Calico Clam (also known as the Broad-ribbed Cardita)
Phylum: Mollusca, Class: Bivalvia, Order: Carditida, Family: Carditidae, Genus: Carditamera, Species: Carditamera floridana · Carditidae (Cardita family) · Bivalve, specifically a heavily worn or tumbled fragment/hinge area of a valve with a heart-like shape.
Species
Carditamera floridana
Shell Type
Bivalve, specifically a heavily worn or tumbled fragment/hinge area of a valve with a heart-like shape.
Family
Carditidae (Cardita family)
Size
Approximately 1 inch across, which is typical for a fragment of this species. Complete adults typically range from 1 to 1.5 inches.
Color & Pattern
Milky white base with subtle brownish-gray concentric banding and growth lines, heavily water-worn and sun-bleached due to beach tumbling.
Rarity
Common
Habitat
Found in shallow marine waters, typically living attached by a strong byssus to hard substrates, rocks, or shells in sandy-muddy environments.
Geographic Range
Western Atlantic, specifically from North Carolina down through Florida and the Gulf of Mexico, extending into the Caribbean.
Description
This specimen is a charming, heart-shaped shell fragment that has been smoothed down by wave action into a pebble-like form. While the original radiating ribs and robust hinge have been heavily eroded, the concentric growth rings and characteristic heart silhouette remain clearly visible, giving it a unique tumbled appeal.
Key Features
Heart-shaped profile, robust cardinal teeth area, and concentric banding lines visible on a heavily worn surface.
Collector Value
Low collector value in monetary terms, but highly valued by casual beachcombers for its pleasing heart-like shape and smooth, tactile feel.
Condition Notes
Fair condition as a beach-tumbled fragment. It is entirely worn down with no original periostracum or sharp ridges remaining, but it has high tactile appeal as a beach pebble.
Interesting Facts
Carditid bivalves use a strong byssus thread to anchor themselves permanently to hard surfaces, allowing them to withstand heavy wave action in the intertidal and shallow sub-tidal zones.
Ecological Role
As suspension feeders, Carditid clams filter organic particles from the water column, helping to clear water and cycle nutrients in benthic marine habitats.
Similar Species
Other small bivalve fragments from families like Veneridae or Lucinidae, distinguished by different hinge structures and lack of the thick, heart-shaped carditid profile.
Beach Finding Tips
Look in the high-tide shell lines on sandy-shelly beaches, particularly after storm events when heavier wave action deposits tumbled shell fragments and pebbles.
Notes
Outer banks, North Carolina on Kill Devils Hill beach