By far the most commonly accepted version of Draco's arrival in the heavens, however, is that Draco was the dragon killed by Cadmus. Cadmus was the brother of Europa, who was carried off to Crete by Jupiter in the form of a bull (Taurus).
It is interesting, however, to note that Ovid himself does not equate the dragon of Mars with Draco. In fact, in book III of Metamorphoses, he describes the dragon killed by Cadmus in terms of the constellation: "It was as huge as the Serpent that twines between the two Bears in the sky, if its full length were seen uncoiled".
The Serpent described by Ovid is certainly the same one as we see today, twisting past Cepheus and between Ursa Major and Ursa Minor in the north, with its head beneath the foot of Hercules.