178 Classification of Mammalia. 



VII. MARtSUPIALIA. VIII. EDENTATA. 



a. OARNIVORA. a. TARDIGRADA. 



THYLAGINID.fi. 



DlDELPHIDfi. 

 DASYURIDfi. 



INSECTIVOKA. 



Bradipodid^e. 

 megatherium. 

 b. EDENTATA proper. 



DASYPODIDfi. 



PERAMELIDfi. ORYCTEROPODIDM. 



C I1ERBIVORA. MYRMECOPHAGIDfi. 



PHALANGISTIDJS. MANIDfi. 



Phascolomyidm. c. MONOTREMATA. 



MACROPODIDfi ECHIDNIDfi. 



(Halmaturidce) Ornithorhynchidm. 



IV. § 1. The data relating to the earliest appearance of the 

 class of Mammalia lead us as far back in the earth's history 

 as the period of the oolite. There we find it displaying but 

 a small number of forms under the shape of marsupials, more 

 intimately allied, however, to our opossum than to any of the 

 Australian types. These first representatives of the class in- 

 habited that geographical portion of the globe now called the 

 British Islands. 



The conclusions to which Cuvier had arrived, viz. that the 

 epoch of the appearance of mammals was the tertiary in the 

 series ; his beautiful researches, his remarkable discourses 

 on the revolutions of the globe, were present to the mind of 

 every one. Now came that fossil jaw of an opossum-like 

 animal, which seemed to contradict these philosophical de- 

 ductions. The mammalian nature of the jaw was denied by 

 some, exaggerated by others : its geological position in the 

 oolite was considered as accidental ; but all attempts at 

 rejecting these remains from the class of mammalia have 

 proved unsuccessful ; time and repeated investigations have 

 concurred in shewing that they were true mammals, and 

 that they truly belonged to the oolitic period. And instead 

 of contradicting the formerly ascertained results, these facts 

 now complete the paleeo-hi story of the class, and illustrate 

 most beautifully the gradual introduction of the different 

 groups of the animal kingdom upon the surface of our globe. 

 For it remains true that the class of mammalia acquired a 

 full development during the tertiary epoch only ; the tertiary 

 types were preceded in the secondary epoch by these mar- 

 supials, and in some sort foreshadowed, predicted by them. 



