JR. S. Lull — Evolution of the Elephant. 197 



the latter and E. invperator. In fact, they greatly resemble 

 those of the modern Indian elephant. E. columbi was early 

 and middle Pleistocene in distribution, more southern in range 

 than E. primigenius, though the two inhabited a broad fron- 

 tier belt along the northern United States. E. columbi reaches 

 the maximum of evolution in the shortening and heightening 

 of the skull. The tusks in a mounted specimen in the American 

 Museum of Natural History are so huge that their tips actually 

 curve backward and cross each other. They have completely 

 lost their original digging function and their use as weapons 

 must have been much impaired. They seem to represent an 

 instance of a certain acquired momentum of evolution carrying 

 them past the stage of greatest usefulness to become an actual 

 detriment to their owner. This may have been an important 

 factor for extinction. Specimens at Yale referable to E. col- 

 umbi consist of several molars from Idaho, Florida, California, 

 and Mexico. 



JElephqs primigenius. 



The mammoth was not among the largest of elephants, being 

 but little in excess of Elephas indicus in height, but with 



Fig. 25. Tooth of E. primigenius ( x ^) ; after Marsh. 



relatively huge tusks exceeding, in some instances, a length of 

 over eleven feet measured along the outer curve. The teeth 

 have the most numerous and finest lamellae, and in this respect, 

 as well as in the development of hair, this creature shows the 

 greatest degree of specialization as compared with the tusks and 

 skull in the Columbian species. It is curious to note, however, 

 that in three ways one can trace the increasing fineness in the 

 lamellae of the molars corresponding to the three modes of dis- 

 tribution, — latitude, altitude, and time, — for the more ancient 

 individuals, living the farthest south and nearest the sea-level, 

 have teeth very much like those of E. columbi. The increasing 

 fineness of lamellae is correlated with increasing cold and a conse- 

 quent change in the character of food plants, as the last of the 



