CEETACEOUS SERIES. 19 



terrace or ledge along- the southern zone of the plateau (such as the flat 

 upon which the station of Cherra Punji is built) ; so that the eye can 

 with the greatest nicety follow the horizon of the upper surface of this 

 sandstone all round the edge of the deep valleys. It is, however 

 evident that this feature may be entirely due to the presence of so easily 

 soluble a rock as the limestone immediately overlying this sandstone, 

 and not to any peculiarity in the sandstone which is often undistinguish- 

 able from the rock above the limestone. It has been shown that the 

 Cherra flat has been in great part, probably altogether, formed by the 

 underground dissolution of this hmestone, and the subsequent removal 

 of the crushed debris, of the overlying beds ; and in fact, where the 

 limestone is absent the ledge I speak of also disappears ; and we find the 

 nummulitic beds in the same sheer cliff with the cretaceous, as about 

 Surarim. It is in such cases that the difiiculty of assigning any dis- 

 tinguishing character between the two sandstones is fiilly experienced. 



If the upper surface of this Cherra band suggests, at least superfi- 

 cially, its separation from the nummuHtic group, there are local relations 

 which would as strongly suggest a separation from the mass of the 

 cretaceous deposits : The only sharply defined line of contrasting de- 

 posits that I could find in the series below the nummulitic limestone was 

 at the base of this Cherra band. In the angle of the cliffs under 

 Maosmai, about 200 feet from the top, the bottom bed of the Cherra 

 band, a massive coarse felspathic sandstone, rests directly upon a fine 

 sandy limestone containing Iryozoa. The contrast of the deposits is 

 very marked ; and in looking from the east at the north and south cliff 

 there is an appearance of pseudo-unconformability along the line of this 

 junction : in the rough strata of the upper band, there is an arrangement 

 as of overlapping each other from the north, as it might be in a diluvial 

 deposit accumulated from that quarter, and in the underl3dng strata, 

 there is an arrangement as of overlapping fi-om the south, as if so 

 banked at the edge of a water basin — the plane of junction overcutting 



( 169 ) 



