Pacific Giant Cockle or similar large bivalve (Likely a species of Pacific Calico Scallop or Atlantic Bay Scallop)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: Argopecten irradians · Pectinidae (Scallop family) · Bivalve (two-shelled), whole shell, fan shape
Species
Argopecten irradians (Atlantic Bay Scallop)
Shell Type
Bivalve (two-shelled), whole shell, fan shape
Family
Pectinidae (Scallop family)
Size
Approximately 2.5 to 3 inches in width, which is average for this species. Adults typically range from 2 to 3.5 inches.
Color & Pattern
Off-white or cream base color with distinct reddish-orange rectangular banding near the ventral margin, showing signs of natural sun-bleaching. The umbo features a deep purple coloration.
Rarity
Common
Habitat
Found in shallow marine waters, typically in seagrass beds and sandy or muddy substrates from the intertidal zone down to about 15 feet.
Geographic Range
Western Atlantic Ocean, extending from Nova Scotia down through the Gulf of Mexico and the Caribbean.
Description
A classic fan-shaped bivalve with prominent, rounded radial ribs radiating from the umbo. The hinge features distinct unequal auricles (ears), typical of the scallop family, and the margin is scalloped to match the exterior ribs.
Key Features
Nearly equilateral fan shape, prominent radial ribs (usually around 17-20), unequal auricles at the hinge line, and characteristic colored banding near the outer margin.
Collector Value
Low to moderate commercial value; commonly found in shell shops and popular among casual beachcombers rather than advanced specialists.
Condition Notes
Good condition with minor weathering and sun-bleaching. The structure is intact with slight hairline fractures visible near the center, grade is Good to Fine.
Interesting Facts
Scallops are among the few bivalves that can actively swim by clapping their valves together to expel water, and they possess dozens of tiny, bright blue eyes along the edge of their mantle.
Ecological Role
Serves as an important filter feeder, improving water quality, and acts as a vital food source for numerous marine predators including rays, crabs, and sea stars.
Similar Species
Atlantic Calico Scallop (Argopecten gibbus), which is more convex and typically features more erratic mottled color patterns rather than clean bands.
Beach Finding Tips
Look along sandy beaches near seagrass meadows after storms or high tides, particularly during the early morning hours.