FO´RMIO(Φορμίων, Ptol. 3.1.27), a small river, now called the Risano, falling into the Adriatic Sea between Tergeste ( Trieste) and Aegida ( Capo d'Istria), which formed the limit between Venetia and Istria, and consequently at one time the eastern limit of Italy, until Augustus included Istria also under that denomination, in consequence of which the Arsia became the boundary of Italy. (Plin. Nat. 3.18. s. 22.) Ptolemy, however, reckons both the river Formio and the colony of Tergeste as included in Istria; but Pliny's statement is probably correct with regard to the limit as fixed in the time of Augustus, previous to the annexation of Istria to Italy. [ITALIA] Pliny places the river Formio 6 miles S. of Tríeste, which agrees very well with the Risano;and this river has accordingly been identified with the Formio both by Cluver and D'Anville. Walckenaer fixes on a smaller stream flowing into the sea near Muja Vecchia;but this seems too near Trieste, as well as too inconsiderable a stream. [E.H.B]