Ocean Quahog (also known as Mahogany Clam, Black Clam, or Icelandic Cyprina)
Phylum: Mollusca, Class: Bivalvia, Order: Venerida, Family: Arcticidae, Genus: Arctica, Species: Arctica islandica · Arcticidae (Ocean Quahog family) · Bivalve (two-shelled clam), whole single valve, fan/oval shape
Species
Arctica islandica
Shell Type
Bivalve (two-shelled clam), whole single valve, fan/oval shape
Family
Arcticidae (Ocean Quahog family)
Size
Approximately 2.5 to 3 inches in width, which is a medium-sized adult specimen. Adults typically range from 2 to 4 inches (5 to 10 cm), though this species is famous for reaching exceptional sizes over long lifespans.
Color & Pattern
The exterior exhibits a creamy white or pale yellowish-brown base with concentric growth lines, heavily stained with reddish-orange iron oxide from the distinct red sandstone beaches of Prince Edward Island. In living specimens, the shell is covered by a thick, dark brown to black periostracum, which has worn away here, revealing the natural lighter calcareous layer underneath stained by local sediments.
Rarity
Very Common. This is a very common species along the Atlantic coast of Canada and the northeastern United States, regularly washed ashore on beaches, especially after storms.
Habitat
Marine benthic environment, typically found burrowed in fine sand, muddy sand, or soft mud substrates in cold, subarctic to temperate waters, ranging from shallow subtidal zones down to depths of over 400 meters.
Geographic Range
North Atlantic Ocean, found on both North American coasts from Newfoundland down to Cape Hatteras, and European coasts from Iceland and Norway down to the Bay of Biscay.
Description
A sturdy, heavy, rounded-triangular bivalve shell with prominent, slightly anteriorly directed umbones. The exterior surface features fine, regular concentric growth rings marking the animal's life stages. This particular specimen displays a warm, reddish-orange patina acquired from the iron-rich sandstone and clay formations characteristic of Prince Edward Island's famous red beaches.
Key Features
Rounded-oval to triangular profile, heavy and solid construction, prominent forward-pointing beaks (umbones), absence of a pallial sinus, and a strong internal hinge structure characteristic of the Arcticidae family.
Collector Value
Low monetary value, as they are extremely abundant commercially and in the wild. However, this specimen has high sentimental and aesthetic value for a beachcomber due to the striking natural red-ochre iron stain unique to Prince Edward Island shores.
Condition Notes
Good condition. It is a solid, intact single valve with minor natural weathering and staining from its environment. The margins are relatively smooth with slight wear, and there are no major fractures or predator boring holes. Graded as Good to Fine for a beach-collected specimen.
Interesting Facts
Arctica islandica is famous for being one of the longest-living animals on Earth. Individual specimens have been scientifically documented to live for over 500 years, making them invaluable for climate research as their shell growth rings function much like tree rings to record historical ocean temperatures.
Ecological Role
A vital benthic filter feeder that processes large volumes of seawater, removing suspended organic matter and phytoplankton. It serves as a major food source for various bottom-feeding fish, crabs, and sea stars, and supports commercial fisheries in certain regions.
Similar Species
Hard Shell Clam or Northern Quahog (Mercenaria mercenaria), which can be distinguished by a prominent pallial sinus inside the shell and a more centrally located umbo, as well as distinct purple markings on the interior margin.
Beach Finding Tips
Look along the tide lines of sandy or mixed sediment beaches in Atlantic Canada, particularly after heavy winds or storms. On Prince Edward Island, scanning the red sand beaches at low tide often reveals single valves washed up from offshore beds.
Notes
I found this shell in Prince Edward Island, at a red beach, what rarity is it, is it good or worth it?