Slipper Snail (Common Slipper Shell, Boat Shell, Quarterdeck)
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Calyptraeidae, Genus: Crepidula, Species: C. fornicata · Calyptraeidae (Slipper snail family) · Gastropod (Univalve); Oval/Slipper-shaped with an internal shelf.
Species
Crepidula fornicata
Shell Type
Gastropod (Univalve); Oval/Slipper-shaped with an internal shelf.
Family
Calyptraeidae (Slipper snail family)
Size
Approximately 1 inch (2.5 cm). Adults typically range from 0.75 to 2 inches (2-5 cm).
Color & Pattern
Mottled brown and tan exterior with wavy darker brown streaks and spots. The interior is polished white to light tan, featuring a white horizontal shelf (septum) that covers about half the aperture.
Rarity
Very Common
Habitat
Marine; found in intertidal and shallow subtidal zones. They often stack on top of one another or attach to other shells, rocks, and horseshoe crabs.
Geographic Range
Native to the Western Atlantic from Canada to the Gulf of Mexico; highly invasive in Europe and the Pacific.
Description
An oval, slightly convex gastropod shell lacking a visible external spire. The exterior is relatively smooth but shows fine growth lines. Its most distinctive feature is the internal 'deck' or shelf, which gives it the appearance of a tiny boat or slipper.
Key Features
The internal horizontal shelf (septum) that covers half of the opening; the lack of a coiled spire; the frequent occurrence of 'stacks' where multiple individuals live piled together.
Collector Value
Minimal monetary value due to extreme abundance. They are primarily valued for educational purposes or as 'curiosity' shells for beginning collectors.
Condition Notes
The specimen appears to be a beach-worn whole shell. The outer edges of the aperture are slightly chipped, and the color is somewhat dull due to sand abrasion. Overall collectibility grade: Good (for a common beach find).
Interesting Facts
Slipper snails are sequential hermaphrodites; they begin life as males and turn into females as they grow larger. In a stack, the large ones at the bottom are female and the smaller ones on top are male.
Ecological Role
Suspension feeders that filter plankton from the water. They provide substrate for other organisms but can become pests in oyster beds by competing for food and space.
Similar Species
Crepidula convexa (Convex Slipper Shell) which is smaller and more inflated, and Crepidula plana (Eastern White Slipper Shell) which is flat and pure white.
Beach Finding Tips
Look in the drift line at Holden Beach after high tide. They are often found attached to large Atlantic surf clam shells or whelk shells. Look for the 'stacks' of shells fused together.
Notes
Holden Beach, NC