THE TEETH. 51 



The corresponding teeth in the genus Tinoceras are well shown in 

 Plate XIX. The posterior transverse crest of the penultimate and last 

 lower molar have here a distinct tubercle at their inner extremity, at the 

 apex of the typical V-shaped pattern. This is shown especially in figure 

 2 of Plate XIX. In figure 54, on page 47, the lower molar series of 

 Tinoceras stenops is represented. 



All of the incisors, canines, and premolars in Dinoceras and Tinoceras 

 appear to have been preceded by a series of temporary teeth. The 

 incisors, and lower canines sometimes made their appearance before 

 their small predecessors had disappeared. In one specimen, I'epresented 

 in figures 39 and 40, page 38, these immature teeth are seen in place in 

 small cavities in the sides of the alveoles of the permanent dentition. 



The lower incisors and their accompanying canines ai-e usually more 

 or less worn. This is due mainly to the food consumed, and in part to the 

 attrition of the upper canines, and, perhaps, also to a heavy, coarse, upj^er 

 liji. The premaxillaries, being edentulous, probably supported a pad, as 

 in ruminants. 



The ujjper canines show distinct ti-aces of wear on their inner surface 

 near the base, and, also below, near the aj^ex of the crown. This wear is 

 jjrobably due to the action of the agencies just described. 



A more difficult problem is presented by the worn surface 

 sometimes seen on the outer face of these tusks, somewhat below the 

 insertion in the jaw, as shown in figure 51, page 45. This is probably 

 due to the wearing action of a heavy upper lip. 



The molar teeth in Dinocerata appear to resemble more closely the 

 corresjionding teetli in the genus Coryphodon than those of any other 

 animal. The general dentition, however, is quite distinct. Cury])lioclon 

 has Avell developed upper incisors, and a medium-sized upper canine, thus 

 differing widely in these features from the Dinocerata. The jiosition and 

 size of these tpeth in Coryphodon are shown in figure 66, page 63. The 

 upper and lower molar se_ries are shown in figures 55 and 56, page 52. 



