Edge of the Kara-kum desert, in 37° 30' N.
It has in the east the Karnap-chul steppe, covered with grass in early summer, and in the north an intrusion of the Kara-kum sand desert.
Mushketov [1850-1902 ]) Cardium edule, Dreissena polymorpha, Neritina liturata, Adacna vitrea, Hydrobia stagnalis, in the Kara-kum desert, and Lithoglyphus caspius, Hydrobia stagnalis, Anodonta ponderosa and the sponge Metchnikovia tuberculata, in the Kizilkum desert.
But their former tributaries no longer run their full course: the glacier-fed Zarafshan dries up amid the gardens of Bokhara soon after emerging from the highlands; and the Tejen and the Murghab lose themselves in the recesses of the Kara-kum desert.
Through or near this gap flow northwards in parallel courses the rivers Heri-rud (Tejend) and Murghab, until they lose themselves in the desert of Kara-kum.
That the level of Lake Aral was much higher in postPliocene times is proved by the discovery of shells of its characteristic species of Pecten and Mytilus in the Kara-kum Desert, 33 m.