Apollodorus Library 2.5.10

[10]
  As a tenth labour he was ordered to fetch the kine of Geryon from Erythia. ¹ Now Erythia was an island near the ocean; it is now called Gadira. ² This island was inhabited by Geryon, son of Chrysaor by Callirrhoe, daughter of Ocean. He had the body of three men grown together and joined in one at the waist, but parted in three from the flanks and thighs. ³ He owned red kine, of which Eurytion was the herdsman and Orthus, ⁴ the two-headed hound, begotten by Typhon on Echidna, was the watchdog. So journeying through Europe to fetch the kine of Geryon he destroyed many wild beasts and set foot in Libya, ⁵ and proceeding to Tartessus he erected as tokens of his journey two pillars over against each other at the boundaries of Europe and Libya. ⁶ But being heated by the Sun on his journey, he bent his bow at the god, who in admiration of his hardihood, gave him a golden goblet in which he crossed the ocean. ⁷ And having reached Erythia he lodged on Mount Abas. However the dog, perceiving him, rushed at him; but he smote it with his club, and when the herdsman Eurytion came to the help of the dog, Hercules killed him also. But Menoetes, who was there pasturing the kine of Hades, reported to Geryon what had occurred, and he, coming up with Hercules beside the river Anthemus, ⁸ as he was driving away the kine, joined battle with him and was shot dead. And Hercules, embarking the kine in the goblet and sailing across to Tartessus, gave back the goblet to the Sun.
  And passing through Abderia ⁹ he came to Liguria, ¹⁰ where Ialebion and Dercynus, sons of Poseidon, attempted to rob him of the kine, but he killed them ¹¹ and went on his way through Tyrrhenia. But at Rhegium a bull broke away ¹² and hastily plunging into the sea swam across to Sicily, and having passed through the neighboring country since called Italy after it, for the Tyrrhenians called the bull italus, ¹³ came to the plain of Eryx, who reigned over the Elymi. ¹⁴ Now Eryx was a son of Poseidon, and he mingled the bull with his own herds. So Hercules entrusted the kine to Hephaestus and hurried away in search of the bull. He found it in the herds of Eryx, and when the king refused to surrender it unless Hercules should beat him in a wrestling bout, Hercules beat him thrice, killed him in the wrestling, and taking the bull drove it with the rest of the herd to the Ionian Sea. But when he came to the creeks of the sea, Hera afflicted the cows with a gadfly, and they dispersed among the skirts of the mountains of Thrace. Hercules went in pursuit, and having caught some, drove them to the Hellespont; but the remainder were thenceforth wild. ¹⁵ Having with difficulty collected the cows, Hercules blamed the river Strymon, and whereas it had been navigable before, he made it unnavigable by filling it with rocks; and he conveyed the kine and gave them to Eurystheus, who sacrificed them to Hera.