GEOGRAPHICAL INTRODUCTION. 
By N. ANNANDALE, D.Sc., F.A.S.B., Director, Zoological Survey of 
India. 
(With Plates I-I1.) 
Seistan and the Helmand River. 
The Persian district of Seistan, at periods in its history an 
independent state and at others a part of Afghanistan, lies roughly 
between long. 61° and 62° E., lat. 30°50’’ and 31°50” N.; but its 
precise boundaries are not delimited to the west and south. It 
consists of the delta of the R. Helmand and the Hamun or basin 
into which that river flows. These lie, surrounded on all sides by 
stony desert, in a depression less than 2000 feet above sea level. 
The Helmand rises in the Hindu Khush in about lat. 68°40” and 
long. 34°30” and flows for three hundred miles through the moun- 
tains of Afghanistan, receiving many tributaries on its way. It 
then debouches on the desert plateau of Registan and, some 
distance after doing so, is joined by its largest tributary, the 
Arghandab. The course of the united waters, which flow in a 
deep bed through the desert, is S.S.W. for some seventy miles. 
They are then deflected by a small range of hills through which 
they have been unable to cut their way, and continue westward, 
with a distinct southward bend, for about another hundred and 
fifty miles. Then, on reaching the southern limits of the old delta, 
the river breaks up into innumerable channels, partly natural, 
partly artificial, which turn northwards. In these channels, 
the chief of which is ultimately known as the Rud-i-Pariun, 
much of the water is dissipated, but what remains finally drains 
westward into the Hamun-i-Helmand or Hamun-iSeistan, a large 
basin (or rather series of basins) which occupies a- considerable 
but extremely variable area. After the junction of the Arghan- 
dab and the Helmand very little additional water, not nearly 
enough to compensate for evaporation, enters the system ; for the 
desert is practically rainless, even in Seistan the rainfall is only a 
