i64 THE OCEAN 



dead shells and similar creatures in those days 

 any more than it is all covered with the same 

 sort of life to-day. There were vast areas of 

 sandy bottom, immense stretches of mud, 

 cliffs, rocks and coral reefs, and each and 

 every one of these are found preserved in the 

 form of solid rock to-day. Here and there in 

 the ancient bed of the sea, which is now dry 

 land, we find the fossil bones of great sea- 

 monsters; huge marine lizards, gigantic 

 sharks, strange fish and species of whales and 

 similar marine mammals. In every case cer- 

 tain kinds of fossils are found associated, and 

 while some kinds occur through various de- 

 posits covering countless ages, and some are 

 even found alive to-day, yet in most cases 

 each existed for a time, to be succeeded 

 by others slightly different. 



By such means scientists may trace the 

 gradual transition, the slow change and the 

 inevitable evolution that took place among the 

 denizens of the sea. It is in this way that we 

 read the story of the sea, that we know what 

 manner of creatures inhabited it in ancient 

 times, that we know how inconceivably an- 



