Atlantic Calico Scallop
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: gibbus · Pectinidae (Scallop family) · Bivalve (single valve); Fan-shaped
Species
Argopecten gibbus
Shell Type
Bivalve (single valve); Fan-shaped
Family
Pectinidae (Scallop family)
Size
Approximately 1 to 1.5 inches. This is a common size for juvenile or young adult specimens; adults can reach up to 3 inches.
Color & Pattern
Mottled pattern of chocolate brown to reddish-purple splotches on a cream or white base. The coloring is arranged in distinct concentric and radial bands, often appearing as rows of squarish dots on the ribs.
Rarity
Common; one of the most frequently found decorative bivalves on the beaches of South Carolina.
Habitat
Marine; typically found in shallow to moderately deep water on sandy or silty bottoms, often associated with seagrass beds.
Geographic Range
Western Atlantic, ranging from Delaware south to Brazil, including the Gulf of Mexico and the Caribbean.
Description
A classic fan-shaped bivalve with approximately 17 to 23 radiating ribs. The shell is nearly circular except for the 'ears' or auricles at the hinge. This specimen shows the characteristically high-domed or 'gibbous' shape common to the species.
Key Features
Equilateral fan shape; radial ribs that are rounded; distinctive mottled or 'calico' color patterns; auricles (wings) that are roughly equal in size.
Collector Value
Low monetary value ($1-$5) due to high abundance, but high aesthetic value for crafts and beginner collections. Larger, perfectly matched pairs are more desirable.
Condition Notes
Good condition for a beach find. The edges show slight erosion from surf tumbling, and the colors remain vibrant despite some minor sun-bleaching. Collectibility grade: Good.
Interesting Facts
Unlike many bivalves, scallops can swim by rapidly clapping their shells together to create jet propulsion. They also have dozens of tiny, bright blue eyes along the edge of their mantle to detect motion and predators.
Ecological Role
Filter feeder that helps maintain water clarity by consuming plankton and organic detritus. They serve as a primary food source for sea stars, crabs, and rays.
Similar Species
Argopecten irradians (Bay Scallop) which is usually flatter and more somber in color (grays/blacks), and Nodipecten nodosus (Lion's Paw) which is much larger and has distinct knobs.
Beach Finding Tips
Look along the high tide line after a storm or strong onshore winds. Myrtle Beach is a hotspot for these; they are often found mixed in 'shell pockets' near the dunes.
Notes
Myrtle Beach SC