As small ovals, less than two inches long, with a characteristic shelf inside, it is obvious to see why these univalves are commonly called Slipper Shells or Boat Shells. This white or tan shell has irregular brown stripes or blotches on it and is one of very few univalves that do not form a coiled or spiral shaped shell. The shelf, which covers 1/3 to 1/2 of the aperture, supports and protects the snail inside. It attaches to hard objects with a large foot and remains still most of the time, sometimes attaching to rocks, Horseshoe Crabs, and other shells such as oysters or even other Slippersnails. Slippersnails can grow on top of oyster beds in such numbers that they may crowd out the oysters. These univalves filter plankton like bivalves do and are hermaphroditic, containing both sex organs but operating them at different times during the spawning season or life to prevent self-fertilization. In general, younger more active snails are males with females being the larger individuals.