Passage 4.33.3
ἰόντι δὲ τὴν ἐπʼ Ἀρκαδίας ἐς Μεγάλην πόλιν ἐστὶν ἐν ταῖς πύλαις Ἑρμῆς τέχνης τῆς Ἀττικῆς · Ἀθηναίων γὰρ τὸ σχῆμα τὸ τετράγωνόν ἐστιν ἐπὶ τοῖς Ἑρμαῖς, καὶ παρὰ τούτων μεμαθήκασιν οἱ ἄλλοι. σταδίους δὲ καταβάντι ἀπὸ τῶν πυλῶν τριάκοντα τὸ ῥεῦμά ἐστι τῆς Βαλύρας. γενέσθαι δὲ τὸ ὄνομα τῷ ποταμῷ λέγουσι Θαμύριδος τὴν λύραν ἐνταῦθα ἀποβαλόντος ἐπὶ τῇ πηρώσει· παῖδα δὲ αὐτὸν Φιλάμμωνος καὶ Ἀργιόπης τῆς νύμφης εἶναι. τὴν δὲ Ἀργιόπην τέως μὲν περὶ τὸν Παρνασσὸν οἰκεῖν, ἐπεὶ δὲ εἶχεν ἐν γαστρί, ἐς Ὀδρύσας λέγουσι μετοικῆσαι· Φιλάμμωνα γὰρ οὐκ ἐθέλειν ἐς τὸν οἶκον αὐτὴν ἄγεσθαι. καὶ Θάμυριν μὲν Ὀδρύσην τε καὶ Θρᾷκα ἐπὶ τούτῳ καλοῦσιν· ἡ δὲ Λευκασία καὶ Ἄμφιτος συμβάλλουσιν ἐς τὸ αὐτὸ τὰ ῥεύματα.
When you go towards Arcadia, at the gate into Megalopolis there is a statue of Hermes in the Attic style. For the Athenians represented their Herms with a square shape, and other peoples have learned this from them. Thirty stades below the gate flows the river Balyra. They say that the river received its name from Thamyris casting his lyre into it at the time of his blinding. Thamyris was said to be a son of Philammon and the nymph Argiope. This Argiope lived at first around Parnassus, but when she became pregnant, they say that she moved to the Odrysae, for Philammon did not wish to bring her into his house. For this reason Thamyris was called Odrysian and Thracian. The rivers Leukasia and Amphitos join their waters together.