48 Records of the Indian Museum. [Vor. VII 
It isof course no new discovery that the fauna of hill-tops 
south of the Ganges valley includes a Himalayan element, and 
a great deal has been written about this fact with reference to 
the mountains of the Madras Presidency. A summary of all the 
more important writings on the subject will be found in the late 
Dr. W. T. Blanford’s classical memoir on the distribution of the 
Indian vertebrates in the Phzl. Trans. Roy. Soc., vol. 194 (B), 
IQOI (p. 422, etc.). 
The generally accepted explanation of distributional pheno- 
mena of the kind is that it is due partly to the transport 
of winged animals or the eggs of non-winged organisms by 
aérial currents and perhaps occasionally by birds, and partly to 
changes in the distribution and extent of the glaciers of the 
higher mountain ranges. Much evidence has been adduced by 
geologists in support of the belief that the glaciers of the Hima- 
layas, at a period not very remote, extended considerably further 
south than they do at present. La ‘Touche,’ however, has 
recently shown that they cannot have extended as far as the 
Ganges valley, except possibly at an ancient geological period. 
It can, I think, hardly be maintained that any of the species 
common to the Himalayas and Parésnath existed in their present 
form at this ancient period, and it seems unnecessary to go far 
back in geological time to search for an explanation of their 
present geographical distribution. There is no reason whatsoever 
to think that the individuals living on Parésnath were ever 
isolated by a ring of ice or driven to the summit by glaciers 
sufficiently extensive to submerge the base of the hill: but it 
must be remembered that the secular movements of glaciers 
are accompanied by profound modifications not only in temper- 
ature but also in humidity, and humidity is perhaps an even 
more important factor in the distribution of reptiles and insects 
than actual temperature. We must suppose that Lygosoma 
stkkimense once lived in the plains as well as or instead of in the 
hills, but that a fallin the atmospheric humidity of the former, 
perhaps due in part to movements of glaciers in the Himalayas, 
drove it up into the E. Himalayas on the one hand and the summit 
of Parésnath on the other, or confined it to comparatively high 
altitudes. 
It is perhaps worth noting that the Himalayan element in 
the fauna of Parésnath appears to be allied to that of the E. 
Himalayas, whereas that in the flora rather shows affinities with 
the flora of Kumaon. The climate is, however, very similar 
to that of the lower slopes of the hills below Naini Tal and we 
may suppose that seeds brought by winds or birds from that 
part of the Himalayan ranges would have a better chance 
of germinating and propagating their species than those from 
the damper forests of Nepal or Sikhim, which are actually 
nearer in space. Hooker says of the flora of Parésnath, which 
1 Geological Magazine (v), vii, p. 193 (1910). 
