Passage 6.21.7
προϊόντι δὲ ἐντεῦθεν τό τε ὕδωρ τῆς Παρθενίας ἐστὶ καὶ πρὸς τῷ ποταμῷ τάφος ἵππων τῶν Μάρμακος· Ἱπποδαμείας δὲ μνηστῆρα ἔχει λόγος ἀφικέσθαι πρῶτον τοῦτον Μάρμακα καὶ ἀποθανεῖν ὑπὸ τοῦ Οἰνομάου πρὸ τῶν ἄλλων, ὀνόματα δὲ αὐτοῦ ταῖς ἵπποις Παρθενίαν τε εἶναι καὶ Ἐρίφαν---Οἰνόμαον δὲ ἐπικατασφάξαι μὲν τὰς ἵππους τῷ Μάρμακι, μεταδοῦναι μέντοι καὶ ταύταις ταφῆναι---, καὶ ὄνομα Παρθενίας τῷ ποταμῷ ἀπὸ ἵππου τῆς Μάρμακος.
Going forward from here is the water of Parthenia, and beside the river is the tomb of the horses of Marmakas. The tradition says that this Marmakas was the first of the suitors of Hippodameia to arrive, and that he was killed by Oinomaos before all the others. The names of his mares were Parthenia and Eripha; Oinomaos slaughtered Marmakas' horses as well, yet granted them burial. The Parthenia river received its name from this horse of Marmakas.