UINTATHERIID.E. 



179 



Section DINOCEEATA. 

 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 \ 



Family UINTATHEKIID.E. 



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. 



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

 the Eocene of North America, f . (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 Y, 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 Rhinoceros. 



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

 Geol. Surv. vol. x. [1884]). 2 Op. tit. pp. 41, 191. 



3 Amer. Nat. vol. six. pp. t4, 53 (1885). 



