Passage 2.34.4
τὰ μὲν δὴ Μέθανα ἰσθμός ἐστι τῆς Πελοποννήσου· ἐντὸς δὲ τοῦ ἰσθμοῦ τῆς Τροιζηνίων ὅμορός ἐστιν Ἑρμιόνη. οἰκιστὴν δὲ τῆς ἀρχαίας πόλεως Ἑρμιονεῖς γενέσθαι φασὶν Ἑρμίονα Εὔρωπος. τὸν δὲ Εὔρωπα ---ἦν γὰρ δὴ Φορωνέως---Ἡροφάνης ὁ Τροιζήνιος ἔφασκεν εἶναι νόθον· οὐ γὰρ δή ποτε ἐς Ἄργον τὸν Νιόβης θυγατριδοῦν ὄντα Φορωνέως τὴν ἐν Ἄργει περιελθεῖν ἂν ἀρχὴν παρόντος Φορωνεῖ γνησίου παιδός.
Methana is indeed an isthmus of the Peloponnesus. Within this isthmus, Hermione borders upon the territory of Troezen. The people of Hermione say that their ancient city was founded by Hermion, son of Europs. Now, Herophanes of Troezen stated that Europs—who was a son of Phoroneus—was illegitimate; for it was never likely, he said, that Argus, the grandson of Niobe and descendant of Phoroneus, would have come to rule in Argos, had there been a legitimate son of Phoroneus still alive.