ON THE STOCKDALE SHALES. 665 



(i) The uplDermost Ashgill Shales are marked by a band of cal- 

 careous nodules. These shales pass up conformably into the over- 

 lying beds (Lower Skelgill Beds). 



(ii) The Lower Skelgill Beds are divisible into two zones : — 



(1) A limestone, one foot in thickness, containing ^^r^z/^^j^t^^rwosa 

 and other fossils : = Atryim-Jlexuosa Zone. 



(2) A set of hard, calcareous shales, of which at least 9 feet G 

 inches, are seen, to which we must add three or four feet more if 

 the beds with Dimorpliograptus Siuanstoni, Lapw., are different from 

 those with numerous D. confertus, Nich. These shales contain abun- 

 dance of Dimorpliograptus confertus, !Nich., along with Monograptus 

 revolutus, Kurck, Diplograptus vesiculosus, Mch. &c. :=I)imorpJio- 

 graptus-confertus Zone. 



(iii) A strike-fault occurs everywhere in the gill between this 

 zone and the overlying Middle Skelgill Beds, so that the thickness of 

 the Dimorpliogi'dptus-conferius Beds and of the lowest member of the 

 Middle Skelgill Beds can never be ascertained in this stream. 



(iv) The Lower Skelgill Beds, which are harder and more calcareous 

 than the succeeding Graptolitic bands, are always continuous with the 

 underlj'ing Ashgill Shales, and are therefore usually found on the right 

 bank of the stream, whilst the succeeding beds are almost entirely 

 confined to the left bank, as the stream has naturally worked its 

 way along the strike-fault for the greater part of this portion of its 

 course. 



Kb. Middle JSJcelgill Beds. 



(1) Starting again at the Lower Bridge, and examining the dis- 

 continuous rock-exposures in the wooded bank of the stream above 

 the breccia of the strike-fault (which, it will be remembered, oc- 

 curred above the D.-conferfus Beds of the cliff immediately below 

 the bridge, and on the left bank of the stream), we find black 

 shales, with a considerable quantity of pyrites, and containing manj 

 Graptolites in high relief. Just above the bridge, a thickness of 

 four feet of these beds used to be visible, below some blue mudstones 

 from which Graptolites are absent. The beds are better disi)layed 

 in the small cliffs which occur on the left bank of the stream at 

 various points in the wood, commencing about halfway between the 

 Lower Bridge and the first tributary from the north, and continuing 

 to the junction of the main beck with this feeder. The blue mud- 

 stones devoid of Graptolites are seen here, and below them, and 

 between them and the strike-fault so frequently alluded to, we get 

 the following section in descending order : — 



ft. in. 



Black Graptolitic shales 3 6 



Pale green band i 



Black Graptolitic shales 1 3 



Non-Graptoli tic striped bed 6 



Black Graptolitic shale 2 seen above the fault. 



Total 7 3^ seen. 



