Gulielmus Durandus (gulēĕl´məs dyŏŏrăn´dəs), 1237?–1296, French canon jurist and theologian. Educated at the Univ. of Bologna, he served several 13th-century popes in various capacities including those of governor of the papal territories of Romagna and the March of Ancona. In 1286 he became Bishop of Mende. Durandus' Speculum judiciale [mirror of law] (1271, rev. in 1286 and 1291) is an outline of canon, criminal, and civil law that was long studied. His Rationale divinorum officiorum [rationale of the divine office] (c.1286) is an exhaustive treatment, many times reprinted, of the nature and symbolism of the Roman Catholic liturgy. Parts have been translated as The Symbolism of Churches and Church Ornaments (1843) and The Sacred Vestments (1899). His name appears also as Durand, Durantus, Duranti, and Durantis.