THE AGE OF REPTILES 



ichthyosaurs, and flying saurians, which are the most 

 pronounced of the reptiles, and of which we shall have a 

 great deal to say presently. The other group were per- 

 haps the ancestors of the turtles and plesiosaurs which 

 appeared later, and possibly led the way to the mammals. 

 This rapid and diverse spreading out of the reptiles in 

 a period when life as a whole was at a low ebb is not a 

 little remarkable. These creatures seem to show the 

 arrival of a more pronounced form of air-breathing 

 animal; and that may have been the consequence of the 

 presence of more oxygen in the earth's atmosphere. Of 

 the Permian amphibians, one of the most interesting was 

 like the Sphenodon, which still creeps about the northern 

 islands of New Zealand. The most striking of the 

 reptiles was the Naosaurus, a beast-like creature with a 

 high back of spines webbed together like a solid porcu- 

 pine. It was from three to ten feet in length. 



All these changes were brought about by the general 

 withdrawal of the sea, both in the North American con- 

 tinent and in Europe. In both continents there are beds 

 which accumulated fresh water ; in both beds which were 

 laid down in salt lakes or inland seas; and in both beds 

 which were laid down on the floor of seas washing the con- 

 tinents. Great areas seem to have been sometimes dry 

 and sometimes submerged; other and greater areas, 

 bordered by ice and sometimes swept by icy blasts, or 

 subject to burning sun in summer, were deserts such as we 

 are aware of now in Asia or North Africa or mid- 

 Australia, but much larger in extent than any of these. 

 It was in conditions such as these that the ancient 



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