Augoon, Or Argna, one of the two chief branches of the Amoor river. Under the name of Kerulun or Kerlon, it rises about 30 m. S. E. of the sources of the Onon, S. of the Kentei mountains in Mongolia, and runs N. N. E. through the N. part of the desert of Gobi, about 500 m., to Lake Kulon or Dalai Noor (holy lake). Thence, taking the name of Ar-goon, it flows generally N., with largo bends, about 400 m., between the Russian and Chinese territories, to its junction with the Shilka, forming the Amoor. Its chief affluents are the Khailar, Khalkha, and Gasimoor, the latter running almost parallel with the Shilka.