LIFE ON THE EARTH. 65 



beds of the Cretaceous system, and the Csenozoic 

 Series grows slowly through the lowest Eocene to a 

 maximum in the later tertiaries. 



A depression in the maximum occurs in the Palae- 

 ozoic Series of Britain corresponding to the Devonian 

 period, here so largely represented by peroxidated 

 sediments ; another in the Mesozoic period, in the 

 uppermost Oolites, which are poor in comparison with 

 the richer series of Oxford and Bath. These pecu- 

 liarities are represented in the following diagram by 

 a continuous curve, which corresponds to the nu- 

 merical prevalence of life, and represents its rise 

 and fall. Fig. 4. 



R. L, 



