Passage 8.27.17
Μεγαλοπολίταις δὲ καὶ Ἡραιεῦσι κατὰ τὰ εἰρημένα ἤδη μοι τοῦ Βουφάγου ποταμοῦ περὶ τὰς πηγάς εἰσιν ὅροι τῆς χώρας. γενέσθαι δὲ τῷ ποταμῷ τὸ ὄνομα ἀπὸ Βουφάγου φασὶν ἥρωος, εἶναι δὲ Ἰαπετοῦ τε παῖδα αὐτὸν καὶ Θόρνακος. ταύτην καὶ ἐν τῇ Λακωνικῇ Θόρνακα ὀνομάζουσι. λέγουσι δὲ καὶ ὡς ἐν Φολόῃ τῷ ὄρει τοξεύσειεν Ἄρτεμις Βουφάγον ἔργα τολμήσαντα οὐχ ὅσια ἐς τὴν θεόν.
As I have already mentioned, near the sources of the Bouphagos river lie the boundaries between the territories of the Megalopolitans and the Heraeans. They say the river got its name from the hero Bouphagos, who was the son of Iapetos and Thornax. This Thornax gives her name also to Thornax in Laconia. They further relate that upon Mount Pholoe, Artemis slew Bouphagos with an arrow for daring unholy deeds against the goddess.