Atlantic Bay Scallop
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: Argopecten irradians · Pectinidae (Scallop family) · Bivalve; specifically a single valve (either left or right). Shape: Fan-shaped / subcircular with distinct auricles (ears) at the hinge.
Species
Argopecten irradians
Shell Type
Bivalve; specifically a single valve (either left or right). Shape: Fan-shaped / subcircular with distinct auricles (ears) at the hinge.
Family
Pectinidae (Scallop family)
Size
Approximately 1.5 to 2.5 inches in diameter. This specimen appears to be an average adult size; the species typically reaches max 3 inches.
Color & Pattern
Exhibits a mottled base of gray and white with striking reddish-brown and purplish radial bands. The ribs show darker pigmentation than the grooves. Colors appear somewhat weathered/beach-worn but retain natural pigments. Interior is likely white with a purplish tint near the hinge hinge.
Rarity
Common. These are frequently found on beaches after storms or at low tide in their native range.
Habitat
Found in shallow marine waters, particularly in seagrass beds (Zostera marina) and sandy/muddy bottoms. Common in estuaries and protected bays.
Geographic Range
Western Atlantic coast, ranging from Cape Cod, Massachusetts, down to the Gulf of Mexico and the Caribbean, with various subspecies depending on the specific region.
Description
A classic fan-shaped bivalve featuring approximately 17 to 22 well-defined radial ribs. The shell is nearly circular except for the squared-off auricles at the hinge. The texture is slightly rough due to growth lines crossing the ribs. The valves are moderately inflated, with the lower valve typically being lighter in color than the upper valve.
Key Features
Distinctive symmetrical 'ears' at the base; 17-22 rounded ribs; deep purple-brown splotches; lack of spines; relatively thin compared to the thicker Calico Scallop.
Collector Value
Minimal monetary value (typically $1-$5) due to high abundance, but high aesthetic value for thematic collections. Deep purple or vibrant orange variants are more prized by hobbyists.
Condition Notes
Fair to Good. The edges show some minor chipping and beach-wear (erosion). The color is still vibrant but dulled by exposure. No visible boring holes from predatory snails, making it a decent educational specimen. Grade: Fine.
Interesting Facts
Unlike many bivalves, the living animal can swim by rapidly clapping its valves together to create jet propulsion. They also possess up to 100 bright blue eyes located along the edge of their mantle to detect motion and shadows of predators.
Ecological Role
Filter feeders that improve water quality by removing plankton and organic matter. They are a vital food source for sea stars, crabs, and rays. The species is also a commercially important fishery.
Similar Species
Calico Scallop (Argopecten gibbus) which is usually more mottled/spotted and prefers deeper offshore water; Rough Scallop (Aequipecten muscosus) which has small scales or spines on the ribs.
Beach Finding Tips
Search the wrack line after a strong onshore wind or storm. They are often found caught in clumps of seaweed or washed up in sandy coves within tidal estuaries.