Scotch Bonnet (Alternate names: Banded Tun, Bonnet Shell)
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Cassidae, Genus: Semicassis, Species: Semicassis granulata · Cassidae (Helmet and Bonnet family) · Gastropod, whole shell, oval-globular spiral shape
Species
Semicassis granulata
Shell Type
Gastropod, whole shell, oval-globular spiral shape
Family
Cassidae (Helmet and Bonnet family)
Size
Approximately 3 to 3.5 inches in length, which is average to large for this species. Adults typically range from 2 to 4 inches.
Color & Pattern
Creamy-white or pale yellowish base color, adorned with distinct rows of square or rectangular reddish-brown spots and blotches forming spiral bands. The surface features fine granular texture and spiral cords.
Rarity
Common to Uncommon, frequently found by dedicated beachcombers after storms or dredged by commercial shrimpers.
Habitat
Found in shallow subtidal to moderately deep waters, typically dwelling on sandy bottoms, offshore sandbars, and near seagrass beds.
Geographic Range
Western Atlantic Ocean, ranging from North Carolina through the Gulf of Mexico, the Caribbean Sea, and down to Brazil.
Description
An attractive and classic marine gastropod featuring a rounded, inflated body whorl, a short spire, and a distinctively patterned exterior with rows of warm brown squares against a pale background. The outer lip is thickened and slightly toothed inside.
Key Features
Inflated rounded body whorl, low spire, finely beaded or granulated spiral cords, and characteristic rows of brown square markings.
Collector Value
Moderately high collectibility, especially popular among regional Atlantic and Caribbean shell collectors. Typical specimens hold a modest commercial value of 5 to 20 dollars depending on size and grade.
Condition Notes
The specimen appears to be in good to fine condition with intact color patterns and a solid structure, showing minimal wear on the spire and outer lip.
Interesting Facts
Scotch Bonnets are specialized predators that feed almost exclusively on sea urchins and sand dollars, using their acidic secretions and radula to bore through the test.
Ecological Role
Acts as a key carnivorous predator in sandy bottom marine ecosystems, helping to regulate sea urchin populations and maintaining benthic balance.
Similar Species
Can be confused with the Yellow Helmet (Cypraecassis testiculus) or other related bonnet shells, but distinguished by its finer granulation and specific square color patterning.
Beach Finding Tips
Best found by beachcombing on barrier island beaches following heavy offshore winds or winter storms, particularly along the coasts of North Carolina and Florida.