Passage 8.38.9
ταῦτα μὲν οὕτω ποιεῖν νομίζουσι, τοῦ Λυκαίου δὲ τὰ πρὸς τῆς ἄρκτου γῆ ἐστιν ἡ Θεισοαία· οἱ δὲ ἄνθρωποι μάλιστα οἱ ταύτῃ νύμφην τὴν Θεισόαν ἄγουσιν ἐν τιμῇ. διὰ δὲ τῆς χώρας τῆς Θεισοαίας ῥέοντες ἐμβάλλουσιν ἐς τὸν Ἀλφειὸν Μυλάων, ἐπὶ δὲ αὐτῷ Νοῦς καὶ Ἀχελῷος καὶ Κέλαδός τε καὶ Νάλιφος. Ἀχελῴω δὲ τῷ Ἀρκάδι εἰσὶν ἄλλοι δύο ὁμώνυμοί τε αὐτῷ ποταμοὶ καὶ τὰ ἐς δόξαν φανερώτεροι·
They hold these customs thus. North of Mount Lycaeus lies the territory of Theisoa, and the inhabitants there especially honor the nymph Theisoa. Through the country of Theisoa flows the river Mylaon, which empties into the Alpheius. Tributaries of Mylaon are the Nous, the Acheloüs, the Celadus and the Naliphus. Besides this Acheloüs in Arcadia, there are two other rivers of the same name, both better known and more frequently mentioned.