NUMMULITIC SERIES. 59 



mud of less ferruginous kind or sand, and occasionally pebbles, afterwards 

 dear, either precipitating* carbonate of lime, or crowded with lime 

 producing animal organisms, or both causes for the calcareous accumula- 

 tions may have existed. The presence of Niimmuliies has been usually 

 taken to indicate deep seas ; but from several features of the Subdthu 

 nummulitic beds of the Upper Punjab, there may be reasons for doubting 

 whether this were always a necessity of their existence. 



Thickness. — The formation in this district varies greatly in thickness, 

 the latter being of course very much increased if the gypsum and salt 

 below be included. The uppermost calcareous portion is often a narrow 

 band of hard limestone, showing extensively where inclined at a consi- 

 derable angle, but where nearly vertical and crossed by ravines, the,, 

 thickness is always found to be less than the display in the former 

 situations would suggest. In many places the lower earthy part of the 

 group is absent, unless represented in the SheenJcoura of the gypseous 

 series, and for considerable distances the whole of the limestones have 

 disappeared, leaving barely a few thin nodular, calcareous streaks to mark 

 the separation between the red clay zone and the tertiary sandstones 

 and clays overlying the nummulitic limestone group. 



Where the red zone is present, as over most of the district, the 

 lower limits of the limestone may generally be plainly seen, and the 

 passage to the nummulitic clay shale and limestone can occasionally be 

 closely examined, but the upper limits of the group are not always so 

 clearly exposed. A rugged cliff line often occurs along the upper bound- 

 ary owing to the sudden change in the texture of the rocks, and it is 

 rarely, except in the clean cut sections of streams, that the junction 

 between the limestones and sandstones can be inspected. Here the 

 question of conformity or unconformity between the groups recurs to the 

 observer as often as the contact is seen, the facts bearing upon which 

 will be shortly alluded to in the description of the succeeding group. 



Minerals. — The minerals of the nummulitic formation are few : 

 some of the beds have a dolomitic appearance, and in some of the lowest 



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