On the Classification of Mammalia. 181 



number in the pliocene, and finally the living representatives 

 are still less numerous. So that pachydermata are in the 

 period of their decline, as well as the edentata. 



Now as far as is known, these two groups, Pachydermata 

 and Edentata, are the only ones in the class of Mammalia 

 whose circle of activity has been exhausted in geological 



The two series which we have established among pachy- 

 derms will have to be carefully studied geologically. 



The oldest remains known of Sirenidia have been discovered 

 in the lowest beds of the miocene period. 



The oldest remains of ruminants known, belong to the 

 middle strata of the miocene period. 



Cetaceans are contemporaneous with the ruminants ; it 

 being always understood that we speak of the actual state of 

 our knowledge. 



Rodentia, which we consider the highest amongst Herbi- 

 vora, are foreshadowed by Marsupialia, the second synthe- 

 tical type. Rodentia make their first appearance at the be- 

 ginning of the eocene period, the first of the tertiary epoch. 



And so do the Carnivora proper and Pinnipedia, parallel in 

 their genetical development ; although zoologically speaking, 

 Pinnipedia are lower, and synthetise the two groups of car- 

 nivorous digitigrades and plantigrades. 



Insectivora, which are shadowed by both Edentata and Mar- 

 supialia, are not known in the eocene : their remains, hitherto 

 found, belong to the miocene and strata above. 



Quadrumana and Cheiroptera have left some of their re- 

 mains in the middle strata of the eocene period. 



The annexed diagram is intended to sketch out the history 

 of the class of Mammalia, prior to the epoch of mankind. 



§ 4. If we look now at the geographical distribution of 

 Mammalia, which is regulated by laws, we may point out 

 some facts of a very striking interest, and which corroborate 

 the foundation of our classification. 



The globe and the animal kingdom were created for one an- 

 other ; the globe, however, was made for the kingdom, matter 

 being subordinate to life. During each of the geological ages, 

 and even during each period or era, the physical features of 

 the globe have assumed a peculiar character. The animal 



