Passage 9.21.1
εἶδον δὲ καὶ ἄλλον Τρίτωνα ἐν τοῖς Ῥωμαίων θαύμασι, μεγέθει τοῦ παρὰ Ταναγραίοις ἀποδέοντα. παρέχονται δὲ ἰδέαν οἱ Τρίτωνες· ἔχουσιν ἐπὶ τῇ κεφαλῇ κόμην οἷα τὰ βατράχια τὰ ἐν ταῖς λίμναις χρόαν τε καὶ ὅτι τῶν τριχῶν οὐκ ἂν ἀποκρίναις μίαν ἀπὸ τῶν ἄλλων, τὸ δὲ λοιπὸν σῶμα φολίδι λεπτῇ πέφρικέ σφισι κατὰ ἰχθὺν ῥίνην. βράγχια δὲ ὑπὸ τοῖς ὠσὶν ἔχουσι καὶ ῥῖνα ἀνθρώπου, στόμα δὲ εὐρύτερον καὶ ὀδόντας θηρίου· τὰ δὲ ὄμματα ἐμοὶ δοκεῖν γλαυκὰ καὶ χεῖρές εἰσιν αὐτοῖς καὶ δάκτυλοι καὶ ὄνυχες τοῖς ἐπιθέμασιν ἐμφερεῖς τῶν κόχλων· ὑπὸ δὲ τὸ στέρνον καὶ τὴν γαστέρα οὐρά σφισιν ἀντὶ ποδῶν οἵα περ τοῖς δελφῖσίν ἐστιν.
I also saw another Triton among the marvelous sights of the Romans, smaller in size than the one at Tanagra. Tritons have an appearance as follows: upon their heads is hair resembling that of marsh frogs, similar in color and in that none of the individual hairs can be separated from the others. The rest of their bodies are covered by thin scales, as rough as those found on a shark. Beneath their ears they possess gills, the nose is like that of a human, but the mouth is wider and furnished with teeth like those of a wild beast. Their eyes seem to me to be greenish-grey. They have hands, fingers and nails shaped similarly to the shells of sea-snails. From beneath their chest and belly extends a tail instead of feet, like those of dolphins.