CHAPTER VI 



THE BRONTOSAUR AND ITS COUSINS 



The entire period we have covered so far is called 

 by geologists the ''Ancient Age" of the earth. It 

 embraces more than two-thirds of the life of the 

 earth. If you want to know the correct scientific 

 names, there was first a very long period, probably 

 as long as all the others put together, called the 

 Archcsan Era, which we may call the Very Ancient 

 or Primordial Era. If you take, for convenience, the 

 age of the earth as 100,000,000 years, this part lasted 

 50,000,000 years. There was life only in the later 

 part of it, and no life on land. Then there was a 

 long period of 35,000,000 years (on the same scale) 

 which geologists call the Primary or Palaeozoic 

 (Ancient Life) Era. That is the period we have 

 covered in the last three chapters. In this chapter 

 we are going to survey the "Middle Ages" (the 

 Secondary or Mesozoic Era) of the earth's story. 



And some very quaint mediaeval creatures there 

 were in it, you will say ! It was the age of the giant 

 reptiles, whose hundred-foot-long skeletons you see 

 in museums or works of science. It was the age 

 of the Brontosaur, v»rhich was photographed and de- 



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