TJINTATHERIID^:. 



179 



Section DINOCERATA. 



The superior incisors are absent, and there is no third trochanter 

 to the femur. The cranium carries several pairs of large protu- 

 berances ; the upper canines of the males are of large size, and are 

 frequently protected by a descending mandibular flange l . 



Family UINTATHEBIID^. 



This is the only family at present known. The hinder upper 

 premolars are as complex as the true molars (woodcut, fig. 28), and 



Fig. 28. 



pnt. 



Tinoceras stenops, Marsh. The left upper and lower cheek-dentition ; from 

 the Eocene of North America. J. (From Marsh's ' Monograph of the 

 Dinocerata.') 



there is no distinct third lobe to m . 3 ; in the last five upper cheek- 

 teeth the two transverse ridges unite on the inner border of the 

 crown to form a single V; a very similar V, with the angle directed 

 inwards, occurring in the corresponding lower teeth. According to 

 Marsh 2 there are always three lower incisors, but Cope states 3 that in 

 some members of the type genus Uintatherium (in which Cope in- 

 cludes Dinoceras) they are reduced to two or even one. In the 

 present Catalogue the generic divisions adopted by Marsh are pro- 

 visionally accepted, although it seems very doubtful whether their 

 differences are more important than those between the different 

 groups of the genus llhinoceros. 



1 For other characters see Marsh . ' Monograph of the Dinocerata ' (U. S. 

 G-eol. Surv. vol. x. [1884]). 2 Op. cit. pp. 41, 191. 



3 Araer. Nat, vol. xix. pp. 44, 53 (1885). 



