POTAMIUS: Bishop of Olisipo (Lisbon), c. 357. According to Hilary, De synodis, xi., the so-called second Sirmian formula of 357 was drawn up by Hosius and Potamius, while Phbadius (Contra Arianos, iii.) attributes it to Ursacius, Valens, and Potamius. The Luciferian (of San Lucar de Barrameda, Spain) presbyters Faustinus and Marcellinus (Libellus precum) report that Potamius merely signed the formula. This latter work implies, moreover, that Hosius was cited to appear at Sirmium by Potamius, whom Hosius had denounced to the churches of Spain as a heretic. The Luciferian presbyters just mentioned also say that Potamius originally held the Catholic faith but denied it through greed for a piece of land, and that he died while on his way to this property. Catholic orthodoxy is shown in a letter of Potamius to Athanasius (written before 357), and he is mentioned, together with Epictetus of Centumcellæ, as an opponent of Liberius at Rimini in 359 (MPL, x. 681). In the previous year Phbadius had seen in him an opponent who would endeavor to carry through the formula, and records a letter by him of Patripassian tendency. Potamius was the author of two brief treatises in barbarous Latin, preserved by Zeno of Verona (MPL, viii. 1411-15), De Lazaro and De martyrio Isai prophet.