Ampullariidae, common name the apple snails, is a family of large freshwater snails, aquatic gastropod mollusks with a gill and an operculum. This family is in the superfamily Ampullarioidea and is the type family of that superfamily. The Ampullariidae are unusual because they have both a gill and a lung, with the mantle cavity being divided in order to separate the two types of respiratory structures. This adaptation allows these snails to be amphibious.Pomacea bridgesii, common names the spike-topped apple snail or mystery snail, is a South American species of apple snail that is considered invasive. Federal law states that it is illegal for apple snails to be imported across state lines.