C. IAPWORTH ON THE MOFFAT SEEIES. Z{ t 



Hartfell Shales plunge into the grass-grown hill-face at a steep 

 angle. They visibly repose upon the thin-bedded shales and white 

 mudstones of the Pleurograptus zone, which affords abundant, but 

 miserably preserved examples of such characteristic fossils as Lepto- 

 graptus jlaccidus (Hall) and Diplograptus quadrimucronatus. Below, 

 the walls of the score are formed of the thicker-bedded black flags 

 of the zone of Dicranograptus Clingani, which undulate in numerous 

 irregular folds, and yield a few fragmentary specimens of their 

 peculiar species D. Clingani and Climacograptus caudatus. The 

 deepest beds visible are the black, flaggy, and flake-like beds of the 

 zone of Climacograptus Wilsoni, in which the only fossils apparent 

 are the characteristic Discina and fragments of sponges. The 

 remainder of the descent into the bottom of the glen is obscured by 

 the debris washed out of the score. 



That the strata thus hidden from observation are those of the 

 naturally subjacent Glenkiln Shales is at once made evident if we 

 descend the main stream for a short distance. About 200 yards 

 below the foot of the score we encounter a grand group of sections 

 of the beds of that division, all dipping steadily to the southward, at 

 an angle of about 60°, into the face of the steep ridge on the right 

 of the burn. 



No one who has examined the Glenkiln beds of the symmetrical 

 section of Craigmichan Scaurs, where their inferiority to the Hartfell 

 and Birkhill divisions is so unmistakably exhibited, can hesitate to 

 identify with them all the strata exposed in these sections. We 

 have the same peculiar yellowish-grey and white mudstones, 

 here concretionary or shivery and iron-stained, there flaggy and 

 riddled by innumerable burrows of Annelides ; the same thick- 

 bedded grey seams of siliceous rock, weathering like ribs of flint ; 

 and the same hard but easily disintegrating bands of black shale, 

 conspicuous in the light-coloured mass in which they are intercalated. 

 They are here, however, much less altered than at Craigmichan ; there 

 is no direct proof of their repetition by fold or fracture, and at the 

 same time they are all in such a position as to admit of complete 

 study. 



The largest sections occur near the foot of the burn. In the 

 second of these the succession is exhibited which is tabulated on 

 fig. 26, p. 304. 



This is one of the most satisfactory sections of the beds of the 

 ribbed-shales group of the Glenkiln division exposed within the 

 limits of the Moffat district. Its strata lie at gentle angles, are 

 quite unaltered, and admit of thorough examination in situ. 



The fossils of the included black-shale bands embrace a large 

 majority of peculiar Glenkiln forms, chiefly Didymograptus superstes 

 (Lapw.), D. serratulus (Kaill), Ccenograptus gracilis (Hall), C. surcu- 

 laris (Hall), C. explanatus (Lapw.), Dicranograptus ziczac (Lapw.), 

 Dicellograptus sextans (Hall), Diplograptus bimucronatus (Nich.). 



These beds occupy the centre of the band, which at this place is 

 inferred to be about 200 yards in diameter. To the north, as we 

 have seen, they are surmounted by a complete development of the 



