Passage 6.20.17
λέγουσι δὲ καὶ ὡς Μυρτίλῳ κενὸν ἐνταῦθα ἠρίον ποιήσειε Πέλοψ καὶ θύσειέ τε αὐτῷ τὸ ἐπὶ τῷ φόνῳ μήνιμα ἰώμενος καὶ ἐπονομάσαι Ταράξιππον, ὅτι τῷ Οἰνομάῳ διὰ τοῦ Μυρτίλου τῆς τέχνης ἐταράχθησαν αἱ ἵπποι· τοῖς δέ ἐστιν εἰρημένον ὡς αὐτὸς Οἰνόμαος ὁ τοὺς ἱππεύοντάς ἐστιν ἐν τῷ δρόμῳ βλάπτων. ἤκουσα δὲ καὶ ἐς τὸν Πορθάονος Ἀλκάθουν ἀγόντων τὴν αἰτίαν, ὡς ἐνταῦθα μέρη λάβοι γῆς ὁ Ἀλκάθους ἀποθανὼν ὑπὸ Οἰνομάου τῶν Ἱπποδαμείας γάμων ἕνεκα· ἅτε δὲ ἀτυχήσαντα ἐν ἱπποδρόμῳ, βάσκανόν τε εἶναι τοῖς ἱππεύουσι καὶ οὐκ εὐμενῆ δαίμονα.
They also say that Pelops here created an empty tomb for Myrtilus, sacrificed to him to soothe the wrath caused by the murder, and named him Taraxippus ("Horse-terrifier"), because Oenomaus's horses were thrown into confusion by means of Myrtilus's trickery. Some, however, maintain that it is Oenomaus himself who harms the charioteers in the racecourse. I have also heard that Alcathous, son of Porthaon, is responsible, inasmuch as Alcathous, having been slain here by Oenomaus because of Hippodameia's marriage, was given a portion of earth; since he had suffered misfortune in the racecourse, he became a spiteful and unfriendly spirit hostile toward charioteers.