Ill] CARBONIFEROUS PERIOD. 39 



V. Devonian. 



By the continued elevation of the Silurian sea-floor, large 

 portions became dry land, and during the succeeding period 

 most of the British area formed part of a continental mass. 

 Over the southern part of England, there still lay an arm of the 

 sea, and in this were laid down the marine sediments which 

 now form part of Devon, and from which the name Devonian 

 has been taken as a convenient designation for the strata of 

 this period. In parts of the northern land, in the region now 

 occupied by Scotland, there were large inland lakes, on the 

 floor of which vast thicknesses of shingle beds and coarse 

 sands (" Old Red Sandstone ") were slowly accumulated ; and 

 it has been shown by Sir Archibald Geikie and others that 

 during this epoch there were considerable outpourings of 

 volcanic material in the Scotch area. 



Farther to the West and South-west there was another 

 large lake in which the so-called Kiltorkan beds of Ireland 

 were deposited. In these Irish sediments, and others of the 

 same age in Belgium and elsewhere a few forms of land plants 

 have been discovered; but it is from the Devonian rocks of 

 North America that most of our knowledge of the flora of this 

 period has been obtained. 



VI. Carboniferous. 



From the point of view of palaeobotany, the shales, sand- 

 stones, and seams of coal included in the Carboniferous system 

 are of special interest. It is from the relics of this Palaeozoic 

 vegetation that the most important botanical lessons have been 

 learnt. 



The following classification of Carboniferous rocks shows 

 the order of succession of the various beds, and the nature of 

 the rocks which were formed at this stage in the Earth's 

 history. 



