ONCEIUM(Ὄγκειον), a place in Arcadia upon the river Ladon, near Thelpusa, and containing a temple of Demeter Erinnys. (Paus. 8.25.4; Steph. B. s. v.) The Ladon, after leaving this temple, passed that of Apollo Oncaeates on the left, and that of the boy Asclepius on the right. (Paus. 8.25.11.) The name is derived by Pausanias from Oncus, a son of Apollo, who reigned at this place. Leake supposes that Tumbíki, the only remarkable site on the right bank of the Ladon between Thelpusa and the Tuthoa, is the site of the temple of Asclepius. ( Morea, vol. 2. p. 103.) Other writers mention a small town ONCAE (Ὄγκαι) in Arcadia, which is probably the same as Onceium. (Tzetzes, ad Lycophr. 1225; Etym. M. p. 613; Phavorin. s. v.)