Scotch Bonnet, also known as the Banded Tun or Yellow Tun
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Tonnidae, Genus: Semicassis, Species: Semicassis granulata · Tonnidae (Tun family and helmet allies) · Gastropod, whole shell, spiral shape with rounded body whorl
Species
Semicassis granulata
Shell Type
Gastropod, whole shell, spiral shape with rounded body whorl
Family
Tonnidae (Tun family and helmet allies)
Size
Approximately 1.5 to 2 inches in length. Adults typically range from 1.5 to 3.5 inches.
Color & Pattern
Creamy white to light golden-brown base color featuring distinctive rows of square or rectangular reddish-brown spots along the spiral cords. The colors appear natural and well-preserved with typical warm tones.
Rarity
Common to Uncommon, frequently sought after by beachcombers in the southeastern United States and the Caribbean.
Habitat
Found in shallow subtidal waters to moderate depths, typically inhabiting sandy bottoms, offshore sand bars, and areas near coral reefs or rocky outcroppings in marine environments.
Geographic Range
Western Atlantic Ocean, ranging from North Carolina down through the Gulf of Mexico, the Caribbean, and south to Brazil.
Description
A sturdy, globular shell with a low spire and a very large body whorl. The surface is heavily sculpted with numerous flat, spiral cords intersected by fine vertical grooves, creating a beaded or granulated texture. The aperture is wide with a thickened, reflected outer lip showing subtle denticles inside.
Key Features
Globular shape, low spire, flattened spiral cords with beaded texture, and characteristic rows of square reddish-brown spots arranged in distinct bands.
Collector Value
Moderately valued by collectors. While common in certain regions, attractive specimens with clear banding patterns are popular additions to beginner and intermediate collections, generally valued between $5 to $20 depending on size and condition.
Condition Notes
Good condition, intact structure with slight natural wear on the spire. Colors are mostly retained with minor fading. Collectibility grade is Good to Fine.
Interesting Facts
Members of the Tonnidae family are known to feed primarily on sea urchins and other echinoderms by drilling or dissolving their tests with specialized acidic secretions.
Ecological Role
Acts as an important carnivorous predator in benthic marine ecosystems, helping to regulate sea urchin populations. Empty shells frequently serve as mobile homes for hermit crabs.
Similar Species
Can be confused with other helmet and tun shells such as Phalium species, but distinguished by its smaller size, granulated spiral cords, and specific square-spot color patterns.
Beach Finding Tips
Best found by beachcombing along sandy shores of the southeastern United States, particularly after strong offshore storms or rough wave action that stirs up offshore sandbars.