From BiblePortal Wikipedia

Sedes [1]

(Lat. a seat), a term used by the Latin ecclesiastical writers to denote a bishop's throne, which, with the thrones of his presbyters on each side of it, were arranged in a semicircle above the altar. Some suppose this to have been so arranged in imitation of the Jewish synagogues, in which, according to Maimonides, at the upper end the law was placed in the wall in an arch, and on each side the elders were seated in a semicircle. The bishop's seat was usually covered with some decent material, suitable to the dignity of his office and person. See Bingham, Antiquities of the Christian Church, 1, 299.