336 



THE AGE OF MAMMALS 



Upper Pliocene Etruscan type of Europe. The ruminants include buffaloes, 

 nilgais, gazelles, black bucks, antelopes resembling the oryx, four-horned 

 antelopes, sambar and axis deer, muntjacs, chevrotains, the wild boar, 

 and wild pigs. With the upper layers of animal remains traces of man are 

 found, and even at the lower levels are found primitive implements. 



III. PLIOCENE LIFE OF NORTH AMERICA 



The close of the Miocene and opening of the Pliocene cannot be dated 

 in the western plains region of North America as in Europe, because while 

 in Europe there is a marked interruption in the conditions of life at the 

 close of the Miocene, in the western plains and mountain regions of North 



Fig. 156. — Upper Miocene and Pliocene distribution of the Strepsicerine and Hippotragine 

 Antelopes. Known distribution in black, hypothetical migration area in oblique lines. 



America both the conditions of life and the mammalian fauna continue 

 without a break. This, like the American passage from the Oligocene to 

 the Miocene and that from the Miocene to the Pliocene, is an artificial one, 

 made for purposes of convenience and of correlation with the Old World 

 time scale. 



As regards the time scale, a new feature of paramount importance and 

 interest arises in connection with the sudden and welcome extension of our 

 knowledge of the mammals of North America to the far southeast, along the 

 ancient seacoast of Florida. Here appear for the first time in North America 

 means of correlation such as characterize European formations through- 

 out, namely, the alternation of marine shel 1-b earing forma- 

 tions with freshwater mammal-bearing formations. The 

 former contain invertebrates which may be closely compared with those of 



