Scotch Bonnet
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Cassidae, Genus: Semicassis, Species: Semicassis granulata (Bruguière, 1792) · Cassidae (Helmet and Bonnet shells) · Gastropod (Sea Snail); Globose/Spiral shell
Species
Semicassis granulata
Shell Type
Gastropod (Sea Snail); Globose/Spiral shell
Family
Cassidae (Helmet and Bonnet shells)
Size
Estimated 2 to 3 inches (5-7 cm). This is within the average adult size range of 1.5 to 4 inches.
Color & Pattern
Creamy white to light tan base with a characteristic pattern of square orange or yellowish-brown spots arranged in spiral rows. The specimen shown appears slightly sun-bleached, which is common for beach-found shells, softening the intensity of the spots.
Rarity
Common (found regularly on beaches, especially in the Southeast United States and Caribbean).
Habitat
Subtidal waters on sandy bottoms at depths ranging from 0 to 90 meters (up to 300 feet). They are marine gastropods often found in areas with high sand dollar populations.
Geographic Range
Western Atlantic, ranging from North Carolina south through the Gulf of Mexico, Caribbean, and down to Brazil.
Description
An elegant, globose shell featuring a short spire and a large body whorl. The surface is adorned with numerous spiral grooves (sulci) that create a textured, corded appearance. The outer lip is thickened and usually possesses small teeth-like ridges (variations depend on subspecies). Its shape and light weight make it a classic favorite for beachcombers.
Key Features
Distinguished by its distinct square-shaped brown spots, short spire, fine spiral ribbing, and a thickened, reflected outer lip. The aperture is large and contains a glazed columellar shield.
Collector Value
Low to Moderate ($3 - $10 USD). While common, high-quality, 'Gem' condition specimens with deep orange squares and intact lips are sought after by regional collectors. It is a staple of shell shops across the Atlantic coast.
Condition Notes
Good condition. The shell appears intact with no major breaks or chips visible in the spire. Some erosion and sun-fading on the pattern suggest it has been on the beach for some time. The 'Gem' grade is unlikely due to the faded color, but it remains a great specimen for a general collection.
Interesting Facts
The Scotch Bonnet was the first seashell to be named a state shell in the United States (North Carolina, 1965). The living animal is an active predator that specializes in eating sea urchins and sand dollars. The common name comes from the shell's resemblance to the traditional Scottish tam-o'-shanter cap.
Ecological Role
Active predator in the benthic community. By preying on sand dollars and sea urchins, they help regulate the populations of these echinoderms. They are also prey for larger crabs and octopuses.
Similar Species
The Mediterranean Bonnet (Semicassis saburon) is similar but lacks the distinct square spotting of S. granulata. Phalium bandatum is also similar but has more elongated spines on the shoulder.
Beach Finding Tips
Best found after storms or high winds along the Atlantic coast, particularly on the Outer Banks of North Carolina and the Gulf Coast of Florida. Look for them in the wrack line or at low tide on sandbars.