RELATION OF BIOLOGY TO GEOLOGICAL INVESTIGATION. . 813 



They all lived under the same <>r closely similar conditions, a ud those 



conditions wore more nearly uniform throughout all geological time 

 than were those under which any other forms of lite existed. Their 

 remains have, therefore, produced a more nearly uniform chronological 

 record. 



Their relations to one another were wholly congruous, while the rela- 

 tions of all of them to all nonmarine faunas and land floras w;is re 



or less incongruous, and in many cases extremely so. 



The formations containing their remains are for the whole world and 

 the whole of the geological scale far in excess of those which contain 

 the remains of any other forms of life, especially the remains of land 

 plants and land animals. 



