Passage 5.12.1
ὅσοι δὲ ἀνθρώπων τὰ διὰ τοῦ στόματος ἐς τὸ ἐκτὸς ἐλέφασιν ἐξίσχοντα ὀδόντας τῶν θηρίων εἶναι καὶ οὐ κέρατα ἥγηνται, τούτοις ἔστιν ἀπιδεῖν μὲν ἐς τὰς ἄλκας, τὸ ἐν Κελτικῇ θηρίον, ἀπιδεῖν δὲ ἐς τοὺς Αἰθιοπικοὺς ταύρους· ἄλκαι μὲν γὰρ κέρατα ἐπὶ ταῖς ὀφρύσιν ἔχουσιν οἱ ἄρρενες, τὸ δὲ θῆλυ οὐ φύει τὸ παράπαν· οἱ δὲ Αἰθιοπικοὶ ταῦροι τὰ κέρατα φύουσιν ἐπὶ τῇ ῥινί. τίς ἂν οὖν ποιήσαιτο ἔτι ἐν μεγάλῳ θαύματι διὰ στόματος ζῴῳ κέρατα ἐκφῦναι;
But to those who have maintained that the tusks protruding from the mouth of certain creatures are teeth and not horns, it is worth considering the elks—animals found in Celtic lands—and the Ethiopian bulls. The male elks have horns upon their brows, whereas the female does not grow them at all; but the Ethiopian bulls grow horns upon their noses. Who, then, would still regard it as exceedingly strange that an animal might grow horns from its mouth?