C. LAPWOHTH ON THE MOFFAT SERIES. 



289 



is visible along the lower course of the small stream called Prenchland 

 Burn. The section at this locality possesses an additional interest 

 for geologists from the circumstance that it was the only section of 

 the Moffat Series examined personally by Sir Roderick Murchison. 

 He described the general appearances of the pyritous mudstones and 

 the surrounding greywackes with some minuteness, noticing espe- 

 cially their greatly disturbed condition, but carefully refrained from 

 hazarding any opinion as to their interrelationships. (Q. J. Gr. S. 

 vol. vii. p. 161.) With our present experience we can now unravel 

 the succession with comparative ease and certainty. 



Prom the point at which the black shales emerge from 

 below the Permian conglomerates of the vale of the Annan to that 

 where they finally subside beneath the flagstones and greywackes of 

 the Gala group is about three fourths of a mile. Midway between 

 these points, however, the greywackes occupy the stream-course for 

 a distance of about one fourth of a mile, so that there are actually 

 two separate exposures of black shales. The general direction of the 

 stream is almost coincident with the strike of the rocks, and conse- 

 quently only a very small proportion of the whole of the Moffat Series 

 is exposed. On both sides the greywackes approach nearly to the 

 bottom of the hollow, the black shales being confined to the bed and 

 banks of the burn. 



The two exposures show precisely the same succession, viz. all 

 the Eirkhill Shales above the zone of Diplograptus acumiaatus ; but 

 the lower exposure affords the most satisfactory sections of the beds, 

 while the upper yields the more numerous fossils. 



In the lower exposure the beds, which are highly contorted, show 

 the usual irregular but prevailing dip to the N.N.W. Their ar- 

 rangement may be gathered from the accompanying plan. Some 

 hard black flags near the centre of the exposure yield Diplograptus 

 vesiculosus and its associates, and pass into softer and more pyritous 

 strata, which in their turn are in contact with the grey and black 

 shales of the Upper Birkhill group. To the south the latter are 

 inverted, but are seen to pass gradually into the overlying grey- 

 wackes. To the north, where a small waterfall marks the summit 

 of the formation, a small fault occurs, and the dark seams here are 

 highly fossiliferous, and yield beautifully preserved specimens of 

 such characteristic forms as Monograptus JBechi (Barr.), M. Halli 

 (Barr.), M. Hisingeri (Carr.), and -Diplograptus folium (His.). 



The higher exposure adds nothing to our physical evidence, but 

 furnishes us with an abundance of Birkhill fossils. To the south 

 its beds are faulted against the greywackes ; to the north the point 

 of junction is not visible. They clip almost invariably to the N.N.W., 

 but are, in truth, arranged in several inosculating anticlinal forms. 

 In all, the predominating strata are those of the Lower Birkhill 

 Shales ; the peculiar pyritous beds of the M.-gregarius zone are espe- 

 cially conspicuous, swarming with their characteristic Graptolites. 

 The grey- shale group is also visible for some distance ; but only a 

 few of its fossils have been obtained. 



ii. Garple Spa (PL XIII. Plan J).— To the west of the valley of the 



