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 (Confidence: 95%)
Shell Type
Bivalve (Fan-shaped single valve)
Family
Pectinidae (Scallop family)
Size
Approximately 1.5 to 2 inches (38-50mm). This is a medium-sized specimen; adults typically reach 3 inches.
Color & Pattern
Mottled reddish-brown and tan exterior with subtle concentric banding. The ribs show lighter highlights against darker recessed grooves. The interior is likely white or grayish with a darker purple/brown stain near the hinge (typical of the species).
Rarity
Common (Regularly found on North Carolina beaches after storms or high tides).
Habitat
Shallow marine waters, specifically seagrass beds (Zostera marina) and sandy/muddy bottoms in protected bays and sounds.
Geographic Range
Western Atlantic from Cape Cod to the Gulf of Mexico. This specimen from Holden Beach, NC, is in the heart of its natural range.
Description
A classic fan-shaped bivalve with roughly 17 to 22 radiating ribs. The shell is nearly circular except for the 'ears' (auricles) at the hinge. The ribs are rounded and the overall texture is slightly rough due to growth lines crossing the ribs.
Key Features
Symmetrical fan shape, distinctive ribbed sculpture, and nearly equal-sized 'ears' (auricles) at the hinge which distinguish it from the zigzag scallop or calico scallop.
Collector Value
Low monetary value ($1-$5) due to its abundance, but highly desirable for craft enthusiasts and regional collectors due to its iconic shape and pleasing color variations.
Condition Notes
Good condition. The valve is fully intact with minimal beach-wear on the edges. The color remains vibrant, suggesting it was not exposed to the sun for an extended period. Grading: Fine.
Interesting Facts
Bay scallops are unique because they have up to 40 bright blue eyes along the edge of their mantle to detect predators. They are also famous for their ability to 'swim' by rapidly clapping their valves together to create jet propulsion.
Ecological Role
Filter feeder that helps clear the water of plankton. They are a vital food source for crabs, sea stars, and whelks. Population health is often used as an indicator of seagrass meadow health.
Similar Species
Calico Scallop (Argopecten gibbus) which is usually more mottled with bright pink/purple and has a more 'inflated' or convex shell.
Beach Finding Tips
Look along the wrack line after a central NC storm. They are often found mixed with eelgrass debris. Holden Beach is an excellent spot for these, especially near the inlets.
Notes
Holden Beach, NC