Pacific Calico Scallop (also known as the Circular Calico Scallop)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: A. circularis · Pectinidae (Scallop family) · Bivalve (two-shelled), whole shell, fan shape
Species
Argopecten circularis
Shell Type
Bivalve (two-shelled), whole shell, fan shape
Family
Pectinidae (Scallop family)
Size
Approximately 1.5 to 2 inches in diameter, which is average for an adult specimen of this species. Adults typically range from 1 to 2.5 inches.
Color & Pattern
Displays a mottled and patterned combination of deep burgundy, purplish-brown, cream, and white in a calico arrangement. The colors are natural and vibrant with radial streaks and checkered color blocks along the prominent ribs. The interior exhibits a glossy finish with purplish hues near the hinge.
Rarity
Common, frequently found by beachcombers and divers within its natural geographic range.
Habitat
Inhabits shallow subtidal zones, commonly found in sandy or muddy substrates, often associated with eelgrass and seagrass beds in marine environments.
Geographic Range
Eastern Pacific Ocean, ranging from southern California down through the Gulf of California and along the coast of Mexico to Peru.
Description
An attractive and robust bivalve shell featuring a classic rounded fan shape with nearly symmetrical ears at the hinge. The exterior is heavily sculpted with roughly 18 to 22 well-defined radial ribs that feature fine scaly texture. The margins are scalloped to tightly interlock when closed, presenting a striking patchwork of earthy red and white hues.
Key Features
Distinguished by its nearly circular fan shape, roughly 20 prominent radial ribs, unequal or slightly asymmetrical auricles (ears) at the hinge plate, and characteristic calico mottling of brown, red, and white.
Collector Value
Low to moderate commercial value, but highly popular among casual beachcombers and beginner shell collectors due to their pleasing symmetry and vibrant colors. Typically sold in souvenir shops for a nominal price.
Condition Notes
Good condition. The specimen is an intact single valve with vibrant natural coloration retained and minimal edge wear. Graded as 'Good' to 'Fine' for a beach-collected single valve.
Interesting Facts
Scallops are among the few bivalves that can actively swim. By rapidly clapping their valves together, they expel water to jet-propel themselves away from predators like starfish. They also possess dozens of tiny, bright blue eyes along the mantle edge that can detect light and movement.
Ecological Role
Serves as an important filter feeder in coastal marine ecosystems, helping to clear water and cycle nutrients. They form a vital food source for numerous marine predators including rays, crabs, sea stars, and carnivorous gastropods.
Similar Species
Atlantic Calico Scallop (Argopecten gibbus), which is found in the Western Atlantic and Gulf of Mexico and has a more inflated shell profile. Distinguished primarily by geographic origin.
Beach Finding Tips
Look along sandy beaches and near sheltered bays or estuaries in the Gulf of California or Pacific Mexican coast, especially at low tide or after storm events that churn up shallow seagrass beds.