The name `` Nautilus '' originally referred to the Argonauta , otherwise known as paper nautiluses , because they allegedly use their two expanded arms as sails ( cf . Aristotle Historia Animalium 622b ) . The name `` Nautilus '' originally referred to the Argonauta , otherwise known as paper nautiluses , because the ancients believed these animals used their two expanded arms as sails ( cf . Aristotle Historia Animalium 622b ) .