Atlantic Slippercell, Common Slipper Shell, Boat Shell
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Calyptraeidae, Genus: Crepidula, Species: Crepidula fornicata · Calyptraeidae (Slipper snail family) · Gastropod (univalve), whole shell, cap-shaped or slipper-shaped form
Species
Crepidula fornicata
Shell Type
Gastropod (univalve), whole shell, cap-shaped or slipper-shaped form
Family
Calyptraeidae (Slipper snail family)
Size
Approximately 1.5 inches in length. Adults typically range from 1 to 2 inches, making this specimen a standard, average-sized adult.
Color & Pattern
Off-white to pale cream base coloration with faint, weathered brownish markings near the apex. The colors are heavily sun-bleached due to environmental exposure. The interior exhibits a matching porcelain-white finish with a glossy internal shelf.
Rarity
Very Common
Habitat
Found in shallow subtidal and intertidal zones attached to hard substrates, rocks, other shells, or submerged structures. Typically marine, preferring quiet bays, estuaries, and coastal waters.
Geographic Range
Native to the Western Atlantic from Canada to the Gulf of Mexico and the Caribbean. Also introduced and well-established as an invasive species in European waters.
Description
A classic slipper shell exhibiting an oval, convex cap-like morphology resembling a tiny canoe or slipper. The apex is curved and off-center. A prominent, white internal shelf (the deck) covers the posterior half of the aperture, serving as an attachment point for the animal's strong retractor muscle.
Key Features
Cap-shaped or boat-like univalve shell with a distinctive internal horizontal platform (septum) extending across the posterior half of the aperture.
Collector Value
Low to moderate value. While extremely common and inexpensive, they are staple educational and beginner collection pieces due to their unique stacking behavior and internal deck structure.
Condition Notes
Good overall condition with minor wear and small bore holes near the apex, typical of beach-worn specimens. Collectibility grade is Good.
Interesting Facts
Crepidula fornicata are protandrous hermaphrodites, meaning they start life as males and later transform into females. They stack on top of one another in chains, where larger females sit at the bottom and smaller males remain on top.
Ecological Role
Suspension feeders that filter phytoplankton from the water column. They can form dense aggregations that alter benthic habitats, and they are sometimes considered pests in commercial oyster beds.
Similar Species
Crepidula plana (Eastern White Slipper Shell), which is much flatter and lives inside the apertures of other gastropod shells, and Crepidula convexa (Convex Slipper Shell), which is smaller and more domed.
Beach Finding Tips
Look along drift lines on sandy and shelly beaches, or check empty larger gastropod shells where slipper shells frequently attach.