676 MR. J. E. MAER AND DE. H. A. NICHOLSON 



shows the green grits and shales of the Browgill Beds. The cliif 

 attains its maximum height near the point where the 1250 feet 

 contour-line crosses the stream, and here a cleft occurs in the cliff 

 which is spoken of in the dialect of the country as a " rake "*. We 

 shall speak of this cleft as " The Eake." In its walls there is an 

 admirable exposure of the lower part of the Browgill Beds, which 

 are slightly displaced by a small fault which has determined the 

 formation of the rake. 



The section seen in this " rake " is represented in figure 2, where 

 the slope of the cliff is exaggerated in order to save space. The bed 

 Ac 4, which corresponds with the Acidaspis-erinaceus zone of Skelgill 

 as will be hereafter shown, is the highest band of the Skelgill Beds. 

 This passes up in the same way as at Skelgill into the pale-green 

 beds of the Browgill group, without the intervention of Graptolitie 

 shales. Two distinct zones of Graptolitie shales occur in the cliff, 

 and it will be convenient to connect with each of them the mass of 

 non-Graptolitic green beds which occurs beneath them. 



Ba. Loiver Browgill Beds. 



Brt 1. The pale shales passing into the blue mudstones of the 

 uppermost Skelgill Beds are 21 feet in thickness without the inter- 

 vention of any black shales in which we have found Graptolites. 

 There is a thin band (under an inch in thickness) at a height of 

 11 feet 6 inches above the top of Ac 4, but we found no Graptolites 

 therein. The shales are pale green, slightly gritty in places, and well 

 laminated. They frequently contain cubic crystals of iron-pyrites, 

 and dendritic efflorescences of oxide of manganese, and are quite 

 similar to the bulk of the Browgill Beds, which present a great 

 uniformity of character wherever developed. 21 feet above the 

 uppermost Skelgill Beds occurs a thin black band, Ba V, weathering 

 to a buff-yellow colour, and crowded along one bedding-plane with 

 tolerably large specimens of Monograptus turriculatus, Barr., which 

 are seen as dark-brown stains upon the rock, but are sufficiently well 

 preserved to show the long spines of the cells in many specimens. 

 The only other Graptolite found here is Monograptus rectus, Lapw. 

 From the great abundance of Monograptus turriculatus, we shall 

 speak of this band with its underlying 21 feet of pale shales as the 

 Zone of Monograp)tus turriculatus, Barr. 



Ba 2. Above this Graptolitie band is another mass of pale shales 

 similar in every respect to those of the turriculatus-zone. They are 

 disturbed at one point by a small monoclinal fold ; but this seems to 

 be unaccompanied by any fracture, so that no shales are apparently 

 faulted out here, and there is a thickness of 19 feet between the 

 black band of the M.-turricidatus zone and the group of Graptolitie 

 shales about to be described. 



These shales, Ba 2', consist of olive-green and grey shales, with a 



* A " rake " is, on a small scale, the same as a " couloir," and is often formed 

 along a prominent joint-plane or line of fault, or by the weathering-out of a 

 dyke. 



