Passage 8.25.7
τὸ μὲν δὴ τῆς Ἐρινύος τήν τε κίστην καλουμένην ἔχει καὶ ἐν τῇ δεξιᾷ δᾷδα, μέγεθος δὲ εἰκάζομεν ἐννέα εἶναι ποδῶν αὐτήν· ἡ Λουσία δὲ ποδῶν ἓξ ἐφαίνετο εἶναι. ὅσοι δὲ Θέμιδος καὶ οὐ Δήμητρος τῆς Λουσίας τὸ ἄγαλμα εἶναι νομίζουσι, μάταια ἴστωσαν ὑπειληφότες. τὴν δὲ Δήμητρα τεκεῖν φασιν ἐκ τοῦ Ποσειδῶνος θυγατέρα, ἧς τὸ ὄνομα ἐς ἀτελέστους λέγειν οὐ νομίζουσι, καὶ ἵππον τὸν Ἀρείονα· ἐπὶ τούτῳ δὲ παρὰ σφίσιν Ἀρκάδων πρώτοις Ἵππιον Ποσειδῶνα ὀνομασθῆναι.
The statue of the Erinys holds what is called a cista, and in her right hand a torch; we estimate the figure to be about nine feet tall. The statue of Lousia appeared to be six feet in height. Those who think that this statue of Lousia represents Themis rather than Demeter should know they are holding a mistaken opinion. It is said that Demeter gave birth, by Poseidon, to a daughter whose name they do not consider proper to reveal to the uninitiated, and also to the horse Areion. For this reason, they say, the Arcadians first named Poseidon Hippios ("Horse-god").