14 



flie life that preceded the change as a tapir or civet-like carnivore is of the age 

 that followed. 



It has been stated that the life of the present period in the southern 

 hemisphere is not homogeneous. The same is true though in a less degree 

 of the northern. Thus, if we include India in the latter, the elephant is a 

 Pliocene form, and the true rhinoceros Upper Miocene. In the northern 

 hemisphere, the dogs are Miocene. In North America, the opossum, and 

 probably the raccoon, are Eocene; the wolves and foxes are Miocene, and the 

 weasels Pliocene. Perhaps, the cats first appeared in our Pliocene. Com- 

 paratively few mammalian types mark, by their origin, the latest geologic 

 epochs. Such are the ruminants, as deer, and oxen, with the true horses, 

 which all commence in the Upper Pliocene of Arctogaea. Finally, man alone 

 signalizes the last or glacial period, and is to reach his culmination in the 

 ages that intervene between that great time-boundary and one to come. 



Thus, a certain proportion only of the life of a given epoch is character- 

 istic of it, that is, originates in it; the remaining members being legacies from 

 preceding ages. Hence, the latest forms of life embraced in an extinct fauna 

 are the true indicators of the chronological relations of that fauna. 



