Passage 5.17.11
κεῖνται δὲ καὶ τρίποδες, ἆθλα δὴ τοῖς νικῶσι, καὶ θυγατέρες εἰσὶν αἱ Πελίου· τὸ δὲ ὄνομα ἐπὶ τῇ Ἀλκήστιδι γέγραπται μόνῃ. Ἰόλαος δέ, ὃς ἐθελοντὴς μετεῖχεν Ἡρακλεῖ τῶν ἔργων, ἔστιν ἵππων ἅρματι ἀνῃρημένος νίκην. τὸ δὲ ἀπὸ τούτου ἀγὼν μὲν ὁ ἐπὶ Πελίᾳ πέπαυται, τὴν ὕδραν δέ, τὸ ἐν τῷ ποταμῷ τῇ Ἀμυμώνῃ θηρίον, Ἡρακλεῖ τοξεύοντι Ἀθηνᾶ παρέστηκεν· ἅτε δὲ τοῦ Ἡρακλέους ὄντος οὐκ ἀγνώστου τοῦ τε ἄθλου χάριν καὶ ἐπὶ τῷ σχήματι, τὸ ὄνομα οὐκ ἔστιν ἐπʼ αὐτῷ γεγραμμένον. Φινεύς τε ὁ Θρᾷξ ἐστι, καὶ οἱ παῖδες οἱ Βορέου τὰς Ἁρπυίας ἀπʼ αὐτοῦ διώκουσιν.
There are also tripods, which indeed were prizes awarded to victors; and there are represented the daughters of Pelias, but the name is inscribed only on Alcestis. Iolaus, who willingly aided Heracles in his labours, is portrayed achieving victory with a chariot drawn by horses. Since that time, the contests held in honour of Pelias have ceased. Heracles stands shown shooting arrows at the hydra, the monster in the river Amymone, with Athena by his side. But because Heracles and his deed are well-known to all, the representation bears no inscription. There is also Phineus the Thracian, and the sons of Boreas pursuing the Harpies from him.