Crepidula fornicata
This gastropod is easy to identify as the shell has a shelf on its interior, making it resemble a bedroom slipper. It can be smooth or wrinkled and grow to 1 1/2 inches.
The Atlantic Slipper feeds by filtering out food brought into the mantle cavity by water currents. There, the food is covered by a mucous secretion and drawn into the stomach. It spends its entire life in one spot attached to a hard surface. This means that an opercula (door) or another half shell is not required.
The snail is often attached to other slippers, making reproduction convenient. They are hermaphroditic (a single individual alternates sexes) and lay 70 to 100 eggs in thin-walled capsules. The Atlantic Slipper has few predators and can become quite numerous. This can be a threat to Oysters, as they compete to filter from the same food source.
Live shells should never be taken from any Florida State Park.