R. S. Lull — Evolution of the Elephant. 



191 



served part of the holotype of Tetrabelodon shepardi Leidy 

 from California, of which the remainder is in the museum of 

 Amherst College. 



Dibelodon, 



The genus Dibelodon is known principally from the jaws, 

 teeth and tusks, though two splended skulls of D. andium are 

 preserved in the Museo Nacional in Buenos Aires. The upper 



Fig. 18. Skull of Dibelodon andium. 



tusks are well developed, displaying an elongated spiral form, 

 with a well developed enamel band, but the lower jaw is quite 

 short though the symphysis is longer and more trough-like 

 than in the genera Mammut and Elephas. The lower tusks 

 have entirely disappeared and with the shortening of the jaw 

 the trunk must have become pendant as in the modern 

 elephants. 



The genus Dibelodon contains several species, among which 

 are Dibelodon humboldii (Cuvier), D. mirificium (Leidy), 

 D. prceeursor (Cope), and D. andium (Cuvier). Of these 

 Dibelodon humboldii and D. andium- ranged into South 

 America and were in fact almost the only proboscidians to 

 cross into the southern hemisphere of the ISFew World. Some 

 of these animals lived in the high Andes at an elevation of 

 12,350 feet above the level of the sea, at a time when the 

 region had a greater rainfall than now and therefore a richer 

 vegetation. 



The Yale collection contains teeth and portions of the tusks 

 of Dibelodon mirificus and D. obscurum as well as Of D. 

 humboldii. One D. -obscurum specimen is part of that 

 figured by Leidy, the remainder being in the Amherst College 

 Museum. There are also preserved at Yale a femur and an 

 axis probably referable to Dibelodon andium, from the Plio- 

 cene Bone Bed of Quito valley, South America, found at an 

 altitude of 10,000 feet. 



