4 



AGE OF FLORAS 



[CH. 



Scotland 1 and by those 2 who in recent years have paid particular 

 attention to this question. 



In Wales and some parts of Scotland, the Middle Old Red is 

 wanting, and the higher series rests directly, but with marked 

 discordance, on the lower. This, however, is a complication which 

 now presents no geological difficulty. 



The correlation of the three divisions of the Old Red with the 

 three sub-divisions of the Devon facies of the Devonian is still, 

 to some extent, uncertain. The key to its solution is to be sought 

 in Russia, where the Middle Devonian includes both the Old 

 Red and Devon facies and faunas. Lower Devonian rocks appear 

 to be absent from Russia, but there is little doubt from the 

 evidence of the Middle Devonian as there developed, that the 

 three horizons in the Old Red correspond at least roughly to the 

 three main divisions of the Devonian 3 . 



The following correlation, slightly modified from that given 

 by Freeh 4 , expresses modern views on this point. 



Old Red Facies 



Upper 0>ld Red 



(Cheirolepis, Holoptychius 



and Asterolepis fauna) 



Devon Facies 



Upper Devonian 



Middle Old Red 



(Pterichthys, Coccosteus 



and Osteolepis fauna) 



Lower Old Red 

 (Pteraspis, Cephalaspis 

 and Pterygotus fauna) 



Middle Devonian 



Lower Devonian 



1 Hinxman and Grant Wilson (1902) (see especially Appendix, Part I, 

 Palaeontological, pp. 81-83, by R. H. Traquair); Crampton and Carruthers 

 (1914); Home and Hinxman (1914). 



2 Hickling (1908), p. 396; Macnair and Reid (1896). 



3 Hickling (1908) and the references there quoted. 



4 Freeh (1897), p. 123. 



