LIFE ON THE EARTH. 



The numbers representing the several genera in 

 the Csenozoic groups of strata would bear a much 

 nearer proportion to those of the now living species 

 if we had employed the data of Deshayes, and in- 

 cluded European species. The analogy of the Cse- 

 nozoic to the living marine fauna, and the contrast 

 between these and the older systems of life are espe- 

 cially striking in regard to the Gasteropodous genera 

 placed to the right. 



Numerous in a fossil state. 



VARIETY OF THE FORMS OF LIFE IN SUCCESSIVE 

 PERIODS. 



If we select among the marine classes of animals 

 those which are represented in all the great periods 

 of Geology, count the number of species yet disco- 

 vered in them in the British strata 1 , and refer 



1 See Morris's excellent Catalogue of British Fossils, 2nd 

 Edit. 



