Atlantic Calico Scallop (also known as the Calico Scallop)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: Argopecten gibbus · Pectinidae (Scallop family) · Bivalve (two-shelled), whole single valve, fan-shaped disc
Species
Argopecten gibbus
Shell Type
Bivalve (two-shelled), whole single valve, fan-shaped disc
Family
Pectinidae (Scallop family)
Size
Approximately 1.5 inches in width and length, which is average for an adult specimen of this species. Adults typically range from 1 to 2.5 inches.
Color & Pattern
This particular specimen exhibits an unusually dark, near-black or very deep charcoal coloration with subtle dark brown and purplish undertones. Typical specimens feature mottled calico patterns of red, brown, orange, yellow, and white on a cream background, making this dark morph quite distinctive and likely a result of mineral staining or natural pigment variation.
Rarity
Common (found regularly on beaches within its native range, though intensely dark color morphs are less commonly encountered).
Habitat
Found in shallow marine waters, typically ranging from low tide mark down to depths of about 160 feet (50 meters). They prefer sandy substrates, shell rubble, and occasionally seagrass beds.
Geographic Range
Western Atlantic Ocean, extending from Maryland southwards along the Florida coast, into the Gulf of Mexico, the Caribbean, and down to South America.
Description
A classic fan-shaped bivalve shell featuring prominent, rounded radial ribs (typically around 18 to 21) that radiate from the distinct, pointed umbo at the hinge. The margins are strongly scalloped, matching the external ribs. The ears (auricles) at the hinge are somewhat asymmetrical, a characteristic feature of the scallop family.
Key Features
Nearly equilateral fan shape, approximately 18 to 21 strong radial ribs, asymmetrical auricles (ears) at the hinge line, and convex valve profile.
Collector Value
Low to moderate commercial value, but highly popular among casual beachcombers and shell crafters. Unusual color morphs like this dark specimen can be of greater interest to specialized shell collectors.
Condition Notes
The shell is an intact single valve in good condition with minor natural wear along the ventral margin. The surface texture is well-preserved with no major fractures or boring marks. Collectibility grade: Good to Fine.
Interesting Facts
Scallops are among the few bivalves that can actively swim. By rapidly clapping their valves together, they expel water and propel themselves through the water column to escape predators such as starfish and carnivorous snails. They also possess dozens of tiny, bright blue eyes along the edge of their mantle that can detect light and motion.
Ecological Role
Calico scallops serve as an important food source for numerous marine predators, including fish, sea turtles, and crabs. They are filter feeders, helping to maintain water clarity by consuming phytoplankton and suspended organic particles.
Similar Species
Bay Scallop (Argopecten irradians), which tends to have slightly broader, flatter-topped ribs and fewer ribs (usually 17), and lives in shallower estuarine and seagrass habitats.
Beach Finding Tips
Look along high-tide wrack lines on sandy ocean-facing beaches, especially after storms or strong onshore winds. Snorkeling in shallow, clear sandy areas just beyond the surf line can also reveal living or freshly dead specimens.