Atlantic Calico Scallop (also known as Calico Scallop)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: A. gibbus · Pectinidae (Scallop family) · Bivalve (two-shelled), whole shell, fan-shaped disc
Species
Argopecten gibbus
Shell Type
Bivalve (two-shelled), whole shell, fan-shaped disc
Family
Pectinidae (Scallop family)
Size
Approximately 1.5 inches in diameter, which is typical for an adult specimen of this species. Adults generally range from 1 to 2.5 inches.
Color & Pattern
This particular specimen exhibits an unusually dark, near-black coloration, likely due to mineral staining or fossilization processes (often found in dark creek beds or ancient deposits). Typically, calico scallops feature mottled patterns of reddish-brown, purple, orange, or maroon patches on a whitish background, resembling calico fabric.
Rarity
Common overall as a beach find in its native range, though specimens with this specific dark, fossilized, or melanistic coloration are less commonly found and prized by local collectors.
Habitat
Shallow subtidal marine environments, typically found in sandy or shelly substrates, often among seagrass beds in waters ranging from intertidal zones down to about 150 feet.
Geographic Range
Western Atlantic Ocean, ranging from North Carolina south through Florida, the Gulf of Mexico, the Caribbean, and down to the West Indies and parts of South America.
Description
A classic fan-shaped bivalve featuring distinct, rounded radiating ribs (approximately 18 to 22 ribs) that span from the beak (umbo) to the outer ventral margin. The ears (auricles) at the hinge line are somewhat uneven, characteristic of the genus Argopecten. The exterior has a finely textured, ridged surface.
Key Features
Equivalve or nearly equivalve fan shape, approximately 18-22 prominent radiating ribs, and distinct uneven auricles (ears) flanking the beak at the hinge line.
Collector Value
Moderately valued by casual collectors. While standard color morphs are very common and inexpensive, specimens with unique dark mineral stains or fossilization appeal to localized collectors and are often sold in novelty shops.
Condition Notes
The shell appears to be a solid, intact single valve in good condition. The dark coloration suggests it may be a fossil or sub-fossil specimen from a deposit rather than a freshly beach-collected shell. Collectibility grade is Good to Fine.
Interesting Facts
Unlike many bivalves, calico scallops are capable of swimming by rapidly clapping their valves together to expel water jets, allowing them brief bursts of escape movement from predators like starfish.
Ecological Role
Calico scallops serve as important filter feeders, improving water clarity, and form a vital food source for numerous marine predators including fish, rays, sea turtles, and carnivorous snails.
Similar Species
Atlantic Bay Scallop (Argopecten irradians), which tends to be slightly larger, more rounded, and has broader, fewer ribs (usually 17 or fewer) compared to the Calico Scallop.
Beach Finding Tips
Look along high-tide wrack lines on sandy ocean-facing beaches, particularly after storms or heavy onshore winds in Florida and the southeastern United States.