Checkered Bonnet (alternate names: Western Bonnet, Scotch Bonnet variant)
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Cassidae, Genus: Semicassis, Species: centiquadrata · Cassidae (Bonnet and Helmet shell family) · Gastropod (univalve snail), whole shell, spiral/globose shape.
Species
Semicassis centiquadrata (Confidence: 90%)
Shell Type
Gastropod (univalve snail), whole shell, spiral/globose shape.
Family
Cassidae (Bonnet and Helmet shell family)
Size
Approximately 1.5-2.5 inches. This specimen appears to be sub-adult; typical adult size ranges from 2 to 4 inches.
Color & Pattern
Base color is a creamy white to pale tan, overlaid with distinct rows of rectangular brown or orangish-brown spots forming a checkered or 'squarish' grid pattern. The spiral bands of color are separated by white interstitial spaces. Typical of the Cabo/Panamic region, these markings are usually crisp and vibrant unless sun-bleached.
Rarity
Uncommon to Common. While widely distributed in the Panamic province, high-quality specimens are more frequently found by divers or after heavy storms than through casual beachcombing.
Habitat
Found in subtidal environments, typically on sandy bottoms at depths ranging from 10 to 100 meters. They often bury themselves in the sand during the day.
Geographic Range
Eastern Pacific region, specifically from the Gulf of California (Cabo San Lucas) south to Peru and the Galapagos Islands.
Description
A lightweight but sturdy globose shell characterized by a large body whorl and a relatively short spire. The surface is sculpted with numerous spiral grooves that intersect with the color pattern to emphasize the 'checkered' look. The aperture is large and oval, with a thickened outer lip (varix) that often features small teeth-like projections (denticles) in mature specimens. The columella typically has a distinct pucker or granules near the base.
Key Features
Checkered pattern of rectangular spots, globose shape, thin but strong shell walls, and the specific spiral ribbing that defines the spots into a grid.
Collector Value
Modest collector value ($5–$25 USD depending on size and lip quality). It is a desirable representative of the Panamic fauna and is popular due to its attractive geometric pattern.
Condition Notes
The image shows a specimen with well-preserved color and pattern, suggesting it was not exposed to the sun for an extended period. The apex appears intact. Collectibility grade: Fine to Good. A 'Gem' grade would require a perfectly thickened, gleaming outer lip and no chips on the canal.
Interesting Facts
Members of the Cassidae family are specialized predators that feed almost exclusively on sea urchins. They use a combination of acidic secretions and a specialized radula to drill through the urchin's calcium carbonate tests (shells).
Ecological Role
A secondary consumer that helps regulate sea urchin populations. They are vital to the health of sandy-bottom ecosystems by preventing overgrazing of seagrasses by urchins.
Similar Species
Semicassis granulata (Scotch Bonnet) from the Atlantic, which has more pronounced beaded sculpture; and Phalium bandatum, which has different banding and a smoother texture.
Beach Finding Tips
In the Cabo region, look for these after summer storms or high tides on sandy beaches near deep drop-offs. Search the 'wrack line' where debris accumulates, as their light weight allows them to be pushed further up the shore.
Notes
Cabo