THE TEETH. 



43 



continue the deep groove on the upper part of the lower jaw, above the 

 synaphysis. The position of the sockets for these teetli in Bhioceras is 

 shown in Phites XII and XIII, and tlie form of tlie teeth, in Plate VIII, 

 figure 1. The crowns of these incisors are covered with enamel, and the 

 special features of both crown and root are shown in figures 43-45, page 42. 

 In the genus Tinoceras, the incisors are similar in form, but have a 

 less inclined position, as indicated in Plnte XIX, figure 1. 



FicnuE 4ii. — Uiipor canine of Duiuceras lucare, Marsh (No. 10.^8): male. h. lateral vievr, inner surftice; 



b'. outline of section of tooth ; b". section of tooth showing: pulp cavity ; c. front view of lootli. 

 FiQURB 47. — Upper canine oi THnoceras laticeps, Marsh (No. 1202); female, a. outer surface; h. inner 



surface; b'. outline of see ion ; c. front view. 

 Figure 48. — Upper canine of Tiitorenis hmgiceps, Marsh (No. 125G); female, a. outer surface; 1i. inner 

 surfiiee ; c. front view of tooth. 



The dotted line on tlie teeih marks the position of the alveolar iiorder, below wliicli the tusk 

 was exposed. 



All the figures are one-fourth natural size. 



The Canines. 

 The superior canines of Dhtnceras are long, recurved, trencliant tusks. 

 The crown is covered with enamel, and the root extends upward into the 

 base of the maxillary ^^I'otuberance, or horn-core. When the animal is 



