ONCHESTUS
1. （Ογχηστός: Eth. Ὀγχήστιος), an ancient town of Boeotia in the territory of Haliartus, said to have been founded by Onchestus, a son of Poseidon. (Paus. 9.26.5; Steph. B. s. v.) It possessed a celebrated temple and grove of Poseidon, which is mentioned by Homer (Ὀγχηστόν θʼ ἱερὸν Ποσιδήϊον ἀγλαὸν ἄλσος, Il. 2.506), and subsequent poets. (Pind. Isthm. 1.44, 4.32; Lycophr. 645.) Here an Amphictyonic council of the Boeotians used to assemble. (Strab. 9. p. 412.) Pausanias (l. c.) says that Onchestus was 15 stadia from the mountain of the Sphinx, the modern Fagá;and its position is still more accurately defined by Strabo (l. c.). The latter writer, who censures Alcaeus for placing Onchestus at the foot of Mt. Helicon, says that it was in the Haliartia, on a naked hill near the Teneric plain and the Copaic lake. He further maintains that the grove of Poseidon existed only in the imagination of the poets; but Pausanias, who visited the place, mentions the grove as still existing. The site of Onchestus is probably marked by the Hellenic remains situated upon the low ridge which separates the two great Boeotian basins, those of lake Copais and of Thebes, and which connects Mount Fay´with the roots of Helicon. (Leake, Northern Greece, vol. 2. p. 213, seq.; Gell, Itiner. p. 125.)
2. A river of Thessaly, flowing near Scotussa, through the battle-field of Cynoscephalae into the lake Boebeis. It was probably the river at the sources of which Dederianístands, but which bears no modern name. (Liv. 33.6; Plb. 18.3; Steph. B. s. v.;Leake, Northern Greece, vol. 4. p. 473.) It is perhaps the same river as the ONOCHONUS(Ὀνόχωνος, Hdt. 7.129; Plin. Nat. 4.8. s. 15), whose waters were exhausted by the army of Xerxes. It is true that Herodotus describes this river as flowing into the Peneius; but in this he was probably mistaken, as its course must have been into the lake Boebeis. (Leake, Northern Greece, vol. 4. p. 514.)