Frog Shell (specifically the Granular Frog Shell or Common Frog Shell)
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Bursidae, Genus: Bursa, Species: Bursa granularis · Bursidae (Frog Shell family) · Gastropod (snail/univalve); Spiral/Ovostromboid shape; Whole shell specimen.
Species
Bursa granularis (Confidence level: 85% based on nodule pattern and global distribution)
Shell Type
Gastropod (snail/univalve); Spiral/Ovostromboid shape; Whole shell specimen.
Family
Bursidae (Frog Shell family)
Size
Approximately 1.2 to 1.5 inches (30-38mm). This is on the smaller side for the genus, as adults can reach 2-3 inches, but it is a typical size for beach-worn specimens.
Color & Pattern
Creamy white to light beige base color. The specimen appears significantly 'beach-worn' or sun-bleached, which has faded the natural reddish-brown banding and spotting typically seen in live specimens. Fine spiral threads are visible between larger nodules.
Rarity
Common; frequently found washed up on tropical beaches, though finding a 'gem' quality specimen with a preserved lip and color requires more effort.
Habitat
Marine; typically found in shallow tropical waters, often under coral slabs, rocks, or in crevices within reefs. They range from the intertidal zone to depths of about 50 meters.
Geographic Range
Indo-Pacific and Western Atlantic regions. Highly cosmopolitan distribution across the Caribbean, Florida, and throughout the tropical Pacific from Hawaii to the Red Sea.
Description
An ovate, heavy-set shell characterized by its rugged, bumpy texture reminiscent of a frog's skin. It features two distinct rows of large, rounded nodules (varices) that coincide with growth stages. The surface is covered in fine, granular spiral cords. The spire is moderately high, though worn down in this specimen.
Key Features
The presence of two varices per whorl located at 180 degrees from each other, creating a flattened appearance when viewed from the top. Strong, blunt nodules on the body whorl and a distinct 'granular' surface texture.
Collector Value
Low collector value (approximately $1-$3 USD). While a staple for any beginner collection, the beach-worn condition and fading of this specific specimen make it more of a personal keepsake than a high-value investment piece.
Condition Notes
Fair condition. The specimen shows significant 'tumbled' wear from wave action, which has smoothed the finer details of the sculpture. The apex (tip) is eroded, and there are small pits indicating bio-erosion by sponges or acid. Not a gem-quality specimen, but a solid representative of the species shape.
Interesting Facts
Frog shells are closely related to Triton shells. They are predatory snails that hunt polychaete worms and other invertebrates. The name 'Bursa' is Latin for 'purse,' referring to the shape of the aperture in many species within this family.
Ecological Role
Active carnivore and scavenger. It plays a role in controlling worm populations within reef ecosystems. It is not currently protected or listed as endangered, though local reef collection laws may apply to live specimens.
Similar Species
Bursa bufonia (thicker, heavier) and Bursa rhodostoma (distinctive purple/rose tint to the aperture). Distinguishable from the Tutufa genus by its smaller size and flatter growth habit.
Beach Finding Tips
Look in tide pools and among coral rubble after a strong storm. They tend to lodge in crevices, so checking the 'line' of debris where shells accumulate behind reef structures is usually productive.