CltETACHOUS SERIES. 21 



band continues well represented^ and finally it seems to coalesce and 

 identify itself with tlie bottom rock of the whole series. This union is 

 complete about Surarim ; and the single band continues northward over, or 

 rather through gaps in, a barrier of metamorphic quartzites to Maobe- 

 larka, a mile and a half beyond the disappearance of the nummulitic 

 beds, where it contains a seam of coal four feet in thickness. Such is 

 at least the prima facie view of the section, subject of course to correc- 

 tion from palseontological evidence. It is perhaps presumable that such 

 correction will be made, since this band, here of one to two hundred feet 

 in thickness, seems actually to represent a series ten times as thick at a 

 distance of ten miles to the south. A description of the bottom band 

 will make the case more intelligible, and wiU suggest an argument for 

 the association of all the strata at Maobfelarka, as belonging to the 

 Tipper horizon of the series, equivalent to the Cherra band. An argument 

 for the separation of this bottom band as a group, which has been 

 throughout synchronous and a truly bottom group whatever member of 

 the series it be found associated with, will be mentioned afterwards. 



The bottom rock of the cretaceous series has one character that is 

 nearly constant within the region of the plateau — that of being a coarse 

 conglomerate. The large debris is almost entirely derived from the 

 neighbouring quartzites of the Shillong series ; it is generally sub-angular. 

 From the high level on the shoulders of Laisoplia hiU north of Surarim 

 to the low level 1,000 feet under the terrace of Cherra Punji on the 

 south, this rock forms one continuous band, varying locally from twenty 

 to one hundred feet in thickness. Although thus forming one band, 

 having the same relative position to the overljdng portions of the same 

 series, it physically belongs to every horizon ; and it is at least possible 

 that geologically it does so also — that it would be erroneous to give 

 it a name as a sub-group (as being the bottom rock throughout), 

 implying a date of formation prior to that of all the other rocks 

 of the series ; as for instance, that the conglomerate at Surarim is older 



X ( 171 ) 



