Calico Scallop (Sun-bleached / Fossilized appearance)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: A. gibbus · Pectinidae (Scallop family) · Bivalve (Two-shelled); Fan-shaped/Subcircular; Single valve present.
Species
Argopecten gibbus (Likely, 85% confidence)
Shell Type
Bivalve (Two-shelled); Fan-shaped/Subcircular; Single valve present.
Family
Pectinidae (Scallop family)
Size
Approximately 2.5 inches in diameter. This is a mature specimen; typical adult range for the species is 1 to 3 inches.
Color & Pattern
Dull cream to off-white base color. The original 'calico' pattern (mottled pink, purple, or orange) has been lost due to weathering or fossilization. No original periostracum is visible; the texture is matte and chalky.
Rarity
Common. These shells are frequently washed up on beaches, though finding one in this thick, weathered condition often points to it being from a quaternary deposit or an older beach ledge.
Habitat
Typically found in marine environments, specifically on sandy or gravelly bottoms in offshore waters at depths of 30 to 1,200 feet.
Geographic Range
Western Atlantic, from North Carolina to Brazil, including the Gulf of Mexico and the Caribbean Sea.
Description
A robust, fan-shaped bivalve with roughly 19 to 21 radiating ribs. The shell is equilateral and heavily calcified. The ribs are rounded and well-defined near the umbo (beak), gradually widening toward the margin. The ears (auricles) appear balanced, though slightly worn.
Key Features
Equal valves (nearly identical in curvature), distinctive deep radiating ribs that lack prominent spines, and a circular outline with small 'ears' at the hinge.
Collector Value
Low. While a classic beach find, its lack of original color and the presence of weathering makes it more of a 'souvenir' piece than a high-end collector specimen. Approximate value: $1-$3 USD.
Condition Notes
Fair to Good. The shell shows significant weathering and 'chalkiness,' suggesting it has spent considerable time exposed to the elements or buried. There is minor chipping on the posterior margin and loss of all original pigmentation.
Interesting Facts
Unlike many bivalves, Calico Scallops can swim short distances by rapidly opening and closing their valves, creating a jet-propulsion effect to escape predators like sea stars.
Ecological Role
As filter feeders, they strain plankton from the water column. They serve as a vital food source for crabs, octopuses, and bottom-dwelling fish.
Similar Species
Argopecten irradians (Bay Scallop) which has fewer ribs and is usually flatter, or Nodipecten nodosus (Lion's Paw), which is much larger with distinct knobs.
Beach Finding Tips
Look along the high-tide line after winter storms on Atlantic-facing beaches. These thicker, whitened valves are often found embedded in shell-hash layers further back from the water.