Common Slippershell, Boat Shell, Quarterdeck
Phylum: Mollusca, Class: Gastropoda, Order: Littorinimorpha, Family: Calyptraeidae, Genus: Crepidula, Species: C. fornicata · Calyptraeidae (Slipper snail or Cup-and-saucer family) · 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 snail or Cup-and-saucer family)
Size
Approximately 1.5 cm (0.6 inches). This is a juvenile or smaller specimen, as adults typically reach 2.5 to 5 cm.
Color & Pattern
Uniformly creamy white to off-white. In this specimen, it appears sun-bleached or naturally calcified white, lacking the typical brown mottled streaks or tan 'fingerprint' patterns seen in live or fresh shells.
Rarity
Very Common. These are among the most frequently found shells on Atlantic and Caribbean beaches.
Habitat
Found in intertidal and shallow subtidal zones, typically in bays and estuaries. It attaches to hard substrates including rocks, other shells, and boat hulls.
Geographic Range
Western Atlantic from Canada to the Gulf of Mexico and Caribbean (including Cancun). It has also become an invasive species in Europe and the Pacific.
Description
An oval, convex gastropod shell shaped like a slipper or a small boat. The interior features a distinct, flat calcareous plate (the 'deck') that covers about half of the aperture, resembling a seat in a rowboat.
Key Features
The most diagnostic feature is the internal horizontal shelf or deck. The apex is turned to one side and situated at the posterior end, giving it a slightly asymmetrical, cap-like appearance.
Collector Value
Minimal monetary value due to extreme abundance. Its primary value is educational, illustrating the unique diversity of gastropod morphology.
Condition Notes
Fair to Good. The shell is beach-worn and sun-bleached, which has removed the natural brown pigment and smoothed the exterior sculpture. The internal deck appears mostly intact, which is the primary value for identification.
Interesting Facts
These snails are sequential hermaphrodites; they start life as males and turn into females as they age. They often live in 'stacks' where the large females are at the bottom and smaller males are on top.
Ecological Role
Filter feeders that clean the water column of plankton. While they are a food source for starfish and drills, they can be a nuisance in oyster beds as they compete for space and food.
Similar Species
Crepidula convexa (Convex Slipper) which is much smaller and more deeply curved, or Crepidula plana (Eastern White Slipper) which is much flatter.
Beach Finding Tips
Look in the 'wrack line' (debris left by high tide) or among clusters of larger shells like whelks as they often wash up attached to other objects.
Notes
Cancun