Atlantic Blue Mussel (also known as the Edible Blue Mussel or Common Mussel)
Phylum: Mollusca, Class: Bivalvia, Order: Mytilida, Family: Mytilidae, Genus: Mytilus, Species: M. edulis · Mytilidae (Mussel family) · Bivalve (two-shelled), specifically a fragment/valve showing the distinctive iridescent interior nacre and hinge area.
Species
Mytilus edulis
Shell Type
Bivalve (two-shelled), specifically a fragment/valve showing the distinctive iridescent interior nacre and hinge area.
Family
Mytilidae (Mussel family)
Size
The visible piece is approximately 1 to 1.5 inches across, representing a fragment of a typical adult specimen which usually ranges between 2 to 4 inches in total length.
Color & Pattern
The interior features a stunning, deep navy blue to purplish-blue nacre with a pearlescent, silvery-white muscle scar area near the apex. The exterior, partially visible or implied by the species, is typically a dark blue, violet, or dark brown.
Rarity
Very Common. Mussels are abundant in their natural intertidal zones and their shells or shell fragments are frequently washed ashore.
Habitat
Found in intertidal and shallow subtidal marine environments, attached securely to hard substrates such as rocks, pier pilings, and shell beds using tough proteinaceous threads called byssus.
Geographic Range
Widespread in cold and temperate coastal waters of the Northern Hemisphere, including the North Atlantic coasts of North America and Europe.
Description
This specimen is a fragment of a bivalve shell displaying the smooth, deep blue interior characteristic of the family Mytilidae. The surface is lustrous, showing smooth concentric growth lines on the interior nacre and a strong, pointed umbo area where the two valves hinge together.
Key Features
Distinguished by an elongated wedge shape in complete specimens, a terminal umbo at the sharpest point, and a strikingly dark blue to purple inner nacre with a distinct pearly appearance.
Collector Value
Low commercial or collector value due to their extreme abundance and the fragmentary nature of this specific piece, though they are popular for educational displays and crafts.
Condition Notes
This is a shell fragment consisting of the umbo and hinge region of a single valve. It is worn at the edges but retains its vibrant blue nacre coloration. Collectibility grade is Fair due to it being a fragment rather than a whole, intact specimen.
Interesting Facts
Blue mussels are heavily farmed for human consumption around the world. They secrete strong byssus threads—often called 'beard'—that allow them to withstand pounding wave action on rocky shores.
Ecological Role
Blue mussels are crucial filter feeders that help clean coastal waters by removing suspended particles and phytoplankton. They also form dense mussel beds that provide complex habitats and shelter for numerous other intertidal organisms.
Similar Species
California Mussel (Mytilus californianus) which is generally larger with heavier radial ribs, and the Mediterranean Mussel (Mytilus galloprovincialis).
Beach Finding Tips
Look along rocky shorelines, jetties, and sandy beaches near rocky outcroppings after storms or during low tide, where fragments and whole shells frequently wash ashore.