30 HAYDEN: GEOLOGY OF THE PROVINCES OF TSANG AND 0. 
small and fragmentary fossils were observed in the rock : these are 
apparently laniellibranchs (of which one may belong to the genus 
Trigonia) and Bryozoa. 
If we turn now to the crinoid limestone of the Lhonak valley, we 
find that although macroscopically it may re- 
Relation to Lhonak i_i ^ c t t i , •, 
limestones semble that oi IsoLhamo, yet its microscopic 
characters^ as described by Professor Garwood,^ 
are quite distinct. Stratigraphically it would also appear to occur 
at a considerable distance below the Jurassic beds of the Yaru 
plain.* Owing, however, to our ignorance of the conditions prevailing 
under the moraines to the north of the Lhonak range, no great 
weight can be attached to this consideration, and if Professor 
Garwood is correct in identifying his crinoid limestone with that of 
Tso Lhamo, the probabilities seem in favour of its being Jurassic 
rather than Palaeozoic as suggested by him.^ 
(c) Kongra La. 
Where the Lachen river, rising from the Drongkhya peaks, skirts 
the northern flanks of Kangchenjhao, it flows 
Jurassic rocks at approximately E.-W. through a broad and open 
Gyamtsonang. rr ^ & r 
valley : to the south are moraines from the 
granite peaks, but to the north is a comparatively low range of hills 
extending from the northern slopes of Chomoyumo to Pauhunri : over 
these run the passes — Kongra and Sibu on the west and Bam Tso 
on the east — which lead from the valley of the Lachen into Tibet ; they 
have already been mentioned by Hooker * as consisting of red and 
1 op. cit. p. 288. 
* See supra p. 24. 
' op. cit. p. 293. 
^ It is evident from Sir Joseph Hooker's description of what he calls the 
Kongralama pass and from the omission of nny reference to Gyamtsonang, the 
lake at the foot of the true Kongra La, that he was misled by the Tibetans into 
believing that Gyaugang, which is in reality some miles lower down the valley, was 
the Kongra La. Htm. Journ,, II, 154, 155. 
( 15' ) 
