C. LAPWORTH 0^ THE MOFFAT SERIES. 



311 



The only forms I have collected from the zone at this locality 

 are: — 



Dicellograptus moffatensis (?) (Carr.). 

 Dicranograptus Nicholsoni (Hopk.). 

 Climacograptus Wilsoni (Lapw.). 



Climacograptus Scharenbergi (Lapw.). 

 Diplograptus foliaceus (Murch.). 



The same zone is exposed at the foot of Fall-Law Score, near 

 Berrybush, at Craigmichan, and at Cramalt Score, in the valley of 

 the Meggat Water. At Craigmichan it is too much shattered to 

 yield fossils. In the other localities they are present, but are com- 

 paratively rare. 



This zone may be looked upon as marking the age of transition 

 between the two successive formations and life-epochs of Glenkiln 

 and Hartfell. In lithological characteristics it partakes of the 

 peculiarities of both formations. A similar combination is apparent 

 in its included fauna. Every species hitherto detected within the 

 limits of this zone is a survivor from the underlying Glenkiln 

 Shales, while none of the strictly peculiar Hartfell forms have as 

 yet appeared upon the scene. Nevertheless we have unequivocal 

 evidence of the high importance of the unrepresented interval 

 between the period in which the typical Glenkiln fauna was pre- 

 valent and that in which these transitional strata were deposited, in 

 the complete absence from the latter of such striking genera as 

 Coenograptus(Hal\),Didymograptus (M'Coy), Thamnograptus (Hall), 

 &c. In addition to these, numerous species belonging to other 

 genera have totally disappeared, such as Dicranograptus formosus 

 (Hopk.), D. ziczac (Lapw.), Diplograptus Whitfieldi (Hall), D. 

 dentatus (Brongn.), &c. Even of the forms that have survived, 

 several have been remarkably transformed. Dicranograptus ramosus 

 (Hall) has lost its fringe of lateral spines, Climacograptus bicornis its 

 basal disk, while 0. ccelatus has almost certainly been transformed 

 into the form C. Wilsoni. Seven of these survivors become extinct 

 within the limits of the zone, or outlive it for an insignificant 

 period, namely — 



Climacograptus Wilsoni (Lapw.). 



Scharenbergi (Lapw.). 



Diplograptus angustifolius (Hall). 

 tricornis (Carr.). 



Glossograptus Hincksi (Hopk.). 



Harknessi (Nick.). 



Discina, sp. 



ii. Zone of Dicranograptus Clingani (Carr.). — This title is given to 

 the central and most typical mass of the Hartfell Shales. All its 

 strata are of a deep black colour, and there is a total absence 

 throughout of the seams of pale shale and mudstone so common in 

 the neighbouring zones. An additional distinction is furnished by 

 the circumstance that many of its beds are hard and flag-like, 

 forming numerous prominent ribs among the prevailing softer strata. 

 The latter are slaty shales, about one eighth of an inch in thickness. 

 They can be extracted in large plates, are fine-grained, tough, and 

 ring sharply under a, blow of the hammer. There is no distinct 

 mineralogical break between this zone and the preceding, nor is it 

 possible to indicate exactly its superior limit. Eor its base an 



