THE AGE OF REPTILES 



early geologists used to believe that a complete destruction 

 of all life followed this, the closing stage of the Palaeozoic 

 era, and that a re-creation followed. They would have 

 been confirmed in this belief had they but known that 

 intense cold and glaciation were setting in where the 

 tropics were situated and that the dryness of vast deserts 

 was sweeping away life elsewhere. But we now know 

 that life was not entirely lost; that many species sur- 

 vived, and that others, altering to suit altering conditions, 

 became stronger in the process. Nevertheless, life was 

 greatly impoverished. A census made a few years ago 

 gave the known animal species of the Carboniferous 

 period as 10,000, while those of the Permian period were 

 only 300, or three per cent. Possibly the percentage was 

 larger than that, but still it was small. 



But if the Permian was poor in life it was very in- 

 teresting. The amphibians had been growing in strength 

 during the later stages of the Carboniferous age, and may 

 possibly have been more numerous then than at any 

 other time, for the vast swamps were very favourable for 

 them. They diminished in the "Permian, though the 

 Permian amphibians showed some advances, and began to 

 assume a likeness to reptiles. Perhaps the reptiles may 

 have first appeared in the Carboniferous, but they de- 

 clared themselves in the Permian age. Two great branches 

 of reptiles seem already to have defined themselves ; 

 perhaps they had never formed a common group as 

 reptiles, but had separated while still amphibians. The 

 one bore resemblance to, and were perhaps the forerunners 

 of, the great hosts of lizards, crocodiles, dinosaurs, 



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