CENOZOIC ERA: AGE OF MAMMALS 615 



have accumulated in the depressions of the latest glacial deposits. 

 Paintings and carvings on ivory of mammoths, made by prehistoric 

 man in Europe, prove the existence of elephants after the appearance 

 of man on that continent. There is, however, no evidence pointing 

 to their presence in North America since the advent of man. 



Summary of the Evolution of the Elephant. — (1) The few (three 

 in each half jaw) long, large, many-ridged teeth of the elephant, of 

 which not more than one and one 

 half are in use in each half jaw at 

 one time, were developed from 

 small, short-crowned, simple teeth 

 with two poorly developed ridges. 

 (2) The tusks are greatly elongated 

 front teeth (incisors). (3) The 

 trunk began as a short, flexible lip 

 which, as the lower tusks became 



longer, gradually lengthened to Fig. 549. — Restoration of a Miocene 



Wi i i 1 elephant (Dinotherium) with tusks on 



e the animal to reach the the lower jaw . (After H. F. Osborn.) 

 ground for food (Fig. 549). The 



trunk at first rested upon the lower tusks, but when these disap- 

 peared in the course of the evolution of the race, it hung straight 

 down and because of this new position soon developed its present 

 characteristics. (4) Accompanying the development of the trunk 

 and tusks was a shortening of the neck. (5) The bulk and height of 

 the animal increased and the leg straightened to support the greater 

 weight. 



REFERENCES FOR ELEPHANTS 



Hutchinson, H. N., — Extinct Monsters and Creatures of Other Days, pp. 249-282. 

 Lankester, E. R., — Extinct Animals, pp. 125-132. 



Lull, R. S., — The Evolution of the Elephant: Am. Jour. Sci., Vol. 25, 1908, pp. 169-212. 

 Scott, W. B., — A History of Land Mammals in the Western Hemisphere, pp. 129-199; 

 422-442. 



Even-toed Hoofed Mammals (Artiodactyls) 



This division of the hoofed mammals (Fig. 540, p. 599) is the most 

 important at present, being represented by such animals as the camel, 

 deer, sheep, goat, and antelope. 



Camels. — Evidence that the climate over large areas of the 

 western interior of North America was dry for long periods of time 

 is shown, as has been indicated (p 611), in the evolution of certain 



