Calico Scallop
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: Argopecten gibbus · Pectinidae (Scallop family) · Bivalve (Fan-shaped single valve)
Species
Argopecten gibbus (Confidence: 95%)
Shell Type
Bivalve (Fan-shaped single valve)
Family
Pectinidae (Scallop family)
Size
Approximately 1.5 to 2 inches (38-50mm). This is typical for a mid-sized adult, as the species generally ranges from 1 to 3 inches.
Color & Pattern
Mottled pattern with dark mahogany or reddish-brown concentric bands and blotches over a cream/tan base. The pattern is vivid and appears natural rather than sun-bleached. The ribs show alternating light and dark pigmentation typical of the 'calico' name.
Rarity
Very Common. This is one of the most frequently found shells on Southeast US and Gulf coast beaches.
Habitat
Found in marine environments, specifically on sandy or shelly sea floors. They typically live in open water at depths ranging from 60 to 130 feet, though they are frequently washed into the intertidal zone.
Geographic Range
Western Atlantic, ranging from North Carolina south through the Gulf of Mexico and the Caribbean to Brazil.
Description
A classic fan-shaped bivalve featuring approximately 17 to 22 radiating ribs. The shell has a distinctive 'inflated' or puffed appearance (gibbous) rather than being flat. It features two 'wings' (auricles) at the hinge line. The surface is textured by the ribs, which are rounded and prominent.
Key Features
Distinctive mottled/calico color pattern, approximately 20 rounded radiating ribs, and an equidistant hinge line with nearly symmetrical auricles. The inflation of the valve is greater than that of the similar Bay Scallop.
Collector Value
Low monetary value ($1-$5) due to high abundance, but highly desirable for craft enthusiasts and beginner collectors because of the infinite variety of beautiful color patterns.
Condition Notes
Good to Fine condition. The shell maintains its natural luster and sharp color definition. The margins appear slightly worn from wave action, and it is a single valve rather than a paired living specimen.
Interesting Facts
Unlike many bivalves, Calico Scallops can swim by rapidly snapping their shells together to create jet propulsion. They have dozens of tiny, bright blue eyes along the edge of their mantle that can detect movement and light changes.
Ecological Role
They are filter feeders, consuming plankton and organic detritus, which helps clear the water. They are a primary food source for sea stars, crabs, and octopuses.
Similar Species
Argopecten irradians (Bay Scallop) which is usually drabber (grey/brown) and flatter, and Nodipecten nodosus (Lion's Paw) which is much larger with heavy knobs.
Beach Finding Tips
Best found after storms or high winds on Florida and Gulf Coast beaches. Look in the 'shell hash' at the high tide line. They are often found in great numbers at Sanibel Island.