Calico Clam (also known as the Calico Scallop or young Ark Shell depending on region, but features match a small subglobose bivalve variant)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: A. gibbus · Pectinidae (Scallop family) · Bivalve (two-shelled clam/scallop), whole shell, fan to subglobose shape
Species
Argopecten gibbus
Shell Type
Bivalve (two-shelled clam/scallop), whole shell, fan to subglobose shape
Family
Pectinidae (Scallop family)
Size
Approximately 1 to 1.5 inches in width and length. This is typical for a juvenile or small adult specimen, with maximum species potential reaching up to 3 inches.
Color & Pattern
Pale cream to light tan base with soft yellowish-orange tinges concentrated near the umbo. The coloration appears somewhat weathered and sun-bleached from exposure, typical of a beach-washed specimen.
Rarity
Common, frequently found washed ashore along southeastern US and Gulf of Mexico beaches.
Habitat
Found in shallow marine waters, primarily in sandy or shelly substrates, often associated with seagrass beds in the subtidal zone.
Geographic Range
Western Atlantic Ocean, ranging from North Carolina down through the Gulf of Mexico, the Caribbean, and south to Brazil.
Description
A compact, rounded bivalve featuring prominent concentric growth rings radiating outward from a distinct, slightly off-center umbo. The exterior texture exhibits fine ridges following the growth lines, giving it a tactile, stepped appearance.
Key Features
Rounded contour with a prominent, smooth, yellowish beak (umbo) and strong, regular concentric growth lines rather than the sharp radial ribs typical of many classic fan-shaped scallops.
Collector Value
Low to moderate commercial value. While abundantly collected as souvenirs and used in craft projects, perfectly matched gem-quality pairs hold minor appeal for casual beachcombers.
Condition Notes
Fair to Good condition. The shell is structurally intact with some surface wear and sun-bleaching. The margins show minor natural weathering typical of beach collection. Collectibility grade is Good.
Interesting Facts
Scallops are among the few bivalves that can actively swim by rapidly clapping their valves together to expel water, utilizing a series of simple blue eyes along their mantle edge to detect motion.
Ecological Role
Serves as an important prey species for various marine carnivores including fish, sea stars, and octopuses, contributing to the benthic marine food web.
Similar Species
Atlantic Bay Scallop (Argopecten irradians), which typically features more pronounced radial ribs rather than dominant concentric rings.
Beach Finding Tips
Look along high-tide wrack lines on sandy ocean-facing beaches, especially after storms or heavy winds in the southeastern United States and Florida.