Atlantic Bay Scallop
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Argopecten, Species: Argopecten irradians · Pectinidae (Scallop family) · Bivalve (two-shelled). This specimen is a single valve (either left or right) with a fan-like shape.
Species
Argopecten irradians (Confidence: 95%)
Shell Type
Bivalve (two-shelled). This specimen is a single valve (either left or right) with a fan-like shape.
Family
Pectinidae (Scallop family)
Size
Approximately 1 to 1.5 inches. This is a juvenile to sub-adult specimen; adults typically reach 3 inches.
Color & Pattern
Mottled pattern with dark brown and reddish-purple bands over a cream-to-gray base. Notable 'zigzag' or 'chevron' markings on the ribs. The color appears natural and well-preserved.
Rarity
Common. They are frequently washed up on Atlantic beaches, though finding a perfectly intact pair (both valves) is less common.
Habitat
Marine; primarily found in shallow subtidal waters, especially in seagrass beds (eelgrass) and sandy or muddy bottoms in bays and estuaries.
Geographic Range
Western Atlantic, ranging from Cape Cod to Florida and the Gulf of Mexico. This specimen from Holden Beach, NC, is perfectly within its core range.
Description
An attractive, symmetrical fan-shaped bivalve featuring 17–22 radiating ribs. The 'ears' (auricles) at the hinge are nearly equal in size, a hallmark of the Argopecten genus. The surface has a slightly rough texture due to concentric growth lines crossing the ribs.
Key Features
Nearly equilateral triangular auricles (wings), 17-22 rounded ribs, and a distinct mottled color pattern. Unlike the Calico Scallop, the ribs of the Bay Scallop are usually more distinct and the shell is slightly flatter.
Collector Value
Low to Moderate. While common, specimens with vivid patterns or paired valves are favorites for 'beach treasures' and craft displays. Commercially, they are highly valued for their edible adductor muscle.
Condition Notes
Good to Fine. The coloration is vibrant and the edges are largely intact, though the hinge shows minor wear. The absence of heavy bleaching suggests it was not exposed to the sun for long.
Interesting Facts
Living bay scallops have 30 to 40 bright blue eyes along the edge of their mantle that can detect movement and light. They are also unique among bivalves for their ability to 'swim' by rapidly snapping their shells shut to expel water.
Ecological Role
Filter feeders that help improve water clarity by consuming plankton. They are a vital food source for crabs, sea stars, and whelks. They are indicators of healthy seagrass ecosystems.
Similar Species
Argopecten gibbus (Calico Scallop) which has more intense spotting and occurs in deeper water; and Placopecten magellanicus (Atlantic Sea Scallop) which is much larger and smoother.
Beach Finding Tips
Best found after storms or high tides at Holden Beach. Search the wrack line (seaweed piles) where smaller, lighter shells like these get trapped. Look in the shallow pools left at low tide.
Notes
Holden Beach, NC