PREVIOUS TO THE LAST GEOLOGICAL REVOLUTION. 381 



these modifying circumstances into consideration, I think 

 that a comparison between the extinct fauna of tropical 

 America, and of extra-tropical Europe will not be without 

 use, 



[Dr. Lund here refers to a Table, marked 4, which, as he 

 says in a note, '' represents the state of our knowledge on 

 this point of fossil zoology at the time when Cuvier con- 

 cluded his inquiries respecting it ; and I am not aware that 

 there have been any subsequent additions, of essential im- 

 portance, with regard to number of species/^] 



If we now compare this description with the list of South 

 America's extinct mammals, we see that the latter exceeds 

 the other in number, both of species and genera ; and if we 

 further lay in the scale all the circumstances to which I have 

 just drawn attention, it is very clear that we must allow to 

 the tropical region of America a far richer fauna in the an- 

 cient period, than to the extra-tropical portion of the Old 

 World. Such a disproportion between these two zones, with 

 reference to their animal productions, can only be explained 

 by the supposition of a corresponding difference in temper- 

 ature ; so that we see it results from these considerations as 

 a very probable consequence, that at that epoch also, as now, 

 the surface of our planet presented a difference of tempera- 

 ture, according to geographical latitude, in other words, cli- 

 matic distinctions had already begun to act. 



But as surely as the extra-tropical portions of our globe 

 were already at that period inferior in temperature to the 

 tropical, equally certain is it that they then enjoyed a higher 

 temperature than is now allotted to them. When we see 

 that the class of extinct mammals, found in the extra-tro- 

 pical zone of the Old World, surpasses that now living there 

 in variety and abundance of forms, as well as for the most 

 part in number of species ; when we also see that the prin- 

 cipal of these forms are such as in the present creation are 

 peculiar to the tropics ; surely the most prejudiced person 

 must be led to conclude that the temperature of those which 

 are now the temperate and frigid zones, must have formerly 

 more or less corresponded to the actual heat of the tropical 



^ It is not my intention here to revive the much-canvassed subject of the 

 haiiy Elephants and Rhinoceros of Siberia ; but I cannot forbear remark- 

 ing, how very hasty they were who endeavoured at once to draw from this 

 phsenoraenon the conclusion that the cHmateof Siberia cannot have changed. 

 In the first place, this hairy covering is found on a very great number of 

 tropical animals ; secondly, it has in this instance struck us so much, be- 

 cause it occurred in an animal that we are accustomed to see without any 



