154 



ZOOLOGY 



The age of 

 mammals 



Photograph from Am. Mus. Natural History 

 FIG. 2Q. Skeleton of II sp.-rornis, a Mesozoic bird. 



look familiar; but the vertebrate life would appear 

 wholly strange. 



10. Following the Cretaceous is the Cenozoic, more 

 often called Tertiary, - - the age of mammals. This 

 occupied three or four millions of years only, but it 

 saw the development of the strictly modern fauna and 

 flora. The mammals, which had remained insignificant 

 and apparently not very numerous for millions of years, 

 got a new start. Before very long they produced such 

 an array of new types that we wonder where these could 

 have been developing. Undoubtedly, both in the case 

 of the mammals early in the Tertiary and the flowering 

 plants in the Mesozoic, the apparently sudden exuber- 

 ance of development must be partly illusory. Prepa- 

 rations for these brilliant displays on the stages of 

 Europe and America must have been going on behind 

 the scenes, - - that is to say, in parts of the world 

 whence we have no fossils of the periods concerned. 

 Some day new light will be thrown on these matters, 

 - perhaps in the far north, or in that great Antarctic 

 continent which, though now covered with ice, once 

 supported luxuriant vegetation. 



