Iastus

IASTUS (Ἰαστος), a river which, according to Ptolemy (Ptol. 6.12), was, like the Polytimetus (Kohik), an affluent of the Caspian basin, and should in fact be considered as such in the sense given to a denomination which at that time embraced a vast and complicated hydraulic system. [JAXARTES] Von Humboldt (Asie Centrale, vol. 2. p. 263) has identified it with the Kizil-Deria, the dry bed of which may be traced on the barren wastes of Kizil Koum in W. Turkistan. It is no unusual circumstance in the sandy steppes of N. Asia for rivers to change their course, or even entirely to disappear. Thus the Kizil-Deria, which was known to geographers till the commencement of this century, no longer exists. (Comp. Levchine, Hordes et Steppes des Kirghiz Kazaks, p. 456.)

IASTUS a river mentioned by Ptolemy (Ptol. 6.14.2) as falling into the Caspian between the Jaik and the Oxus. It is only safe to call it one of the numerous rivers of Independent Tartary.