Frog Shell (Giant Frog Shell or Common Frog Shell)
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Bursidae, Genus: Bursa, Species: Bursa bufo · Bursidae (Frog Shell family) · Gastropod, whole shell, spiral and nodulose shape
Species
Bursa bufo
Shell Type
Gastropod, whole shell, spiral and nodulose shape
Family
Bursidae (Frog Shell family)
Size
Approximately 2 to 3 inches visible length, which falls within the typical adult size range for this species (usually 2 to 4 inches).
Color & Pattern
Predominantly creamy white to pale beige overall, with brownish highlights concentrated near the apex and spire whorls. The colors appear slightly sun-bleached from exposure, typical of beach-collected specimens, showing dull matte textures rather than live-collected gloss.
Rarity
Common to Uncommon, frequently encountered by dedicated beachcombers and divers within its natural Indo-Pacific range.
Habitat
Inhabits shallow subtidal waters down to moderate depths, typically found on hard substrates, coral rubble, and sandy-rocky bottoms in tropical and subtropical marine environments.
Geographic Range
Indo-Pacific region, including tropical waters from East Africa through Southeast Asia, Indonesia, and northern Australia.
Description
A sturdy, heavy marine snail shell characterized by a robust, low-spired profile with prominent varices aligned on opposite sides of the whorls. It features strong spiral cords and rounded, bumpy nodules that give it a rough, wart-like texture reminiscent of toad skin, leading to its common name.
Key Features
Prominent alternating varices aligned nearly continuously up the spire, heavily nodulose surface sculpture, a deeply notched posterior siphonal canal, and a thick outer lip.
Collector Value
Low to moderate commercial value, highly accessible for beginner and intermediate shell collectors, typically valued between $2 to $10 depending on exact condition and size.
Condition Notes
Good condition for a beach-worn specimen. The overall structure is intact with minor surface wear, slight bleaching of the exterior coloration, and some trapped sand within the interstices.
Interesting Facts
Frog shells are carnivorous predators that feed primarily on marine worms and other benthic invertebrates. They possess a specialized proboscis and are well-camouflaged among coral rubble and rocks.
Ecological Role
Functions as a mid-level carnivorous predator in benthic marine food webs, helping control populations of small invertebrates and contributing calcium back to the marine substrate upon death.
Similar Species
Bursa rana (Frog Shell) and other members of the Bursidae family; distinguished by the specific arrangement of varices, nodule spacing, and the shape of the anal canal.
Beach Finding Tips
Look along tropical Indo-Pacific high-tide drift lines, coral rubble zones, and shell grit beds after storms or strong onshore winds.