Common Slipper Shell, Boat Shell, Quarterdeck
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 an internal deck or shelf.
Species
Crepidula fornicata
Shell Type
Gastropod (univalve); Cap-shaped/Oval with an internal deck or shelf.
Family
Calyptraeidae (Slipper or Cup-and-saucer shells)
Size
Approximately 1 to 1.5 inches. This is standard for adults of the species, which typically peak around 2 inches.
Color & Pattern
Pale cream to tan base with brownish mottling and streaks. The exterior appears slightly weathered with soft orange-brown highlights at the apex. The interior (unseen) would typically be white to brown with a white horizontal shelf.
Rarity
Very Common; ubiquitous on beaches along the North Carolina coast like Holden Beach.
Habitat
Shallow marine waters, intertidal zones to 70 feet deep. They prefer hard substrates like rocks, other shells, or boat hulls.
Geographic Range
Native to the Western Atlantic from Canada to the Gulf of Mexico. Highly invasive in Europe and parts of the Pacific.
Description
An oval, convex gastropod shell shaped like a slipper or a small boat. The apex is curved to one side and shifted to the rear. The exterior is relatively smooth aside from concentric growth lines. The defining characteristic is an internal horizontal platform (septum) that covers about half the aperture.
Key Features
The distinctive internal shelf ('deck') resembling a slipper's toe; the asymmetric, coiled apex; and the tendency for shells to be found in stacks or with evidence of being stacked.
Collector Value
Low monetary value ($0.25 - $1.00) due to extreme abundance. Primarily used for educational purposes or as a 'starter' shell for children. High value for craft use in bulk.
Condition Notes
Good beach-found condition. The shell shows some surf-wear and minor erosion on the growth lines, and the color is slightly sun-bleached compared to a live specimen. Collectibility grade: Fair/Good.
Interesting Facts
These mollusks are sequential hermaphrodites; they start life as males and become females as they grow. They often live in stacks where the large females are at the bottom and smaller males are at the top.
Ecological Role
Suspension feeders that filter plankton from the water. They can be pests in commercial oyster beds as they compete for food and space. Not protected.
Similar Species
Crepidula plana (Eastern White Slipper Shell) which is flatter and pure white, and Crepidula convexa (Convex Slipper Shell) which is much smaller and more domed.
Beach Finding Tips
Look in the 'shell hash' lines at low tide. They are often found attached to the inside of dead horseshoe crab molts or discarded whelk shells.
Notes
Holden Beach, NC