202 NERBUDDA DISTRICT. 



It would then appear that during the period when often repeated out- 

 bursts of volcanic matter were accumulating layer upon layer the vast 

 masses of basalt which now form the high table lands, and some of the 

 lofty hills of this district* lakes existed, sometimes of considerable size, 

 in each of which these deposits of the same kind of sediment were accu- 

 mulated! and which were all inhabited by Mollusca of the same 

 species. In the cases mentioned above this sediment was almost exclu- 

 sively a silicious band, • which was subsequently baked by the overlying 

 basalt into the porcelain or flint-like mass which we now find it. 



Sometimes however, though not frequently, a soft mud has been found 



lvine; between two lavers of trap uninfluenced by the 



Intertrappean rock jo j . l 



sometimes not indurated altering action of the molten lava, containing shells 

 identical with those which occur in the hardened beds, and still remaining 

 in the condition in which we must suppose these now altered beds original- 

 ly to have been ; and yet nothing was observed suggesting a cause why 

 results so unlike should have been produced from conditions so similar. 



The locality from whence Dr. Spry first obtained specimens of Physa 

 Prinsepii, near the church at Sagur, is a case of 

 this unindurated intertrappean deposit. Another 

 was observed near Kappa village in the Gondwarra hilis, and a few 

 others mio-ht be mentioned. In all of them, as indeed would be naturally 

 expected, from the friable condition in which the bed is found, the out- 

 crop is soon lost; all traces of it being obliterated by recent denudation 

 and hidden by surface soil, &c. 



Beds of every variety of composition may, of course, be highly indu- 



. L rated or mav remain in a soft state as circum- 



Calcareous mtertrap- J 



pean beds. stanees unconnected with their ingredients shall 



have determined, but all those hitherto spoken of may be considered as 



* See Journal Bombay Asiatic Soc. Vol, V. page 614 for Dr. Carter's views on the 

 subject. 



•j- In this part of the country the beds at different levels are lithologically exactly similar ; 

 elsewhere very dissimilar rock is found in the continuation of the same bed. 



