KHASI HILLS. 137 



limestone were formerly much more numerous, may also be inferred from 



the many sudden and sometimes nearly circular depressions which occur 



on this ridge, and which have obviously been caused by the falling of 



the rocks above into a hollow or excavation below, from which they have 



subsequently been gradually removed. The same process is still in 



operation to produce similar effects, though on a minor scale. The 



waters of the many streams which disappear under- 

 Subterranean streams. 



ground in the adjoining district, are undoubtedly 

 gradually excavating the rocks beneath, and the sujDport being removed 

 from the upper beds these must inevitably fall in, and be themselves 

 gradually removed. ^«^ 



Limestone, very similar to that which occurs at Cherra Poonjee, is 



found in large quantity at a much lower elevation 



Limestone at base of hills. ,,.,,., . , -n -f m 



on the hill side. At the village of Tungwai 



{Tingye) there is a great extent of this rock exposed, and here there are 



large quarries from which many thousands of maunds of this stone are 



annually removed. The limestone stretches from this up the hill side 



for some distance. In general aspect and character it is very similar 



to the limestone at Cherra, but presents in its lower beds some marked 



differences. The occurrence of much larger nummulites, and of a large 



Ovula (0. depressaj are among these. These differences are very much 



less marked at Tungwai than to the East of the Walingtia River, where 



there are immense quarries of limestone. Here the larger nummulites 



(A', spii'o) become much more abundant, and are almost the only fossil 



found in these beds. In other beds above these, the smaller foraminifera 



abound, and also fossils very similar to those found at Cherra Poonjee. 



The abundance of some of these small foraminifera, which form nearly the 



entire mass of some of the beds, give the layers at first sight an oolitic 



(aj In several places in this neighbourhood considorahle streams go underground for 

 some distance. The stream seen in Fig. 13 passes in this way under the cli£f of limestone 

 and coal. 



