Passage 2.21.5
τοῦ δὲ ἐν τῇ ἀγορᾷ τῶν Ἀργείων οἰκοδομήματος οὐ μακρὰν χῶμα γῆς ἐστιν· ἐν δὲ αὐτῷ κεῖσθαι τὴν Μεδούσης λέγουσι τῆς Γοργόνος κεφαλήν. ἀπόντος δὲ τοῦ μύθου τάδε ἄλλα ἐς αὐτήν ἐστιν εἰρημένα· Φόρκου μὲν θυγατέρα εἶναι, τελευτήσαντος δέ οἱ τοῦ πατρὸς βασιλεύειν τῶν περὶ τὴν λίμνην τὴν Τριτωνίδα οἰκούντων καὶ ἐπὶ θήραν τε ἐξιέναι καὶ ἐς τὰς μάχας ἡγεῖσθαι τοῖς Λίβυσι καὶ δὴ καὶ τότε ἀντικαθημένην στρατῷ πρὸς τὴν Περσέως δύναμιν---ἕπεσθαι γὰρ καὶ τῷ Περσεῖ λογάδας ἐκ Πελοποννήσου--- δολοφονηθῆναι νύκτωρ, καὶ τὸν Περσέα τὸ κάλλος ἔτι καὶ ἐπὶ νεκρῷ θαυμάζοντα οὕτω τὴν κεφαλὴν ἀποτεμόντα αὐτῆς ἄγειν τοῖς Ἕλλησιν ἐς ἐπίδειξιν.
Not far from the building in the marketplace of the Argives, there is a mound of earth; they say that the head of the Gorgon Medusa lies within it. Apart from the mythical tradition, this other version about her is also recorded: that she was a daughter of Phorcus, and upon her father's death she succeeded him as ruler of the people who dwell around Lake Tritonis; that she habitually went out hunting and led the Libyans into battle, and at that time indeed opposed her army to the force commanded by Perseus—for Perseus, too, was attended by chosen fighters from the Peloponnese. It is said she was treacherously murdered by night, and Perseus, even admiring her beauty in death, cut off her head in this way and brought it back to Greece as a marvel for display.