220 THE EARTH MADE READY FOR MAN 



While these thousands and thousands of different 

 shells were dropping one by one onto the floor of the 

 ocean and being cast up on the sea beach, there was 

 another form of life growing in the vast ocean, a 

 higher form. These creatures were not covered with 

 shells as were all those which had lived before. They 

 could move freely, they could swim. Can you think 

 what they were? 



Fishes; yes, but strange-looking fishes, not at all 

 like those found now in our seas. Most of them had 

 armor, a hard, bony armor arranged in scales like 

 coat-of-mail, and having these for protection they 

 grew to be of enormous size. The whole ocean seemed 

 to be full of them, as it had been before so full of the 

 shell-covered animals. 



Do you ask, ''How do we know?" Can you not 

 guess that the rocks tell us? 



There the fishes are, in the rocks; caught in the soft 

 clay and mud of the ocean floor when they died, or 

 cast up on the sea beach and covered by the sand. 

 Such extraordinary looking fishes as the rocks pic- 

 ture to us. With their strong armor, something like 

 a turtle's shell, and their huge size, we wonder how 

 they ever moved about' in the sea. 



Gradually, however, there was a change. As the 

 ages rolled by the forms of the fishes became more 

 and more like those we see. For the world changed, 

 and the forms of the animals and plants changed also 

 to accommodate themselves to the changing world. 

 The rocks that were formed under the sea in that 

 later period show us the fishes and the shells as they 

 changed and grew to look like those we now see. 



