Broad-ribbed Cardita / Amradi
Phylum: Mollusca, Class: Bivalvia, Order: Carditida, Family: Carditidae, Genus: Cardita, Species: Cardita borealis · Carditidae (Cardita family) · Bivalve (two-shelled), whole shell, fan/heart shape
Species
Cardita borealis
Shell Type
Bivalve (two-shelled), whole shell, fan/heart shape
Family
Carditidae (Cardita family)
Size
Approximately 1 inch, typical for this species which generally ranges from 0.75 to 1.5 inches.
Color & Pattern
Rich reddish-brown or chestnut alternating with stark white or cream radial ribs. The coloration is completely natural and vibrant, showing high contrast between the broad radial ribs and interspaces.
Rarity
Common in its northern range, but an uncommon and delightful beach find further south along North Carolina beaches.
Habitat
Shallow subtidal to deep cold waters, typically found attached by byssus threads to hard substrates like rocks, shells, or gravel in marine environments.
Geographic Range
Western Atlantic from the Arctic down to North Carolina, frequently encountered in northern New England and occasionally washing ashore on mid-Atlantic beaches.
Description
A solid, robust, somewhat heart-shaped bivalve featuring prominent, rounded radial ribs that create a deeply scalloped and wavy margin. The exterior surface displays a striking pattern of contrasting warm brown and white bands radiating from the umbo.
Key Features
Heavy, thick-shelled construction with 10 to 18 prominent, rounded radial ribs, an inflated profile, and a distinctively scalloped ventral margin.
Collector Value
Low to moderate commercial value, but highly valued by regional beachcombers and shell enthusiasts as a pristine display of cold-water bivalve geometry.
Condition Notes
Good to Fine condition. The specimen appears intact with strong natural coloration, minimal erosion, and clear radial ribs, representing a very collectible beach-worn or drift specimen.
Interesting Facts
Carditas are suspension feeders that use strong byssus threads to anchor themselves firmly to hard surfaces in high-energy marine environments, resisting strong wave action.
Ecological Role
Acts as an important filter feeder helping to clear suspended organic particles from the water column, and serves as a micro-habitat and food source for various marine predators.
Similar Species
Trapezium shells or other smaller ark shells, but Cardita can be easily distinguished by its heavy, rounded, and fewer radial ribs with high-contrast color banding.
Beach Finding Tips
Look along shell lines after storms or high tides, particularly on beaches with mixed sand and gravel substrates or near jetties and rocky outcroppings.
Notes
NC beaches