White Baby's Ear, White Slipper Shell, or Lunule Slipper Snail
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Calyptraeidae, Genus: Crepidula, Species: Crepidula plana · Calyptraeidae (Slipper snails and cup-and-saucer shells) · Gastropod (univalve), whole shell, cap-shaped or slipper-shaped with a distinct internal deck.
Species
Crepidula plana
Shell Type
Gastropod (univalve), whole shell, cap-shaped or slipper-shaped with a distinct internal deck.
Family
Calyptraeidae (Slipper snails and cup-and-saucer shells)
Size
Approximately 1 inch (25 mm) in length, which is average for a mature specimen. Adults typically range from 0.75 to 1.5 inches.
Color & Pattern
Uniform glossy porcelain-white exterior and interior. Completely monochromatic with no banding or spots. The colors are natural and unmodified by sun-bleaching, retaining a smooth, pearlescent finish inside the aperture.
Rarity
Common. Frequently found washed ashore inside empty gastropod shells or attached to rocks.
Habitat
Found in shallow marine and estuarine waters, often attached to hard surfaces such as rocks, pier pilings, or more commonly, living inside or on the outer surfaces of the shells of other larger gastropods like whelks and conchs. Intertidal to shallow subtidal zones.
Geographic Range
Western Atlantic Ocean, ranging from Nova Scotia, Canada, down the coast of the United States, through the Gulf of Mexico, the Caribbean Sea, and south to Brazil.
Description
An attractive, smooth, flattened cap-shaped shell with an oval to slightly irregular outline matching the contour of its attachment substrate. The apex is small and marginal, often slightly hooked. The interior features a characteristic white, porcelain-like shelf or septum covering approximately the posterior half of the aperture, resembling a tiny deck or platform.
Key Features
Flattened, cap-like asymmetrical shape combined with the distinctive internal horizontal shelf (septum) covering the rear half of the aperture, and a completely pure white coloration.
Collector Value
Low to moderate commercial value, but a staple collection piece for general shell enthusiasts and educational displays. Usually valued at under a dollar individually, though pristine sets or interesting examples attached to host shells are prized by regional collectors.
Condition Notes
Gem to Fine condition. The shell is fully intact, retains its original glossy porcelain-white finish, has no chips along the delicate margin, and the internal deck is structurally sound with no fractures.
Interesting Facts
Like other slipper snails, Crepidula plana are sequential hermaphrodites, starting life as males and later transforming into females. They often stack on top of one another in living colonies, where the largest bottom individuals are female and the smaller top individuals are male.
Ecological Role
Acts as a suspension feeder, filtering microscopic plankton and organic particles from the water column. They serve as a food source for larger predatory gastropods, fish, and crabs, and play an integral role in benthic marine food webs.
Similar Species
Crepidula fornicata (Common Slipper Shell), which is much more arched, vaulted, and typically brownish with spots. Crepidula convexa, which is smaller and more convex.
Beach Finding Tips
Look inside empty washed-up whelk, conch, or moon snail shells along sandy or muddy beaches at low tide, as these little snails frequently inhabit the interior cavities of larger dead gastropods.