CHAPTER IX. 



THE MESOZOIC AGES (continued). 



THE waters of the Mesozoic period present features 

 quite as remarkable as the land. In our survey of 

 their teeming multitudes, we indeed scarcely know 

 where to begin or whither to turn. Let us look first 

 at the higher or more noble inhabitants of the waters. 

 And here, just as in the case of the greater animals 

 of the land, the Mesozoic was emphatically an age of 

 reptiles. In the modern world the highest animals 

 the sea are mammals, and these belong to three great 

 and somewhat diverse groups. The first is that of the 

 seals and their allies, the walruses, sea-lions, etc. The 

 second is that of the whales and dolphins and por- 

 poises. The third is that of the manatees, or dugongs. 

 All these creatures breathe air, and bring forth their 

 young alive, and nourish them with milk. Yet they 

 all live habitually or constantly in the water. Be- 

 tween these aquatic mammals and the fishes, we have 

 some aquatic reptiles as the turtles, and a few sea- 

 snakes and sea-lizards, and crocodiles ; but the 

 number of these is comparatively small, and in the 

 more temperate latitudes there are scarcely any of 

 them. 



All this was different in the Mesozoic. In so far as 

 we know, there were no representatives of the seals 



