296 C. LAPWOKTH ON THE MOFFAT SEKIES. 



As in numberless instances in the Moffat district, the line of the 

 axis is coincident with that of a longitudinal fault, which here lets 

 in a long, thin, and crumpled wedge of Hartfell Shales between it 

 and the fault bounding the Birkhill beds of the southern cliffs. To 

 the north of the faulted axis excellent sections of the Lower Hart- 

 fell Shales are seen in the northern cliffs, crowded with their charac- 

 teristic fossils, but highly convoluted. The axes of all the small 

 folds which can there be detected rise to the north-east ; and two 

 are of sufficient importance to again bring up to the surface the 

 higher beds of the Glenkiln Shales. 



A third anticlinal of some importance is shown at the north- 

 eastern summit of the north cliff, which also exposes a few feet of 

 the underlying Glenkiln Shales. The axes of all these anticlinals, 

 principal and subordinate alike, are usually faulted, so that in each 

 case only a single leg of the arch is complete at the surface. 



The beds of the lowest of the Hartfell zones, that of Climaco- 

 graptus Wilsoni, are beautifully exhibited immediately above the 

 lines of the Glenkiln Shales ; but the best localities for fossils are 

 those at the extreme ends of the most southerly line. 



The hard black flags of the zone of Dicranograptus Clingani 

 occupy much of the north cliff, in the lower portion of which they 

 may be studied with ease, or in the lateral score near the head of 

 the gorge. 



The thin slaty shales with Pleurograptus linearis are best exhi- 

 bited near the westerly termination of the north cliff, below the 

 fault marked upon the plan. 



The pale beds of the Barren Mudstone make but a poor figure in 

 the sections at this locality. If the orange- coloured mudstones that 

 are exposed between the zones of Pleurograptus and D. vesiculosus, as 

 shown at the back of the little building erected over the mineral 

 spring, include all the beds of this subdivision, it has dwindled down 

 to at least half the thickness it possessed at Dobb's Linn. Similar 

 beds are visible above the Pleurograptus zone, towards the summit of 

 the northern cliffs near the Glenkiln bands marked upon the plan ; 

 and small patches of the same strata are discernible in several other 

 localities. 



The mineral characters and fossils of these zones will be given in 

 the second portion of this paper. 



Glenkiln Shales. 

 A few feet only of the barren portion of the Glenkiln Shales are 

 all that are exhibited at this locality. The hard flinty band at the 

 summit forms a rude cornice or projection running along the western 

 base of the north cliff. It is seen in the same stratigraphical posi- 

 tion in all the remaining anticlinals, and reposes upon several feet 

 of dark grey and pale yellow mudstones identical with those of 

 Glenkiln and Berrybush. It is impossible to separate them by the 

 eye from those of the Barren-mudstone division of Upper Hartfell 

 age ; many of the shales exhibited at the head of the lateral score 

 may belong to either subdivision. 



