101 
part 3.] Lydehhr: Fossil, Mammalian Fauna; of India and Burma. 
During the whole of this “ depositing-period” tbe innermost band of the upper 
Tertiaries (Nahans) was probably being gradually upheaved, while its detritus was again 
deposited in tbe outer band: in course of time the elevation of tbe inner regions would 
become so great as to cause the rivers to begin to cut through the outer Siwaliks, and so 
gradually to drain the country ; the Siwalik strata becoming contorted and crushed as they 
were slowly upheaved. This gradual draining of the country and consequent disappearance 
of a great part of the vegetation would, I imagine, have been of itself a power quite 
sufficient to have caused the total extinction of migration of the old Siwalik Fauna from 
these regions without invoking the aid of man or any other living agent. 
Why some genera like Camelopardalis and Hippopotamus, apparently as well fitted as 
Elephas or Rhinoceros to have survived in other parts of India, should have entirely 
disappeared from the country, while others like Sivatherium should have become totally 
extinct, it is useless to conjecture in our present state of knowledge. 
It may be observed that the whole of the Siwalik Mammalia belonged to genera fitted 
for life in tbe plains or in low jungle-dad hills, not barren and lofty mountains : we mark 
the presence of genera like j Elephas, Camelus, Camelopardalis, JEquus, Hippopotamus, and 
Rhinoceros, and note the rareness of Capra, Ibex, Ovis, Nemorhcedus, and similar mountain 
genera. Certain beds in Tibet (General Strachey, sup. cit.), however, presumably of Siwalik 
age, have yielded either an Ovis or Capra : the further exploration of these strata would pro¬ 
bably show a more intimate connection between their fauna and that of Central Asia than is 
found to exist between the latter and the typical Siwalik Fauna. 
APPENDIX A. 
Descriptions of some new or little known Mammalia from the Indian Tertiaries. 
tetraconodon magnum, Falconer. 
This genus was originally founded by Falconer upon two upper molar teeth from Dadupur; 
(‘Palaeontological memoirs’, Vol. 1 page 149) these teeth have apparently been lost; but a 
drawing is given in tbe memoir quoted : no other specimens of the genus have ever been recorded. 
The molar teeth indicate an animal of the hippopotamus family. 
In the present season Mr. Theobald has sent down from the Siwaliks of Asnot in the Potwur 
district a portion of a right mandible of a Hippopotamoid, containing the first and second 
molar teeth, and the ultimate premolar, together with the penultimate premolars of both 
sides of the jaw. The molar teeth of this specimen seem to correspond in general character with 
the molars of Falconer’s Tetraconodon so closely, that I have referred the present specimen to 
the same genus and species. 
The second molar tooth has not yet come into full wear, and is in excellent state for 
description. The crown of this tooth is oblong in shape; it is produced at its angles into four- 
conical or mastoid processes, forming a pair at each eud. A cruciform valley occupies the 
surface of the crown between the four cones; the transverse portion of this valley is the 
widest and deepest; the extremities of this transverse valley extend downwards to the sides of the 
crown. At the central hollow between the four cones there is a bilobed flat tubercle; another 
talon tubercle occupies the hindmost portion of the antei-o-posterior valley ; there is a very small 
tubercle at the outer extremity of the transverse valley. There is no cingulum. 
On the worn surface of the first molar the plane of wear slopes very slightly outwards. 
The resemblance between this penultimate lower molar and the penultimate upper molar of 
Falconer’s specimen (as may be seen by comparing the two descriptions) is complete ; and on the 
evidence of this tooth alone I have united the two specimens under one species. 
