It was a simple nautical instrument used to orientate the navigation. It consisted of a disc with radiuses which indicated the direction of the twelve winds (Aparctias, Boreas, Caecias, Apeliotes, Eurus, Euronotos, Notos, Libonotos, Lips, Zephyrus, Argestes, Thrascias). It is most likely that the centre had a rotating vane (strip, statuette, Triton, etc.) and at its circumference it had twelve oblique pegs as on the later anemoscope of Eutropius.