Atlantic Calico Scallop (also known as Calico Scallop)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: Argopecten gibbus · Pectinidae (Scallop family) · Bivalve (two-shelled), whole shell valve fragment/worn individual, fan-shaped disc
Species
Argopecten gibbus
Shell Type
Bivalve (two-shelled), whole shell valve fragment/worn individual, fan-shaped disc
Family
Pectinidae (Scallop family)
Size
Approximately 0.5 inches in width and height, which is small and likely a juvenile or small adult valve. Typical adult species range is 1 to 2.5 inches.
Color & Pattern
Faint brownish-orange radial streaks and mottled patterns against an off-white background, characteristic of the 'calico' pattern. The colors are somewhat sun-bleached and weathered due to beach exposure. Interior shows pale white coloration with a purple-toned umbo area.
Rarity
Very Common, frequently washed up on beaches throughout its native range, especially along the southeastern United States and Florida coastlines.
Habitat
Shallow marine waters, typically found in sandy areas, shell gravel, or seagrass beds from the low intertidal zone down to depths of about 150 feet.
Geographic Range
Western Atlantic Ocean, ranging from North Carolina through the Gulf of Mexico, Florida, and the Caribbean down to South America.
Description
A small, delicate fan-shaped bivalve shell featuring prominent, rounded radial ribs (plicae) extending from the beak to the ventral margin. The margins are scalloped and uneven due to wear. A distinct hole, likely made by a predatory carnivorous snail or crab, is visible near the center of the valve.
Key Features
Equivalve to slightly inequivalve fan shape, rounded radial ribs (usually around 18 to 22), well-developed auricles (ears) at the hinge line, and characteristic mottled calico color patterns.
Collector Value
Very low value due to small size, wear, and structural damage (predation hole). They are extremely common and typically collected by casual beachcombers rather than advanced shell collectors.
Condition Notes
Fair to Poor condition. The shell is worn, sun-bleached, and features a noticeable predatory puncture hole near the center. It has low collectibility value for display, serving better as a casual beach find.
Interesting Facts
Unlike many bivalves that burrow or cement themselves, calico scallops are free-living and can swim actively by rapidly clapping their valves together to expel water, allowing them to escape predators like starfish.
Ecological Role
Calico scallops serve as an important food source for numerous marine predators including fish, rays, sea turtles, and octopuses. They are also filter feeders that help maintain water clarity in coastal ecosystems.
Similar Species
Atlantic Bay Scallop (Argopecten irradians) - which tends to have slightly flatter shells, fewer ribs (usually 17), and prefers shallower seagrass habitats.
Beach Finding Tips
Look along high-tide wrack lines on sandy ocean-facing beaches in Florida and the Gulf Coast, particularly after a storm or strong offshore winds.