Atlantic Giant Scallop (also known as the Sea Scallop)
Phylum: Mollusca, Class: Bivalvia, Order: Pectinida, Family: Pectinidae, Genus: Placopecten, Species: Placopecten magellanicus · Pectinidae (Scallop family) · Bivalve (Two-shelled); Fan-shaped; Upper (left) valve only
Species
Placopecten magellanicus
Shell Type
Bivalve (Two-shelled); Fan-shaped; Upper (left) valve only
Family
Pectinidae (Scallop family)
Size
Approximately 4.5 to 5 inches (11-13 cm). This is a mature adult, as the species typically ranges from 4 to 8 inches.
Color & Pattern
The exterior displays a reddish-pink to mauve-brown color with subtle radiating bands. The color fades toward the 'ears' (auricles) near the hinge. It features a pattern of concentrically arranged growth lines overlapping fine radiating ribs. The interior (visible at the edges) is a glossy, creamy white.
Rarity
Common. These are frequently found as single valves on beaches after storms and are commercially abundant as a food source.
Habitat
Benthic marine environment; found on sand, gravel, and mixed substrates in cold temperate waters. They typically occur at depths ranging from 10 to 100 meters, though they can be found as deep as 300 meters.
Geographic Range
Northwest Atlantic Ocean, ranging from the north coast of Newfoundland to Cape Hatteras, North Carolina.
Description
A large, elegant fan-shaped shell with a relatively flat top valve. The surface is characterized by very fine, numerous radiating striae (ribs) that are crossed by concentric growth rings, giving it a texture that feels slightly rough like fine sandpaper. The 'ears' or auricles at the hinge are nearly equal in size, which is a key identification trait for this genus.
Key Features
Large rounded fan shape; nearly symmetrical auricles (ears); reddish-purple upper valve pigmentation; fine, non-prominent radiating ribs; generally flatter profile compared to 'bay' scallops.
Collector Value
Low to Moderate. While beautiful and popular for crafts or home decor, they are very common. A 'Gem' grade specimen with both valves intact and the hinge ligament preserved is more desirable to serious collectors.
Condition Notes
Fine condition. The edges show minor chipping (typical of beach-worn specimens), but the central disk and color are well-preserved. There is no evidence of predation holes, and the shell retains its natural matte luster.
Interesting Facts
Unlike many other bivalves, these scallops are active swimmers; they can 'fly' through the water by rapidly snapping their valves together to eject water. They have dozens of tiny, bright blue eyes along the edge of their mantle that can detect movement and light changes.
Ecological Role
Filter feeders that help maintain water clarity by consuming phytoplankton. They provide a substrate for tube worms and bryozoans on their shells and are a primary food source for sea stars, crabs, and humans.
Similar Species
Argopecten irradians (Atlantic Bay Scallop) which is smaller with much deeper, more prominent ribs; or Pecten maximus (Great Scallop) found in Europe which has a much deeper lower valve.
Beach Finding Tips
Best found on Atlantic beaches after a strong Nor'easter or winter storm. Look along the high-tide line among kelp and debris. In the southern part of its range (NC/VA), they are more common on offshore sandbars reachable at very low spring tides.