Atlantic Calico Scallop (commonly referred to as the Calico Scallop)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: A. gibbus · Pectinidae (Scallop family) · Bivalve (Two-shelled); This specimen is a single valve (half-shell) with a fan-shaped morphology.
Species
Argopecten gibbus
Shell Type
Bivalve (Two-shelled); This specimen is a single valve (half-shell) with a fan-shaped morphology.
Family
Pectinidae (Scallop family)
Size
Approximately 1 inch (25mm) in width. This is a juvenile specimen; adults typically range from 1 to 3 inches.
Color & Pattern
Mottled pattern of reddish-brown streaks and rectangular blotches against a creamy white or pale yellow base. The colors appear natural and fairly vibrant, though slightly softened by water action. Interior is typically white with color showing through the thin shell.
Rarity
Very Common; one of the most frequently found shells on Myrtle Beach and throughout the Carolinas.
Habitat
Marine; found in shallow subtidal waters and offshore on sandy or shelly substrates. They are commonly associated with seagrass beds and open sandy bottoms.
Geographic Range
Western Atlantic from North Carolina to Brazil, including the Gulf of Mexico and the Caribbean. Specifically common along the South Carolina and Florida coastlines.
Description
A classic fan-shaped bivalve with roughly 19 to 22 radiating ribs. The shell is equilateral and moderately inflated. The 'ears' (auricles) at the hinge are nearly equal in size, which is a characteristic of the Argopecten genus. The surface texture is relatively smooth between ribs but shows fine concentric growth lines.
Key Features
Distinctive 'calico' mottled color pattern, equal-sized auricles (wings) at the hinge, and roughly 20 rounded radial ribs. Unlike the Bay Scallop, the valves are more inflated (convex).
Collector Value
Low monetary value due to its abundance, though highly prized by casual beachcombers for its beautiful and varied color patterns. Exceptional specimens with deep purple or bright orange hues are more desirable.
Condition Notes
Good condition. The shell appears intact with no major chips on the fragile edges. There is minor surf-wear (smoothing of the ribs) and slight fading from exposure, but the primary patterns remain distinct. Collectibility Grade: Fine.
Interesting Facts
Unlike many bivalves, Calico Scallops can swim by rapidly snapping their shells together to create jet propulsion. They also possess dozens of tiny, bright blue eyes along the edge of their mantle that can detect movement and light changes.
Ecological Role
Filter feeders that help clear the water of plankton and organic debris. They are a vital food source for sea stars, crabs, and various shorebirds. They are also harvested commercially for their 'scallop meat' (the large adductor muscle).
Similar Species
Argopecten irradians (Bay Scallop) which is usually flatter and typically darker (gray/brown) rather than mottled; and Nodipecten nodosus (Lion's Paw) which is much larger and has heavy knobs on the ribs.
Beach Finding Tips
Best found at low tide after a storm or strong onshore winds. Look in the 'shell hash' lines where small bivalves accumulate. Myrtle Beach is a prime location for these after high tide cycles.
Notes
Myrtle Beach SC