Atlantic Calico Scallop
Kingdom: Animalia, Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: A. gibbus · Pectinidae (Scallop family) · Bivalve (single valve shown); Fan-shaped
Species
Argopecten gibbus
Shell Type
Bivalve (single valve shown); Fan-shaped
Family
Pectinidae (Scallop family)
Size
Approximately 1.5 to 2 inches (38-50mm). This is typical for a mature specimen; the species generally caps at around 3 inches.
Color & Pattern
Mottled pattern of reddish-brown and deep mahogany on a cream-to-white base. Features distinct zig-zag or 'calico' banding across approximately 19-22 radiating ribs. The colors appear natural but slightly weathered by the surf.
Rarity
Very Common; it is one of the most frequently found shells on North Carolina beaches like Holden Beach.
Habitat
Marine; typically found in open-shelf waters on sandy or shelly substrates at depths ranging from 10 to 400 feet.
Geographic Range
Western Atlantic, ranging from Delaware south to Brazil, very common in the Gulf of Mexico and coastal waters of the Southeastern United States, including North Carolina.
Description
A classic fan-shaped bivalve with roughly equal-sized 'ears' (auricles) at the hinge. The exterior surface is characterized by prominent radiating ribs that give the shell a corrugated appearance. This specific specimen shows the upper (top) valve, which is more vibrantly colored than the typically whiter lower valve.
Key Features
Symmetrical fan shape, roughly 20 rounded radiating ribs, and the distinct mottled/calico color pattern. Unlike the Bay Scallop, the Calico Scallop is more circular and the ears are nearly identical in size.
Collector Value
Low; primarily valued for its aesthetic beauty and use in crafts. While not a high-priced rarity, it is a quintessential 'treasure' for beachcombers due to its variety of color patterns.
Condition Notes
Good. The valve is largely intact with clear ribbing and pattern, though it shows typical beach wear (minor erosion on the margin and hinge area). No obvious boring holes from predatory snails.
Interesting Facts
Unlike most mollusks, scallops have dozens of tiny, bright blue eyes along the edge of their mantle to detect motion. They are also unique among bivalves for their ability to 'swim' by rapidly clapping their valves together to create jet propulsion.
Ecological Role
Suspension feeders that filter plankton from the water column. They are an important food source for sea stars, crabs, and rays. The species is also commercially harvested for its large adductor muscle.
Similar Species
Argopecten irradians (Bay Scallop), which is usually more drab, greyish-brown, and has a flatter profile compared to the more 'inflated' or convex shell of the Calico Scallop.
Beach Finding Tips
Best found after storms or during low tide at Holden Beach. Look in the 'wash' line where the tide deposits smaller shells. They are more abundant in the winter months when colder water currents bring them closer to shore.
Notes
Holden Beach, NC