"Common Slippersnail" or "Common Atlantic Slippersnail"
Crepidula fornicata (Linnaeus, 1758)
Family Calyptraeidae
The "Common Slippersnail" or "Common Atlantic Slippersnail" is easily found on S. Hutchinson Beaches They are arched with a inside deck or shelf where part of the snail resides. The shell length averages about an inch but large versions may reach almost 2".
The natural color is white or yellow/tan but shells have a variety of other colors (reds, dark yellows, black or gray) sometimes with stripe.