Passage 8.22.1
ἐπανάγει δὲ ὁ λόγος με ἐπὶ Στύμφαλον καὶ ἐπὶ τοὺς Φενεατῶν καὶ Στυμφαλίων ὅρους, τὸ ὀνομαζόμενον Γερόντειον. Στυμφάλιοι δὲ τεταγμένοι μὲν οὐ μετὰ Ἀρκάδων ἔτι εἰσὶν, ἀλλὰ ἐς τὸ Ἀργολικὸν συντελοῦσι μεταστάντες ἐς αὐτὸ ἐθελονταί· γένους δὲ εἶναι σφᾶς τοῦ Ἀρκάδων τὰ ἔπη μαρτυρεῖ τὰ Ὁμήρου, καὶ ὁ Στύμφαλος ὁ οἰκιστὴς ἀπόγονος ἦν τρίτος Ἀρκάδος τοῦ Καλλιστοῦς. λέγεται δὲ ἐξ ἀρχῆς ἑτέρωθι οἰκισθῆναι τῆς χώρας καὶ οὐκ ἐς τὴν ἐφʼ ἡμῶν πόλιν.
My narrative now brings me to Stymphalos and to the frontier between the Pheneatians and Stymphalians, to a place called Geronteion. The Stymphalians are no longer arranged among the Arcadians, but have willingly transferred themselves into Argolis and are counted part of that region. Nevertheless, their Arcadian origin is testified by the verses of Homer, and Stymphalos, their founder, was the third descendant from Arkas, the son of Callisto. It is said that in the beginning their city was founded elsewhere in the region, and not in the location of the present city.