10 MEDLICOTT, SHILLONG PLATEAU. 



It is certain that formations much younger than those now men* 

 tionedj but partaking of the same phenomena of disturbance, will yet 

 be described as occurring in these regions ; at several points along the edge 

 of the hiUs, beds of quite unindurated clay, sand, and gravel, with 

 boulders have been observed, dipping at high angles towards the plains. 

 4. The Nummulitic Series. 



Regarding the upper limits of the nummulitic series I have no 

 more to say than can be gathered from the preceding section. As 

 to its relation to the cretaceous series there is now something definite 

 to be described, and an important correction to be made in the view 

 taken in my former paper. I there lefb the exact horizon of demar- 

 cation still in doubt ; but I stated that the nummulitic overlapped the 

 cretaceous strata on the north. This is not the case, at least in the 

 area that has been examined. I fell into this error by accepting the 

 current assumption that the several local coal seams occurring so nearly 

 on the same apparent horizon did in fact belong to the same formation. 

 I was thus led to conclude that all the beds with the coal in the outlier at 

 Maobelarka were nummulitic, whereas in fact they are aU cretaceous ;^ 

 and I then as a natural consequence found it impossible to trace the 

 horizon of separation. It would have been difficult, when there was not 

 time for a close consecutive examination of the strata, to avoid this 

 error in the section of the Cherra ridge, where the only cretaceous coal 

 that occurs is isolated at a distance from any distinctive nummuhtic or 

 cretaceous rock ; the beds immediately associated with the coal in both 

 series being on the whole very similar to each other. It was this year 

 in the Garo district that I first saw the cretaceous coal where it could be 

 certainly recognised as such ; and it at once occurred to me that this 

 key would solve the difiiculties of the Cherra section ; as I have since 

 proved to be the case. 



* This coal had not been discovered at the time of Mr. Oldham's visit. 

 ( 160 ) 



