AUDUS(Αὐδος), a river of Mauretania Caesariensis (aft. Sitifensis), falling into the Sinus Numidicus ( G. of Boujayah). It is placed by Ptolemy (Ptol. 10′ W. of Igilgilis ( Jijeli), a position which identifies it, according to Pellissier, with a river called Wad-el-Jenan, not marked on the maps. If so, the promontory Audum (Αὖδον), which Ptolemy places 10′ W. of the Audus, would be C. Cavallo. (Ptol. 4.2. § § 10, 11). But, on the other hand, Ptolemy seems to make Audum the W. headland of the Sinus Numidicus ( C. Carbonor Ras Metznkoub); and, if this be its true position, the Audus might be identified with the considerable liver Sumeim, falling into the gulf E. of Boujayah, and answering (on the other supposition) to the Sisar of Ptolemy. Mannert solves the difficulty by supposing that here (as certainly sometimes happens) Ptolemy got double results from two inconsistent accounts, and that his Sisar and Audus are the same river, and identical also with the USAR of Pliny. Perhaps the two names, Audus and Sisar (or Usar), may belong to the two great branches of the Sumeima, of which the western is still called Adous, and the other Ajeby. (Mannert, vol. x. pt. 2. p. 411; Pellissier, Exploration de l'Algérie, vol. vi, p. 356.)
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