Linga Clam (also known as the Glen-rose Shell or Cross-hatched Lucine)
Phylum: Mollusca, Class: Bivalvia, Order: Lucinida, Family: Lucinidae, Genus: Linga, Species: L. pensylvanica · Lucinidae (Lucine Clams) · Bivalve (Two-shelled); this specimen is a single valve. Shape is sub-globular, thick, and inflated (heart-shaped when both valves are together).
Species
Linga pensylvanica (95% confidence based on bulbous shape and typical concentric ridge pattern)
Shell Type
Bivalve (Two-shelled); this specimen is a single valve. Shape is sub-globular, thick, and inflated (heart-shaped when both valves are together).
Family
Lucinidae (Lucine Clams)
Size
Approximately 1.5 to 2 inches in length. This is a mature specimen; typical adult range for this species is 1 to 2.5 inches.
Color & Pattern
Uniformly creamy white to light beige. The shell lacks distinct color banding, appearing naturally calcified. It shows slight sun-bleaching. Interior (though not visible) is usually white, sometimes with a faint yellow hue.
Rarity
Common; frequently found on beaches across the Caribbean and Florida, especially after storms which churn up the sand.
Habitat
Shallow marine waters, typically found in sandy substrates, seagrass beds (Thalassia), and near coral reefs. They range from the intertidal zone down to roughly 100 feet deep.
Geographic Range
Western Atlantic: Florida, the Bahamas, and the West Indies to Brazil; also found in Bermuda.
Description
A robust, thick-walled bivalve characterized by its distinctively inflated, bulbous shape. The exterior is adorned with strong, sharp, concentric ridges that are closely spaced. A prominent, deep groove (the posterior sulcus) runs from the beak (umbo) to the rear margin, creating a characteristic 'indented' look. The texture is rough and calcified, designed for life buried in the sand.
Key Features
The most diagnostic feature is the deep fold or indented groove on the posterior side and the very high, curved beak (umbo) that leans forward. The concentric ridges are much stronger than any radial markings.
Collector Value
Low to modest ($1-$5). It is a staple of 'beginner' beachcomber collections due to its commonality and attractive, symmetrical shape. Deeply ridged, pristine specimens with both valves attached are more desirable.
Condition Notes
Good condition. The shell is whole with well-preserved concentric sculpture. The margins appear slightly worn (eroded) from surf action, and there is no remaining periostracum (organic skin), which is typical for beach-collected specimens.
Interesting Facts
Members of the Lucinidae family have a fascinating symbiotic relationship with sulfur-oxidizing bacteria living in their gills. These bacteria provide the clam with nutrients, allowing them to thrive in environments with low oxygen and high hydrogen sulfide, such as seagrass roots.
Ecological Role
They are infaunal filter feeders that play a critical role in nutrient cycling within seagrass ecosystems. Their presence can help detoxify sediments for the seagrass by removing sulfides through their bacterial symbionts.
Similar Species
Codakia orbicularis (Great White Lucine), which is larger and flatter with more crossing radial lines; and Phacoides pectinatus (Thick Lucine), which has less pronounced folding.
Beach Finding Tips
Look along the high-tide line (the wrack line) after a strong onshore wind. They are often found mixed in with shell hash on Caribbean sandy beaches. Because they are heavy, they tend to settle in pockets of thicker sand.