Slipper Limpet, Slipper Snail, Boat Shell
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Calyptraeidae, Genus: Crepidula, Species: Crepidula aculeata · Calyptraeidae (Slipper Snail or Cup-and-saucer family) · Gastropod (Univalve); Cap-shaped/Limpet-like shell with an internal shelf.
Species
Crepidula cf. aculeata (Prickly Slipper Snail)
Shell Type
Gastropod (Univalve); Cap-shaped/Limpet-like shell with an internal shelf.
Family
Calyptraeidae (Slipper Snail or Cup-and-saucer family)
Size
Approximately 20-30mm in length. This is standard for the species, which typically ranges from 10mm to 40mm.
Color & Pattern
Dull brownish-grey to olive exterior. The surface appears heavily weathered and encrusted with marine growth or mineral deposits. The natural cream or white interior shelf is likely obscured by sediment or erosion.
Rarity
Very Common
Habitat
Intertidal and shallow subtidal zones. They are sessile (attached) organisms found on rocks, other shells, or debris in sandy/muddy bays like Moreton Bay.
Geographic Range
Globally distributed in warm temperate to tropical waters; specifically common along the Queensland coast and Brisbane's Moreton Bay area.
Description
This is a heavily eroded specimen of a slipper snail. In life, these shells feature a distinctive internal horizontal shelf (the 'deck') that covers about half the aperture, giving it the appearance of a tiny boat or slipper. This specific specimen is significantly worn by wave action, obscuring the typically prickly or tiered sculpture of the shell's exterior.
Key Features
Ovate, asymmetrical cap shape; apex turned to one side; presence of an internal septum (shelf) on the underside (though not visible in this dorsal view); flattened base.
Collector Value
Minimal. These are extremely common and this specimen lacks the 'Gem' quality features like intact spines or vibrant interior luster.
Condition Notes
Poor to Fair. The shell is heavily beach-worn (tumbled), with significant loss of surface detail and possible calcification. It is an 'old' shell that has spent considerable time in the surf zone.
Interesting Facts
Slipper snails are sequential hermaphrodites; they often live in stacks where the larger individual at the bottom is female and the smaller ones on top are male. If the female dies, the largest male will change sex to replace her.
Ecological Role
Filter feeders that clean the water column by trapping plankton and detritus in mucus on their gills. They serve as a food source for predatory snails and crabs.
Similar Species
Crepidula convexa (usually smaller/smoother) or various species of true Limpets (which lack the internal shelf).
Beach Finding Tips
Look along the high-tide line at Brighton Beach/Sandgate after a storm. They are often found still attached to the shells of larger dead mollusks or hermit crab homes.
Notes
Brighton beach Sandgate in Brisbane