Passage 7.23.2
μετὰ δὲ οὐ πολὺν χρόνον οὔτε ὡραῖος ἔτι ἐφαίνετο Σέλεμνος οὔτε ὡς αὐτὸν φοιτήσειν ἔμελλεν ἡ νύμφη, Σέλεμνον δὲ μονωθέντα Ἀργυρᾶς καὶ τελευτήσαντα ὑπὸ τοῦ ἔρωτος ἐποίησεν Ἀφροδίτη ποταμόν. λέγω δὲ τὰ ὑπὸ Πατρέων λεγόμενα. καὶ---ἤρα γὰρ καὶ ὕδωρ γενόμενος Ἀργυρᾶς, καθότι ἔχει καὶ ἐπὶ τῷ Ἀλφειῷ λόγος Ἀρεθούσης ἔτι ἐρᾶν αὐτόν---δωρεῖται καὶ τῷδε Ἀφροδίτη Σέλεμνον·
But soon after, Selemnos no longer appeared handsome nor likely that the nymph would visit him again. Having become lonely and dying from love after Argyra left him, Selemnos was transformed by Aphrodite into a river. I recount here what is told by the people of Patrae. And even as water he still loved Argyra, just as the tale is told that Alpheios continues still to love Arethousa. Aphrodite granted Selemnos an additional gift: