Calico Scallop (Alternating Scallop)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: Argopecten gibbus · Pectinidae (Scallop family) · Bivalve (two-shelled), whole single valve, fan/disc shape
Species
Argopecten gibbus
Shell Type
Bivalve (two-shelled), whole single valve, fan/disc shape
Family
Pectinidae (Scallop family)
Size
Approximately 1 to 1.5 inches in diameter, which is average for this species. Adults typically range from 1 to 2.5 inches.
Color & Pattern
Vibrant pattern featuring concentric bands of mottled orange, peach, and reddish-brown zig-zag or flame markings interspersed with bands of creamy white. The colors are entirely natural and well-preserved with a glossy sheen.
Rarity
Common to Very Common, frequently found washed ashore along North Carolina beaches, especially after storms or rough surf.
Habitat
Shallow subtidal to moderately deep offshore waters, typically living on sandy or shelly substrates, often found in seagrass beds from the low tide mark down to depths of 160 feet.
Geographic Range
Western Atlantic Ocean, ranging from North Carolina down through Florida, the Gulf of Mexico, the Caribbean, and south to Brazil.
Description
An attractive, nearly symmetrical bivalve shell with a rounded, fan-like disc shape. It features approximately 18 to 22 well-rounded, radial ribs radiating outward from the umbo. The margins are crenulated, matching the external ribs. The surface is smooth with fine growth lines, and the striking multicolored pattern makes it a favorite among beachcombers.
Key Features
Nearly equilateral and equivalve with slightly unequal auricles (ears) at the hinge. Rounded radial ribs (usually around 20) and a distinct mottled zigzag or banded coloration pattern that separates it from plain white scallops.
Collector Value
Low to Moderate monetary value, but very high sentimental and decorative value for shell collectors and crafters. Specimens with exceptionally bright purple, pink, or deep orange coloration are particularly sought after.
Condition Notes
Good to Fine condition. The valve is structurally intact with no major chips along the delicate margins, excellent retention of original bright pigmentation, and no significant sun-bleaching or boring sponge holes.
Interesting Facts
Unlike many bivalves that burrow or remain sessile, Calico Scallops are capable of swimming short distances by rapidly clapping their valves together to expel water. They also possess dozens of simple blue eyes along the edge of their mantle that can detect light and shadow.
Ecological Role
Serves as an important prey item for various marine predators including fish, crabs, and sea stars. They are filter feeders that help clear particulate matter from the water column, contributing to water quality.
Similar Species
Atlantic Bay Scallop (Argopecten irradians), which tends to be slightly larger, flatter, and has broader, squarer ribs with fewer radial folds.
Beach Finding Tips
Best found on North Carolina outer banks beaches following a strong storm or high tide. Look near shell lines deposited on the upper beach berm where lighter bivalve shells accumulate.
Notes
NC beaches