PRE-JURASSIC SEDIMENTARIES. 23 
geology, and it is greatly to be deplored that it is not possible 
to extend observations eastwards through Nepal and Bhutan. Under 
jjrcsent circumstances the value of the Dothak series is still further 
enhanced, since it constitutes the only known outcrop of presumably 
Triassic rocks throughout the whole extent of the eastern Himalaya. 
Although the Dolhak series is the only one met with during the 
recent expedition that can be safely asserted to include part at least of 
the Triassic system, there is another area considerably further to the 
west in which that system is probably represented. This is the snowy 
range which runs from Chomoyumo westw'ards to the frontier of Nepal, 
and which forms the northern boundary of the valley of Lhonak.' 
Unfortunately this range could not be visited from Kampa dzongj but 
an excursion along its northern slopes from the neighbourhood of the 
Naku La to the village of Mong-go, indicated the possible value of a 
careful examination of the range. The line followed lay across the 
northern slopes which form a wide inclined plane of glacial debris, cut 
into cafions, often several hundred feet deep, by the streams flowing 
from the snow-fields to join the Yarn river: the beds of the streams are 
full of rounded boulders of dark grey limestone, quite unlike any of 
the Jurassic or younger rocks and curiously like the Upper Triassic 
limestones of other parts of the Himalaya. No fossils were found in 
the boulders of this limestone, and lithological resemblance in two 
such widely separated areas as Spiti and Lhonak, especially in view of 
the dissimilarity in the intermediate areas, is of no value as a means of 
correlation. 
To the north of the range are shales and limestones, the former of 
lower Jurassic age, and as the limestones of the range appear to dip to 
the north they are presumably the older, and it is therefore possible 
that Triassic beds may occur among them. 
This vieWj however, is not confirmed by the very interesting observa- 
tions made in the Lhonak valley by Professor 
Mesozoic beds in Lhonak. 
Garwood, who found a series of altered lime- 
stones and sandstones at the head of the Langpo Chu, to the south 
' For convenience of reference this may be called the Lhonak ranoe. 
( ) 
