Passage 9.10.6
Καάνθου μὲν ἐνταῦθά ἐστι μνῆμα, Ἀπόλλωνι δὲ παῖδας ἐκ Μελίας γενέσθαι λέγουσι Τήνερον καὶ Ἰσμηνόν· Τηνέρῳ μὲν Ἀπόλλων μαντικὴν δίδωσι, τοῦ δὲ Ἰσμηνίου τὸ ὄνομα ἔσχεν ὁ ποταμός. οὐ μὴν οὐδὲ τὰ πρότερα ἦν ἀνώνυμος, εἰ δὴ καὶ Λάδων ἐκαλεῖτο πρὶν Ἰσμηνὸν γενέσθαι τὸν Ἀπόλλωνος.
Here is the tomb of Caanthus. They say that Apollo had by Melia two sons, Tenerus and Ismenus. To Tenerus Apollo granted the gift of prophecy, while the river received its name from Ismenus. Even previously, however, it was not without a name, being called Ladon before it was named Ismenus after Apollo's son.