Atlantic Bay Scallop
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: Argopecten irradians · Pectinidae (Scallop family) · Bivalve (fan-shaped single valve)
Species
Argopecten irradians
Shell Type
Bivalve (fan-shaped single valve)
Family
Pectinidae (Scallop family)
Size
Approximately 1.5 to 2 inches (38-50mm). This is a juvenile to mid-sized specimen, as adults typically reach 3 inches.
Color & Pattern
Deep purplish-brown and reddish-mottled exterior with distinct concentric banding. The pigmentation shows white flecks and 'peppered' highlights across the radial ribs. The interior (unseen but characteristic) is usually white with purple staining near the hinge.
Rarity
Common (found regularly on beaches, especially after storms in the Carolinas).
Habitat
Shallow marine waters, specifically seagrass beds (eelgrass), sandy bottoms, and salt marshes. They prefer subtidal zones but are often washed into the intertidal zone.
Geographic Range
Western Atlantic coast, ranging from Cape Cod, Massachusetts to the Gulf of Mexico and into the Caribbean.
Description
An elegant, fan-shaped bivalve featuring approximately 17 to 22 radiating ribs. The shell is nearly equilateral with two distinct 'ears' or auricles at the hinge. The texture is finely ribbed with a slightly convex profile, exhibiting the classic decorative symmetry associated with the scallop family.
Key Features
Equilateral fan shape, 17-22 prominent radial ribs that are square-shaped in cross-section rather than rounded, and nearly equal-sized 'ears' (auricles) on either side of the umbo.
Collector Value
Low to Moderate. While very common, specimens with deep purple or bright orange coloration are highly desired for aesthetic displays. A complete, matching 'paired' set is worth significantly more than a single valve.
Condition Notes
Good to Fine. The shell maintains excellent pigmentation and crisp ribbing. There is slight beach-wear on the margins (edges) and some fading typical of a beach-found specimen. It appears to be a single valve (either left or right) rather than a complete hinged pair.
Interesting Facts
Unlike most bivalves, the living animal has dozens of bright blue eyes located along the edge of its mantle to detect movement. They are also unique for their ability to 'swim' by rapidly clapping their shells together to create jet propulsion.
Ecological Role
Filter feeder that improves water quality by straining plankton and organic matter. They are a vital food source for sea stars, crabs, and rays. Local populations are sensitive to water quality and seagrass habitat loss.
Similar Species
Calico Scallop (Argopecten gibbus), which is usually more mottled and occurs in deeper water; and the Rough Scallop (Aequipecten muscosus), which has small scales or spines on the ribs.
Beach Finding Tips
In Myrtle Beach, look along the high-tide line (the wrack line) after a strong offshore wind or storm. They are often found mixed in with shell hash and seaweed debris.
Notes
Myrtle Beach SC