190 



JR. S. Lull — Evolution of the Elephant. 



rior tusks finally disappear. The upper tusks in Tetrabelodon 

 were longer than those of the lower jaw but did not extend 

 much beyond the latter. The tusks had an enamel band upon 

 the outer and lower face and were slightly curved downward. 

 The nasal orifice had receded farther to the rear, indicating a 

 still greater development of the trunk than in Palceomastodon. 



Fig. 16. Skull of Tetrabelodon angustidens. 



The proboscis, still supported from beneath by the rigid lower 

 jaws, could only be raised and moved from side to side. The 

 neck is now quite short, so much so that were it not for the 



proboscis and tusks this creature 

 * could not reach the ground. Both 

 upper and lower tusks show signs 

 of wear which could only be caused 

 by digging, those on one side being 

 often much more worn than on 

 the other. 

 Fig. 17. Tooth of Tetrabelodon The teeth have increased in size 



anqustidens xl), i , -i , •■ 



to such an extent that but two 

 adult grinders at a time can be contained in each half of the 

 jaws. 



Tetrabelodon was a widely spread, migratory form, for we 

 find species referable to this genus not only in Europe but in 

 Africa, Asia, and in Worth America. In Eurasia it gave rise 

 to Mammut through the loss of the lower tusks and the 

 enamel band, while in America there arose Dibelodon, which 

 retained the enamel band and which was the first proboscidian 

 to reach South America after the formation of the Central 

 American land connection either late in the Miocene or in the 

 early Pliocene. 



The Yale Museum contains fine specimens of teeth and 

 tusks of Tetrabelodon angustidens from France as well as 

 similar remains of Tetrabelodon poavus, T. ca?npestw, T. 

 productus, and T. serridens. In the Yale Museum is also pre- 



