CARBONIFEROUS. 



93 



long- distance, evidently disappearing- from the series, besides which 

 it has hardly a petrological characteristic in common with the o-roup 

 No. 5, though both are arenaceous and partly argillaceous deposits and 

 both, for all useful purposes, unfossiliferous. 



This group. No. 5, is even at its commencement conglomeratic in 

 places. It is occasionally so throughout its extension_, and far to the 

 west, where the groups 3 and 5 lose in thickness greatly, the conglo- 

 meratic character increases, the paste being often earthy and the enclosed 

 fragments large boulders of crystalline rock ; but it is rather uncertain 

 whether these beds may not belong to the " Purple sandstone." The ' 

 average thickness of the group where well seen is from two hundred and 

 fifty to four hundred feet. 



Carboniferous Limestone, &c. 

 No. 6. — We come now to a very interesting formation, the carbon- 

 iferous rocks of the Salt Range which have attracted so much attention 

 The most prominent beds of the group are grey limestones, in colour 

 texture, and very frequently in the general aspect of their organic remains 



"undistinguishable from much of the carboniferon« 

 Limestone. . . «-^ ^^ u^ 



limestone so largely developed in England and 

 Ireland. As in the latter country, magnesian limestones are also com- 

 mon. Shales often predominate at the base, sup 

 other rocks. . ) '=<^^ 



ceeded by yellowish and reddish sandstones with 

 Spirifer and fish remains (teeth, &c.), sometimes containing strono- bands 

 of black coaly sandy shale. The upper parts of these sandstones are 

 in places often highly fossiliferous with Fusilina, 

 Aulosteges, Froductus, Spirifer, &c., and are suc- 

 ceeded by limestones, dolomitic or otherwise, with Goniatifes, Geratites 

 Strophalosia, Athyris, StreptorhyncJms, several species of Productus 

 Spirifer, Retzia, Terehratula, Macrocheilus , Fenestella, Polypora, Rete- 

 pora, Crinoids, and many other of the carboniferous forms, such, for 



„ , instance, as are mentioned in the papers of David- 



Sandy upper strata. . ^ 



son and de Koninck already referred to. The 



( 93 ) 



