502 PROF. H. A. NICHOLSON AND MR. J. E. MARK ON 



considerable attentiou to the Skiddaw Slates of the more central 

 ])ortion of the Lake District before their minute subdivisions can 

 be satisfactorily determined. 



We believe that the oldest rocks of the Cross Fell Inlier occur in 

 the extreme north-eastern portion of the inlier in the neighbourhood 

 of Cuns Fell, where they are probably separated by yet another 

 N.W. to i^.Yj. fault from the newer rocks to the west. Here, in the 

 course of Dry Sikc and Hungrigg Sike, a series of greenish shales 

 are seen dipping in a general south-westerly direction at a high 

 angle. These shales furnished the obscure fossil described bj- one 

 of us in the Geol. Mag. for 1869 (pi. xviii. d) as possibly of vege- 

 table origin ; but this affords no clue as to the precise age of the 

 series. They are succeeded to the south by blacker shales and 

 grits which bear considerable resemblance to the older Skiddaw 

 Slates of the Lake District, and they are probably contemporaneous 

 with these, though no fossils are recorded from them in this area, 

 and we have found none. Similar beds are again seen farther 

 south at Brownber, and in the streams adjoining it, and they 

 continue over a considerable part of the ground east of the Knock 

 Pike-Flagdaw .Fault, as far south as Roman Fell. At Brownber 

 (and in a few other places such as Murton Pike and the neighbour- 

 hood of Keisley) they have undergone great disturbance, and are 

 ])enetrated by numerous quartz- veins, which are folded with the 

 strata, causing considerable changes in the rocks, as notified by one 

 of us at the Newcastle meeting of the British Association in 1889. 

 Mr. Alfred Harker has kindly examined sections of these rocks for 

 us, and has furnished us with an appendix to our pax)er, giving 

 descriptions of these and other rocks of this area. 



ISText in order of age we would place the black shales, which 

 occur repeated thrice, firstly in Ashlock Sike and the neighbour- 

 ing tracts east of Ousby, next in EUergill and the adjoining ground 

 under Cross Fell, and lastly in the course of Knock Ore GiU. 

 These strata — which we term the " EUergill beds '' — have yielded 

 an abundant harvest of fossils, of which a list is given in Prof. 

 Lapworth's paper on " the Geological Distribution of the Phab-^ 

 dophora '' *, most of them being well-known Upper Arenig forms. 

 At the summit of the beds referred to the Skiddaw Slates, Mr. J 

 G. Goodchild locates his " Milburn Group," consisting, as he has 

 pointed out, of a series of slates alternating with submarine tuffs. 

 These are excellently disijlaycd in Wythwaite Hole, and in the 

 streams to the south of it, where they are also intercalated with 

 lavas. Few fossils have yet been discovered in them, but Mr. Good- 

 child records Didymogrcq^ttis MurcJiisoni^ Boeck, and we have found 

 Dij)logra2?tus dentatus, Brongn., so that the beds are probably closely 

 related to the EUergill Group, from which they differ in the occur- 

 rence of the volcanic material. Mr. Goodchild rightly insists upon 

 the importance of his discovery as throwing light upon the vexed 

 question of the relationship of the Skiddaw Slates to the volcanic 



* Ann, & Mag. Nat. Hist. ser. 5, vol. iii. p. 23, sep. cop. 



