedge-like triangular shape; asymmetric valves where one side is much longer than the other; smooth but finely radially striated surface; crenulated (toothed) inner margins.
Collector Value
Minimal monetary value ($0.10 - $0.50) due to extreme abundance. Desirable for hobbyists for 'memory jars' or craft work due to their pleasing symmetry and various color morphs.
Condition Notes
Fair to Good. The shell shows some signs of beach wear and slight edge chipping. The gloss is somewhat dulled by sand abrasion, and it is a single valve rather than a paired set. Grade: Good (Field Collected).
Interesting Facts
Known as 'surf clams,' these animals can migrate up and down the beach with the tide by popping out of the sand and letting waves carry them. They were historically used by indigenous people to make highly nutritious broth.
Ecological Role
Vital suspension feeders that filter phytoplankton from the water. They are a primary food source for shorebirds like Sanderlings and various species of surf fish and crabs.
Similar Species
Donax californicus (California Wedgeclam) which is more elongated and less robust; Donax variabilis (Coquina) found on the Atlantic coast.
Beach Finding Tips
Look in the 'wrack line' or at the very edge of the water during a receding tide. They often appear in large 'beds' or patches; if you find one, there are likely thousands nearby.
Notes
Coronado beach