262 C. LAPW0RTH ON THE MOFFAT SERIES. 



in its turn below a shattered group of grey and black beds with 

 white lines, affording M. spinigerus, R. hybridus, &c, the distinc- 

 tive Graptolites of the Upper Birkhill Shales. 



These finally plunge below a thick group of greywackes and flag- 

 stones, forming the upper portion of the cliff, and continued in a 

 prominent series of bosses projecting along the hill-face to the right 

 and left. The grits occupy about 100 feet of the section, and are 

 visibly arranged in a synclinal form, the inverted axis of the fold 

 dipping into the hill at an angle of about 40°. Beyond them the 

 dark shales rise again to the surface in a hollow notch on the face 

 of the steep slope above the actual summit of the cliff. The fossils 

 of these shales are intermingled in the debris of the hollow ; they 

 are all of species peculiar to the Birkhill division. This notch shows 

 at its summit the grey bands of the Upper Birkhill, which for the 

 third time visibly pass below a superior mass of greywackes and 

 shales. These form the small peak of the hill-top and are continuous 

 with the great sheet of greywackes of the surrounding country. 



It is obvious therefore that along this line of section the rocks of 

 this locality are arranged in two main anticlinals. The strata ex- 

 hibited range from the greywackes down into the Barren Mudstone 

 of the Upper Hartfell Shales. Within these limits (exception being 

 made of the apparent absence of the fossiliferous portion of the 

 D.-anceps band), the sequence of rocks and fossils is precisely similar 

 to that in our typical section of Dobb's Linn. 



(b) Description of the /Section along line B-D. (Fig. 3.) 



Before we are able fully to comprehend the physical arrangement 

 of the whole of the rocks exhibited within the Glen, it will be neces- 

 sary to make a second traverse of the beds from the summit of the 

 southern cliff along its southern margin. 



Descending the slope in a south-westerly direction from the point 

 X, we pass over in succession the bands of grit and Birkhill Shales 

 noticed in our former section to the line of the barren mudstone. 

 This passes in a wide and very conspicuous pale-grey band trans- 

 versely across the whole face of the cliff, reaching its southern edge 

 at a point near the centre. 



In our previous section this was the lowest bed exhibited. Here, 

 however, we find a great thickness of subjacent strata. It is imme- 

 diately underlain by a group of thin-bedded shales about 10 feet in 

 total thickness, showing numerous white bands, especially in the 

 upper part, and swarming with D. Morrisi (Hopk.), and Pleurograptus 

 linearis (Carr.), thus agreeing exactly in stratigraphical position, 

 mineralogical character, and fossils with our P.-linearis zone of 

 Dobb's Linn. 



This reposes upon a thickness of about 30 feet of contorted black 

 flaggy shales with fragments of Gorynoides calycularis (Mch.) and 

 Dicellograptus Forchhammeri (Geinitz) in its upper beds, and showing 

 at its base the hard thick-bedded and more siliceous bands of the 

 C- Wilsoni zone. 



