Potamius an ecclesiastic of Spanish birth, flourished as bishop of Lisbon in the middle of the 4th century; and if the first of the pieces mentioned below be genuine, he must, in the early part of his career, have been a champion of the Catholic faith. Subsequently, however, he was a zealous Arian, and it is believed that he drew up the document known in ecclesiastical history as The Second Sirmian Creed. The writings usually ascribed to Potamieus are, Epistola ad Athanasiulm Episcopun Alexandrinum de Consubstactialitate Filii Dei, in some MSS. entitled Epistola Potainii ad Athanasium ab Aritais (impetitum?) posquam in Concilio Ariminensi subscripserunt, composed in the year A.D. 355, while the opinions of the author were yet orthodox. The authenticity of this piece, however, which is characterized by great obscurity of thought and of expression, and often half barbarous in phraseology, is very doubtful. It was first published by the Benedictine D'Achery, in his Spicilegium veterum aliquot Scripturm (Paris, 1661, 4to), 2, 366, or 3. 299 of the new edition by Baluze (1717, fol.), and will be foundn in its best form in Galland's Bibliotheca Patrum (Venice, 1769, fol.), 5. 96: — Sermo de Lazaro: — Sermo de Martyrio Essice Prophetae. These are two discourses resembling in style the epistle to Athanasius, long attributed to Zeno, bishop of Verona, and published, without suspicion, among his works, until the brothers Ballerini (S. Zenomis Sermones [ibid. 1739, fol.], p. 297-303) proved that they must be assigned to Potamius, whom however, they supposed to be a person altogether different from the bishop of Lisbon, and belonging to a different age. The arguments which they employ to demonstrate this last position are founded upon the second title of the Epistola ad Athanasium as given above, but this title Galland, Schonemann, and others told to be the blunder of an ignorant transcriber. The Sermones will be found in Galland, and the discussions with regard to the real author in the Prolegomena to the volume, ch. 10, p. 17. See Smith, Dict. of Gr. and Rom. Biog. and Phil. s.v.; Ueberweg, Hist. of Philosophy, vol. 1; II fiele, Conciliengesch. vol. 1.