California Donax (Alternate names: Bean Clam, Wedge Shell)
Phylum: Mollusca, Class: Bivalvia, Order: Cardiida, Family: Donacidae, Genus: Donax, Species: Donax gouldii · Donacidae (Wedge Clam or Bean Clam family) · Bivalve (Two-shelled); Single valve (half-shell) found; Wedge or triangular shape.
Species
Donax gouldii
Shell Type
Bivalve (Two-shelled); Single valve (half-shell) found; Wedge or triangular shape.
Family
Donacidae (Wedge Clam or Bean Clam family)
Size
Approximately 0.75 inches (19mm). This is a mature size for this species; they typically range from 0.5 to 1 inch.
Color & Pattern
Warm yellow and cream base with subtle concentric growth bands. Some rays of lighter tan are visible. The colors appear natural and well-preserved rather than bleached, showing the common 'creamy yellow' color morph.
Rarity
Very Common. These can often be found by the thousands on Southern California beaches after high surf or during population blooms.
Habitat
Intertidal zone of sandy ocean beaches. These clams live just beneath the surface of the sand in the 'swash zone' where waves break.
Geographic Range
Eastern Pacific coast, primarily from Santa Cruz, California, south to southern Baja California, Mexico. The location of Coronado Beach is exactly in the heart of its range.
Description
A small, sturdy, wedge-shaped bivalve with a smooth, polished exterior. The shell is heavier than it looks, designed to withstand the crushing force of heavy surf. It features a distinctively angled posterior and a rounded anterior, giving it a 'bean' or 'wedge' appearance. The surface has very fine, almost microscopic radial striations and clear growth lines.
Key Features
Triangular/Wedge-like shape; heavy, thickened shell for its small size; smooth glossy texture; and the specific geographic location (San Diego area).
Collector Value
Low monetary value ($0.50 - $1.00) due to abundance, but high sentimental value for beachcombers. They are prized by crafters for 'shell art' due to their uniform size and pretty colors.
Condition Notes
Good condition. The valve is intact with a sharp margin and visible color. It shows minor beach wear (slight smoothing of the hinge area), but no predator drill holes or major chips. Collectibility grade: Fine.
Interesting Facts
Donax gouldii is famous for 'population explosions' where millions appear on a single beach for a year or two, followed by years of near absence. They use a muscular foot to rapidly re-bury themselves every time a wave washes them out of the sand.
Ecological Role
Crucial filter feeders that process organic matter in the surf zone. They are a primary food source for shorebirds like Willets and Sanderlings, as well as surf fish and rays.
Similar Species
Donax californicus (California Wedgeclam) which is more elongated and prefers quiet bays rather than open surf beaches.
Beach Finding Tips
Look in the 'wash' area as the tide is going out. You will often see them as small bumps or 'v' shapes in the sand as they try to burrow back down after a wave passes. They are most plentiful at Coronado following winter storms.
Notes
Coronado beach