THE AGE OF MAMMALS 



unlike the reptiles, bring forth their young relatively 

 mature and nourish and protect them, was contribut- 

 ing to the downfall of the reptiles, though it cannot 

 be considered an actual cause. The mammals' young 

 had a better chance of living and surviving than had 

 the eggs of reptiles. Moreover, the mammals began 

 with superior agility and higher brain-power. It is not 

 surprising, therefore, that the invasion of the mammals 

 resulted in the clumsy, affectionless, small-brained reptiles 

 being driven either into extinction, or into the sedges and 

 rushes, the swamps and lagoons, the coverts of the 

 jungles, the crevices of the rocks, and the various by- 

 ways which the mammals cared least to frequent, and 

 that they have been kept there to this day. 



At first the mammals were not very different in habit 

 or type from one another. Small animals, which, like 

 the shrews, moles, and hedgehogs lived on insects were 

 among the earliest. There were others whose toes were 

 turning to hoofs in order to fit them for fleetness ; and 

 there were some curious creatures called Coryphodons, 

 which were like the modern tapir, though they were 

 tusked like boars. The Coryphodon was a slow beast, 

 with toes like those of an elephant, though it was much 

 smaller. 



In America appeared a small animal not much bigger 

 than a fox-terrier, which was the ancestor of the horse, 

 and of which we shall have more to say. The birds 

 increased, and forms like those of the heron mingled in 

 the swamps with other goose-like birds that kept in 

 their serrated bills some traces of the teeth of their early 



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