HISTORY OF THE fAMBLYPODA 



445 



the ftitanotheres and tentelodonts, this deficiency of brain-de- 

 velopment was at least one of the factors which led to the early 

 extinction of the group. The premaxillaries were slender and 

 rod-like bones, which did not meet in the middle line and carried 

 no teeth. The long and massive nasal bones and the position of 

 the nasal opening show that these animals cannot have had 

 a proboscis of any kind. The lower jaw was remarkable for 

 the great bony flange which, in the males, descended on each 



Fig. 230. — Skull of tuintathore (t Uintatherium alticcps) , lower jaw supplied from another 

 species. Princeton University Museimi. For re.storation, see Fig. 231, p. 447. 



side from the lower border, near the anterior end, and served 

 to protect the great canine tusks from fracture. 



The female skull differed in two respects from that of the 

 male : (1) the horn-like protuberances were much more slen- 

 der and less prominent ; (2) as the upper canine did not form 

 a tusk, the lower jaw had no flanges. The skull of the artio- 

 dactyl fProtoceras (p. 406) was remarkably similar to that of 

 the tuintatheres. 



The dental formula was: 1 1, c-];, 7?|, mf, X 2 = 34. The 

 upper incisors were completely lost and the lower ones had the 



