280 C. LAPWORTH ON THE MOFFAT SERIES. 



(ii.) The oldest and deepest beds of each black-shale band occur 

 almost invariably in its central portions ; and, where the succession 

 is unbroken, those of the highest and most recent zone graduate 

 upwards on both margins of the band into the basal beds of the 

 surrounding greywackes. 



These facts point unmistakably to the conclusion that the four 

 parallel black-shale bands of this locality are formed by a repetition 

 of one and the same great group of black shales, and that these 

 owe their recurrence, not to the presence of a series of gigantic 

 faults, but to several parallel folds of the strata. In other words, 

 the rocks of the Moffat Series are the oldest deposits in this area, 

 being inferior in stratigraphical position to the barren greywackes, 

 through which they rise in anticlinal forms (see fig. 15). 



That these relationships hold good everywhere to the south of the 

 Moffat valley will next be demonstrated. 



(b) Black Bands in the Valley of the Yarrow. 



To the north-east of the area last described there are several 

 exposures of the shales and mudstones of the Moffat series. From 

 their position, and from the attitude of the greywackes with which 

 they are associated, there is a strong presumption that they rise to 

 the surface in the prolongations of the anticlinals already noted. 

 No direct evidence, however, is forthcoming upon this point, as the 

 rock-sections are restricted to the miniature cliffs formed by a few 

 of the small upland streams, and the intervening country is covered 

 by turf, gravel, or peat. In the majority of the exposures the 

 strata are too much shattered, or too imperfectly exhibited, to allow 

 us either to give their original sequence or their present relations to 

 the surrounding greywackes. There are, however, two exceptional 

 sections at the extreme north-east of the area, in which the evi- 

 dence upon the second of these points is distinct and unequivocal. 



i. Mount-Benger Burn (fig. 16). — The finest exposure in this direc- 

 tion is afforded by the small stream which derives its title from 



Fig. 16. — Section in Mount-Benger Burn. 



BWl 



Stream. Fence. 



D. Flaggy greywackes and thin grits and shales. 

 Cb. Purple and grey mudstones with seams of black shales and white clays, 



containing Bastrites maximus, Monograptus Halli, &c. 

 Ca. Contorted flaggy black shales with variegated partings. Diplograptus 



palmeus, Monograptus triangularis, M. gregarius, &c. 

 Bcfi. Well-bedded black slaty shales, highly f ossiferous, with Pleurographis 



linearis &c. 

 Ba 2 . Shattered black flaggy shales, with Dicranog raphes ramosus &c. 

 * Space omitted. //. Faults. 



