The Sagartians and Cossseans dwelt in the western portion of the tract, the latter probably about the Siah-Koh mountains, the former scattered over the whole region from the borders of Persia Proper to the Caspian Gates and the Elburz range.

Along its northern edge, east of the Sagartians, were the Parthians, the Arians, and the Gandarians.
occurring in that order as we proceed from west to east.

The Parthians held the country known now as the Atak or "Skirt," the flat tract at the southern base of the Elburz from about Shahrud to Khaff, together with a portion of the mountain region adjoining.

This is a rich and valuable territory, well watered by a number of small streams, which, issuing from the ravines and valleys of the Elburz, spread fertility around, but lose themselves after a short, course in the Salt Desert.

Adjoining the Parthians upon the east were the Haroyu, Hariva, or Arians, an Iranic race of great antiquity, who held the country along the southern skirts of the mountains from the neighborhood of Khaff to the point where the Heri-rud (Arius) issues from the Paropamisan mountains.