1911 Encyclopædia Britannica/Duoviri
DUOVIRI, less correctly Duumviri (from Lat. duo two, and vir, man), in ancient Rome, the official style of two joint magistrates. Such pairs of magistrates were appointed at various periods of Roman history both in Rome itself and in the colonies and municipia. (1) Duumviri iuri (iure) dicundo, municipal magistrates, whose chief duties were concerned with the administration of justice. Sometimes there were four of these magistrates (Quattuorviri). (2) Duumviri quinquennales, also municipal officers, not to be confused with the above, who were elected every fifth year for one year to exercise the function of the censorship which was in abeyance for the intervening four years. (3) Duumviri sacrorum, officers who originally had charge of the Sibylline books; they were afterwards increased to ten (decemviri sacris faciundis), and in Sulla’s time to fifteen (quindecimviri). (4) Duumviri aedi locandae, originally officers specially appointed to supervise the erection of a temple. There were also duumviri aedi dedicandae. (5) Duumviri navales, extraordinary officers appointed ad hoc for the equipping of a fleet. Originally chosen by consuls or dictator, they were elected by the people after 311 B.C. (Livy ix. 30; xl. 18; xli. 1). (6) Duumviri perduellionis, the earliest criminal court for trying offences against the state (see Treason: Roman Law). (7) Duumviri viis extra urbem purgandis, subordinate officers under the aediles, whose duty it was to look after those streets of Rome which were outside the city walls. Apparently in 20 B.C., certainly by 12 B.C., their duties were transferred to the Curatores viarum. From at least as early as 45 B.C. (cf. the Lex Iulia Municipalis) the streets of the city were superintended by Quattuorviri viis in urbe purgandis, later called Quattuorviri viarum purgandarum.
See Fiebiger and Liebenam in Pauly-Wissowa, Realencyc. v. pt. 2.