44 



DINOCERATA. 



young, these tusks grow from a persistent pulp, but in old age the cavity 

 becomes neai-ly closed. In the male, these tusks are large and powerful, 

 and extend downward nearly or quite to the extremity of the pendent 

 process of the lower jaw . 



Figure 49. — Upper cauiue of Tinoceras ijraiule, Marsh (Xo. lOiO); male. 

 Figure 50. — Upper camne of Dinoreras latirejis, Marsh (No. 1222); male. 



a. lateral view showiag outer surface; h. inner surface; I', b". sections; r. front view. 



The dotted line on the teeth marks the position of the alveolar border, below which the tusk 

 was exposed. 



All the figures are one-fourth natural size. 



In Dinoceras mirahile (number 1036), the canine tusks are oval 

 in section, where they emerge from the jaw, then become somewhat 

 constricted, before expanding into a wide, thin, Ltnceolate extremity, as 

 shown in Plate I. On the outer surface of these tusks, there is a distinct 

 ridge in tlie lower half exposed, giving there a subtriangular, or bayonet- 

 like form. 



