Calico Scallop (also known as the Atlantic Calico Scallop)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: A. gibbus · Pectinidae (Scallop family) · Bivalve, whole shell, fan-shaped
Species
Argopecten gibbus
Shell Type
Bivalve, whole shell, fan-shaped
Family
Pectinidae (Scallop family)
Size
Approximately 1 inch in width, which is average for this species. Adults typically range from 1 to 2.5 inches.
Color & Pattern
The specimen exhibits a heavily sun-bleached, uniform off-white to pale cream coloration. The natural mottled or zig-zag reddish-brown patterns typical of live-collected specimens have been completely faded due to weathering and sun exposure.
Rarity
Very Common, frequently found washed up on beaches throughout its native range.
Habitat
Inhabits shallow subtidal waters down to moderate depths of roughly 150 feet, typically found on sandy or shelly substrates and seagrass beds in marine environments.
Geographic Range
Western Atlantic Ocean, ranging from North Carolina through the Gulf of Mexico, the Caribbean, and down to South America.
Description
A classic fan-shaped bivalve shell featuring prominent, rounded radial ribs and a nearly symmetrical outline with characteristic small, equal-sized auricles (ears) at the hinge line. The exterior shows classic radiating costae, although weathered.
Key Features
Nearly equilateral and equivalve fan shape, distinct radial ribs (typically around 18 to 22), and well-developed symmetrical ears flanking the umbo at the hinge.
Collector Value
Low commercial or collector value due to its abundance and worn, bleached condition. It is a quintessential souvenir shell often sold in bulk in shell shops.
Condition Notes
Fair condition due to significant sun bleaching, wear on the ribs, and complete loss of original coloration. Collectibility grade is Fair to Good as a common beach find.
Interesting Facts
Scallops are unique among bivalves for their ability to swim actively by rapidly clapping their valves together to expel water, and they possess dozens of simple blue eyes along their mantle edge that can detect light and shadow.
Ecological Role
Serves as an important prey item for various marine predators including fish, rays, sea stars, and octopuses. They filter feed on phytoplankton, helping to maintain water clarity.
Similar Species
Atlantic Bay Scallop (Argopecten irradians), which tends to have fewer, broader ribs and a more northern distribution, and the Rough Scallop (Aequipecten muscosus), which has scaly ribs.
Beach Finding Tips
Look along high-tide drift lines on sandy beaches after storms, particularly in the southeastern United States and Gulf Coast, where whole valves often wash ashore in large quantities.