THE AGE OF REPTILES 



divisions red sandstones below and magnesian lime- 

 stones above. Thus there are two types of this Permian 

 formation : the Permian type proper a mixed series of 

 red sandstones, marls, shales, and limestones, with some 

 thin beds of coal, as found in Russia ; and the Dyassic 

 type, as seen in Germany. 



We do not know what brought about the change : 

 though we do know that during it there was great 

 volcanic activity over Europe and that the waning 

 forests of vegetation and the steaming swamps gave 

 place to desert plains. Vegetation sank lower and lower. 

 The forests disappeared or dwelt only in clusters. The 

 soft sappy trees gave place to hardy pines which clung to 

 the plains and the mountains, and other sterner types 

 began to appear, allied to the spruces, yews, and gingko. 

 The gingko tree is one of the oldest of the tree type which 

 now has a living representative. Any reader interested 

 enough in the matter to walk along Royal Hospital Road, 

 Chelsea, will find a gingko tree just outside the Old Physic 

 Garden ; and of course a good many other examples are 

 preserved in botanic gardens. The cycads, offshoots of 

 the ferns, through the strange group of trees known as 

 the cycado-filices, spread through the woods. 



The trilobites, to turn to animal life, all but dis- 

 appeared, though one elegant example remained; the 

 corals were changing ; and the lamp-shells were dropping 

 out. There were a few new species of fishes, but none of 

 any great strength or capacity, and all preserving still the 

 tail which is part of the backbone. There was an all- 

 round impoverishment of life so great, indeed, that the 



228 



