250 Formation and Age of the Queensberrys. 



their splintery character under the hammer. On examination the 

 fossils of these shales are found to contain many genera and a large 

 number of species. Yet all these varieties of forms are charac- 

 terised by a simplicity of organism and by a restricted develop- 

 ment of their powers of locomotion and nutrition. For instance, 

 the genus Didymograptus would have a difficulty in procuring food 

 on account of the thecae or mouths being turned downwards. In 

 order to remedy this, Dicellograptus endeavoured to bend its 

 branches upwards. Yet both forms are exceedingly primitive 

 when compared with their succes.sors. Coenograptus gracilis is 

 found in the Glenkiln shales only, and for this reason is regarded 

 as the type fossil of that particular zone. Twenty yards further 

 down from these cherty shales there is another outcrop of shales 

 of an entirely different kind. The strata are of a flaggy nature, 

 and contain grey shales and white bands intercalated with the 

 black — forming one distinct mass of Hartfell shales. The bed of 

 the stream has here a most peculiar and fascinating appearance. 

 By some enormous pressure in a lateral direction the shales have 

 been twisted into a large downward fold resembling a great trough 

 thrown across the. stream. In the very centre of the trough, on 

 the left bank, the wrinkles are so delicate that they may be 

 measured by inches. The great difference between these shales 

 and the Glenkiln group further up stream is not confined to the 

 nature of their material alone but extends also to the fossil con- 

 tents. While .some of the genera of the Hartfell zones are found 

 also in the Glenkiln rocks, yet the great bulk of them are new. 

 The fossils show a higher type of development in various direc- 

 tions, yet all making for the efficiency of the race and the freedom 

 of the individual. This evolution is marked even in the zones 

 showing that the death of one species is replaced by more effective 

 life in the next foot of rock immediately above it. The limbs of 

 the fold contain the beautiful form of Climacograptus Wilsoni, 

 which is peculiar to that band alone, and therefore regarded as 

 the type fossil. The overlying strata in the centre of the trough 

 are recognised by a different zonal form — Pleurograptus linearis — 

 evidently a degenerated survivor of the Glenkiln life. It was the 

 fact of this continued progression of life from the Glenkiln forms 

 to those of the Hartfell period that led Professor Lapworth to 

 regard the latter as a younger deposit in spite of their apparently 

 lower horizon. The structural relations of the groups are 



