38 



DINOCEHATA. 



Tliat tlie same relation in size between tlie tusk and process below 

 it holds equally in both the genera Dmocerns and T'moceras, is 

 conclusively shown by various specimens in the Yale ]\Iuseum. 



Figure 39. — Lower jaw of Dinoceras mirahile. Marsh (No. 1251); seen from the left. 

 Figure 40. — The same jaw; seen from the front. 



c. alveole of <';miMe; /. anterior foramen; di. deeidnous incisor; i. alveole of incisor; in. mental 



foramen; ;). process for protection of tnsk. 



Both fior\ires are one-fourth natural size. 



In the genus Dinoceras, there are three incisor teeth, and a small 

 incisiform canine on each side forming a continuous series at the front 

 extremity of the lower jaw. These are all of moderate size, and inclined 

 well forward, as in the ruminant mammals. Behind this series, and 

 immediately over the dependent process, is a long diastema (Plate VIII, 

 figure 1, d). Furtlier back, there are tliree j)remolars, and three 

 molars, forming together a close series. This is the dentition, essentially, 

 in the lower jaw of both Dinoceras and Tinoceras, and will be described 

 more fully in the following eliapter. 



In a lower jaw found near the locality of tlie type of Uintatheriwn 

 rohustum, and here referred to that genus, there are four premolars instead 

 of three. The first pj-emolar, wanting in Dinoceras and Tinoceras, is of 

 small size, and is ])laced just liehind the lower canine. It is separated 

 from the second premolar by a diastema, as shown in figures 41 and 42, 

 page 39. 



