The great central province of Nejd occupies all inner Arabia between the Nafud and the southern desert.
Of birds the ostrich is found in the Nafud and in the W. Dawasir.
Owing to the great extent of the Nafud desert, the formation of sand-dunes is exemplified on a proportionate scale.
The northern edge of this great desert follows very nearly the line of the thirtieth parallel, along which The Nafud.
In the south of the Nafud, where Huber found the prevailing wind to be from the south, the falks are turned in that direction.
East of Nejd a strip of sandy desert 50 m. in width extends almost continuously from the great Nafud to the Dahna.