Passage 1.24.5
ὁπόσα ἐν τοῖς καλουμένοις ἀετοῖς κεῖται, πάντα ἐς τὴν Ἀθηνᾶς ἔχει γένεσιν, τὰ δὲ ὄπισθεν ἡ Ποσειδῶνος πρὸς Ἀθηνᾶν ἐστιν ἔρις ὑπὲρ τῆς γῆς· αὐτὸ δὲ ἔκ τε ἐλέφαντος τὸ ἄγαλμα καὶ χρυσοῦ πεποίηται. μέσῳ μὲν οὖν ἐπίκειταί οἱ τῷ κράνει Σφιγγὸς εἰκών---ἃ δὲ ἐς τὴν Σφίγγα λέγεται, γράψω προελθόντος ἐς τὰ Βοιώτιά μοι τοῦ λόγου---, καθʼ ἑκάτερον δὲ τοῦ κράνους γρῦπές εἰσιν ἐπειργασμένοι.
Everything depicted on what are called the pediments relates entirely to the birth of Athena, while on the rear is the contest between Poseidon and Athena over the land. The statue itself is made from ivory and gold. In the middle of her helmet is placed the figure of a Sphinx—I shall write about what is said regarding the Sphinx when my account comes to Boeotia—and on each side of the helmet are fashioned griffins.