Atlantic Slipper Snail, Slipper Shell, Boat Shell, Quarterdeck
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Calyptraeidae, Genus: Crepidula, Species: C. fornicata · Calyptraeidae (Slipper snail or Cup-and-saucer snail family) · Gastropod (univalve); oval/slipper-shaped shell with an internal shelf (septum).
Species
Crepidula fornicata
Shell Type
Gastropod (univalve); oval/slipper-shaped shell with an internal shelf (septum).
Family
Calyptraeidae (Slipper snail or Cup-and-saucer snail family)
Size
Approximately 0.75 - 1 inch (19-25mm). Natural range for adults is 1 to 2 inches. This specimen is a mid-sized juvenile or small adult.
Color & Pattern
The shell displays a creamy white to tan base with distinct reddish-brown mottled streaks and wavy radiating lines. The interior shelf is a translucent white, and the inner cavity shows a polished, somewhat pearly tan or purplish-brown hue. Colors appear natural and well-preserved within the resin.
Rarity
Very Common. These are some of the most frequently found shells on Sanibel beaches, though finding a perfectly intact, colorful specimen for jewelry is preferred.
Habitat
Intertidal and shallow subtidal zones; typically found attached to rocks, other shells (especially horseshoe crabs and mussels), or stacked upon one another. Marine environment.
Geographic Range
Native to the Western Atlantic from Canada to the Gulf of Mexico; extremely abundant around Sanibel Island and the Florida Gulf Coast.
Description
An oval, convex gastropod shell that lacks a visible spiral. The most distinguishing feature is the internal flat platform or 'shelf' that covers about half the aperture, giving it the appearance of a tiny slipper or boat. The exterior is smooth but may show faint growth lines.
Key Features
Deck or septum (internal horizontal plate), apex turned to one side and slightly posterior, lack of a true operculum, and a cap-like shape.
Collector Value
Low monetary value due to extreme abundance, but high aesthetic value in jewelry. Individual shells are usually found in 'baskets' or 'bulk' assortments; as a finished jewelry piece, value is $15–$30.
Condition Notes
The shell appears to be in 'Fine' to 'Gem' condition. It is a 'dead-taken' beach shell that has been polished or cleaned before being encased in resin. The lip appears smooth and unbroken, and the pigmentation is vibrant.
Interesting Facts
These snails are sequential hermaphrodites; they live in stacks where the large ones at the bottom are female and the smaller ones on top are male. If the females at the bottom die, the males above them change sex to become female.
Ecological Role
Filter feeders that help clear particulate matter from the water column. They provide substrate for other encrusting organisms but can be an invasive nuisance in European oyster beds where they compete for food.
Similar Species
Crepidula convexa (Convex Slipper Shell) which is smaller and darker, and Crepidula plana (Eastern White Slipper Shell) which is much flatter and purely white.
Beach Finding Tips
Walk the drift lines after a high tide on Sanibel's Gulf side. Look for small, arched shapes nestled among shell hash. They often wash up still attached to large chunks of limestone or Atlantic Giant Cockle shells.
Notes
Sanibel