PLEISTOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 441 



overlapping in time and in range, will probably be found to be characteristic 

 of distinct epochs and habitats, as follows: 



3. The northern mammoth {Elephas primigenius) , ranging from Alaska 

 south to the latitude of Washington. Late Pleistocene, or Zone III. 



2. The Columbian mammoth (Elephas columbi), ranging from the 

 southerly range of E. primigenius to the City of Mexico. Mid-Pleistocene, 

 or Zone II. 



1. The imperial mammoth (Elephas imperator), ranging from Nebraska 

 to the City of Mexico. Early Pleistocene, or Zone I and (?) II. 



Fig. 191. — Middle Miocene mastodon {Trilophodon productus) beside Upper Pliocene or 

 Lower Pleistocene elephant {E. imperator). Models by Charles R. Knight in the American 

 Museum of Natural History. 



The imperial elephant is an early arrival. It is by far the largest of 

 these animals, attaining a height of over thirteen feet, and more definitely 

 distinguished by the enormous size of its molar teeth, in which the enamel 

 plates are relatively iew (seventeen), widely separated, and surrounded by a 

 heavy mass of cement. 



The Columbian elephant is an animal of lesser size, attaining a height 

 of eleven feet, with twenty-one to twenty-two cross ridges in its upper 

 grinders. 



