Common Slipper Shell, Boat Shell, Quarterdeck Shell
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Calyptraeidae, Genus: Crepidula, Species: C. fornicata · Calyptraeidae (Slipper or Cup-and-saucer shells) · Gastropod (univalve); Cap-shaped/Oval with internal deck. Visible as a whole shell.
Species
Crepidula fornicata
Shell Type
Gastropod (univalve); Cap-shaped/Oval with internal deck. Visible as a whole shell.
Family
Calyptraeidae (Slipper or Cup-and-saucer shells)
Size
Approximately 1 inch (25mm) in length. This is an average juvenile/young adult size for this species, which typically reaches 1-2.5 inches.
Color & Pattern
Dull white to grayish-white base with prominent reddish-brown flecks and wavy streaks. The pattern is somewhat eroded. Interior typically features a white shelf or 'deck'.
Rarity
Very Common. One of the most frequently found shells by beachcombers on the US Atlantic coast.
Habitat
Intertidal and shallow subtidal zones. Attaches to rocks, other shells, or hard substrates in marine environments. Often found in estuaries and coastal lagoons.
Geographic Range
Western Atlantic from Canada to the Gulf of Mexico. Very common on the coast of South Carolina including Myrtle Beach.
Description
An oval, arched shell lacking a visible external spire. The exterior has a slightly rough texture with growth lines. Its most famous feature is the internal horizontal plate (shelf) that covers about half the aperture, resembling a slipper or a boat's deck.
Key Features
Oval dome shape, absence of spiral form, and the presence of a white internal 'deck' or septum that provides a secure area for the animal's muscle.
Collector Value
Low monetary value due to extreme abundance. Primarily used for educational purposes, craft projects, or as a representative species in a regional collection.
Condition Notes
Fair to Good condition. Shows some beach-wear and erosion on the apex. The color mottling is still visible, but the glossy finish of a live-taken shell has been buffed by sand and surf.
Interesting Facts
These mollusks are sequential hermaphrodites; they begin life as males and turn into females as they grow larger. They often live in 'stacks' where the largest at the bottom is female and the smaller ones on top are male.
Ecological Role
Filter feeders that help clear water of plankton and organic detritus. In some regions outside their native range, they are considered a nuisance invasive species that outcompetes local shellfish.
Similar Species
Crepidula convexa (Convex Slipper Shell) which is smaller and darker; Crepidula plana (Eastern White Slipper Shell) which is much flatter and pure white.
Beach Finding Tips
Look in the shell hash along the high tide line after a storm. They are often found attached to one another or to the shells of larger whelks and horseshoe crabs.
Notes
Myrtle Beach SC