203 CRITIQUES AND ADDRESSES. [ix. 



Let us now take a step further back in time, and 

 inquire into the relations between the Miocene Fauna 

 and its predecessor of the Upper Eocene formation. 



Here it is to be regretted that our materials for forming 

 a judgment are nothing to be compared in point of extent 

 or variety with those which are yielded by the Miocene 

 strata. However, what we do know of this Upper Eocene 

 Fauna of Europe gives sufficient positive information to 

 enable us to draw some tolerably safe inferences. It has 

 yielded representatives of Insectivora, of Cheiroptera, 

 of Rodentia, of Carnivora, of artiodactyle and perisso- 

 dactyle Ungulata, and of opossum-like Marsupials. No 

 Australian type of Marsupial has been discovered in the 

 Upper Eocene strata, nor any Edentate mammal. The 

 genera (except perhaps in the case of some of the Insecti- 

 vora, Cheiroptera, and Rodentia] are different from those 

 of the Miocene epoch, but present a remarkable general 

 similarity to the Miocene and recent genera. In several 

 cases, as I have already shown, it has now been clearly 

 made out that the relation between the Eocene and 

 Miocene forms is such that the Eocene form is the less 

 specialized ; while its Miocene ally is more so, and the 

 specialization reaches its maximum in the recent forms 

 of the same type. 



So far as the Upper Eocene and the Miocene Mamma- 

 lian Faunae are comparable, their relations are such as in 

 no way to oppose the hypothesis that the older are the 

 progenitors of the more recent forms, while, in some 

 cases, they distinctly favour that hypothesis. The period 

 in time and the changes in physical geography repre- 

 sented by the nummulitic deposits are undoubtedly very 

 great, while the remains of Middle Eocene and Older 

 Eocene Mammals are comparatively few. The general 

 facies of the Middle Eocene Fauna, however, is quite 

 that of the Upper. The Older Eocene pre-nummulitic 



