Passage 8.14.11
Ἱπποδαμείας δὲ ἤρα μὲν καὶ αὐτὸς ὁ Μυρτίλος, ἐς δὲ τὸν ἀγῶνα ἀτόλμως ἔχων ὑπεῖκε καὶ ἡνιόχει τῷ Οἰνομάῳ. τέλος δὲ καὶ ἀναφανῆναι τοῦ Οἰνομάου προδότην φασὶν αὐτὸν ὑπαχθέντα ὅρκοις, ὥς οἱ νύκτα ὁ Πέλοψ μίαν Ἱπποδαμείᾳ συγγενέσθαι παρήσει. ἀναμιμνήσκοντα οὖν τῶν ὅρκων ὁ Πέλοψ ἐξέβαλεν ἐκ τῆς νεώς· Φενεᾶται δὲ τοῦ Μυρτίλου τὸν νεκρὸν ἐκβληθέντα ὑπὸ τοῦ κλύδωνος λέγουσιν ἀνελόμενοι θάψαι, καὶ νύκτωρ κατὰ ἔτος ἐναγίζουσιν αὐτῷ.
Myrtilus himself was in love with Hippodameia, yet feeling hesitant about entering the contest, he yielded and served as charioteer to Oenomaus. Ultimately, they say, he was persuaded by vows to betray Oenomaus, for Pelops pledged to allow him to lie with Hippodameia for one night. However, reminding Pelops thereafter of the promised oath, he was cast from the ship by him. The Pheneatians say his body, after being washed ashore by the waves, was recovered and buried by them; and every year they offer nocturnal sacrifices to his spirit.