482 Dr. J. E. Marr—T/ie Dufton and Eeisleij Groups. 



Our knowledge of the fauna of the Keisley Limestone was 

 largely increased by the papers on that limestone written by 

 Mr. F. Iv. Covvper Reed.^ He there maintains that this fauna shows 

 that the limestone must be removed from the Middle Bala and placed 

 among the Upper Bala Beds — in other words, that it belongs to the 

 Ashgill Group and not to the Sleddale Group. There is no doubt as 

 to the correctness of this contention. Our recent observations show 

 that the beds from which Professor Nicholson and I obtained our 

 ' SiaurocephiJus Limestone ' fossils in the Cross Fell Inlier are in 

 the Keisley Limestone and not above it. Mr. Reed found that the 

 fauna possessed a strong affinity with that of the Staurocephalus 

 Limestone, and we Ciinnot now hesitate to refer the Keisley Limestone 

 to the Staurocephahis Limestone. 



The main results of our work at Easter were : (i) the discovery 

 of the Keisley Limestone in Swindale Beck ; (ii) the discovery of 

 Diifton Beds in the Keisley Quarry ; (iii) the detection of a low 

 zone of Skelgill Beds above the Keisley Beds of the quarry. 

 Attention may first be directed to our work in Swindale Beck. 



In the section down this beck given in the plate appended to the 

 paper " On the Cross Fell Inlier," the Dufton Shales are indicated 

 as passing into the Statirocephalus Limestone and the latter into the 

 Ashgill Shales. This is correct, but the existence of the Keisley 

 Limestone here was not then suspected bj' us. Its non-detection is 

 perhaps pardonable, for in summer the stream at this portion is so 

 well-wooded that it is difficult to see the character of the beds in the 

 dim light. At Easter, however, there is no such difficulty. 



We stated that " at a point where a tributary stream (Ruudale 

 Beck) enters Swindale from the east the Dufton Shales are succeeded 

 by a very calcareous deposit," which we refer to the Statirocephalus 

 Limestone. The junction between the two is, indeed, close to this 

 stream, but the highest beds of the Dufton Group occur on the south- 

 west side of the stream and of a wall which bounds it. These beds 

 consist of dark, almost black, limestone. Above them we measured 

 approximately forty feet of grey compact limestone, of a nodular 

 character, the nodules being most marked towards the base. This 

 limestone exactly resembles that of the Keisley Quarries, where the 

 latter has not become crystalline. In it, as stated above, are the more 

 argillaceous beds, which furnished us with the fossils which we 

 record as belonging to the Stanrocephalus Limestone. The grey 

 and nodular limestone is itself sparsely fossilifevous. We have 

 found therein Ilhcnus and one indeterminable Trinucleus. The 

 occurrence of the latter is interesting, as it has not been found at 

 Keisley. Notwithstanding its presence in Swindale, identity of 

 lithological characters leaves no doubt that this Swindale Limestone 

 is the Keisley Limestone. At the top it seems to pass perfectly 

 conformably into undoubted Ashgill Shales, in which Mr. Fearnsides 

 found Phacops mucronatus. 



Professor Nicholson and I recorded the Statirocephalus Limestone 

 in Billy's Beck. Here it is underlain by Dufton Shales (with 



' Quart. Journ. Geol, Soc, vol. iii, p. 407, uud liii, p. C7. 



