California Bean Clam (also known as the Gould's Donax)
Phylum: Mollusca; Class: Bivalvia; Order: Cardiida; Family: Donacidae; Genus: Donax; Species: Donax gouldii · Donacidae (Wedge clam or Bean clam family) · Bivalve (single valve/half shell); Shape is wedge-like or triangular-oval.
Species
Donax gouldii (Confidence level: 95%)
Shell Type
Bivalve (single valve/half shell); Shape is wedge-like or triangular-oval.
Family
Donacidae (Wedge clam or Bean clam family)
Size
Approximately 12-18mm in length. This is a mature size for this species; they rarely exceed 1 inch (25mm).
Color & Pattern
Glossy cream-white base with concentric yellowish-orange banding. The pattern shows distinct growth rings with a slight radial ray toward the posterior. The interior is typically white with a polished porcelain-like finish.
Rarity
Very Common. These shells can often be found by the thousands in 'colonies' along the shoreline after a high tide.
Habitat
Intertidal zone of sandy beaches with high wave action. They are 'surf clams' that live just beneath the sand surface in the wash zone.
Geographic Range
Eastern Pacific coast, specifically from Santa Cruz, California, south to southern Baja California, Mexico. Very common on San Diego beaches like Coronado.
Description
A small, sturdy, wedge-shaped bivalve with a highly polished, glossy exterior. The shell is heavier than it looks, designed to withstand the crushing force of the surf. One side is distinctly more rounded while the other tapers to a blunt point, giving it its characteristic 'bean' or 'wedge' appearance. The surface is smooth with fine concentric growth lines.
Key Features
Asymmetrical wedge shape; high-gloss 'wet' look even when dry; heavy thickness for such a small shell; presence of fine serrations on the inner ventral margin (felt with a fingernail).
Collector Value
Low monetary value ($0.50 - $1.00) due to extreme abundance, but high aesthetic value for 'sand jar' displays or beginner collections due to their varied colors (ranging from purple to yellow to white).
Condition Notes
The specimen appears to be a single 'dead-collected' valve. It retains excellent color and gloss, though the hinge ligament is gone. Collectibility grade: Fine.
Interesting Facts
These clams are 'surf jumpers'—they use a muscular foot to pop out of the sand when waves hit, allowing the current to move them up or down the beach to find the best feeding spot. Historically, they were so abundant that they were harvested to make a flavorful clam broth.
Ecological Role
A vital filter feeder that processes organic matter in the surf zone. They are a primary food source for shorebirds like Willets and Sanderlings, as well as surf fish.
Similar Species
Donax californicus (California Wedge Clam), which is thinner, more elongated, and typically found in calmer bays rather than the open surf of Coronado.
Beach Finding Tips
Look at the 'swash zone' as the tide is receding. You will often see small V-shaped ripples in the sand where live clams are buried; dead shells accumulate in the shell hash lines during spring tides.
Notes
Coronado beach