634 UNGULATES. 



one inch to one inch three lines. There are two roots, the cavity 

 of the small anterior one expands in the crown, and is continued 

 into that of the three anterior plates. The thicker root supports 

 the rest of the tooth. The second molar is worn out and shed, 

 before the beginning of the sixth year. 



The third molar has the crown divided into from eleven to 

 thirteen plates ; it averages four inches in length, and two inches 

 in breadth, and has a small anterior, and a very large posterior 

 root ; it begins to appear above the gum about the end of the second 

 year, is in its most complete state and extensive use during the 

 fifth year, and is worn out and shed in the ninth year. The last 

 remnant of the third molar is shown at m 3, fig. 1. It is probable 

 that the three preceding teeth are analogous to the true deciduous 

 molars of ordinary Pachyderms . 



The fourth molar presents, as M. de Blainville well observes, 

 a marked superiority of size over the third, and a somewhat 

 different form : the anterior angle is more obliquely abraded, giving 

 a pentagonal figure to the tooth in the upper jaw (ib. fig. 1 m 4). 

 The number of plates in the crown of this tooth is fifteen or 

 sixteen : its length between seven and eight inches ; its breadth 

 three inches. It has an anterior simple and slender root sup- 

 porting the first three plates ; a second of larger size and bifid, 

 supporting the next four plates ; and a large contracting base for 

 the remainder. The fore part of the grinding surface of this tooth 

 begins to protrude through the gum at the sixth year : the tooth 

 is worn away and its last remnant shed about the twentieth or 

 twenty-fifth year. It may be regarded as the analogue of the first 

 true molar of ordinary Pachyderms. 



The fifth molar with a crown of from seventeen to twenty 

 plates, measures between nine and ten inches in length and 

 about three inches and a half in breadth. The second root is 

 more distinctly separated from the first simple root than from 

 the large mass behind. It begins to appear above the gum 

 about the twentieth year : its duration has not been ascertained 

 by observation ; but it probably is not shed before the sixtieth year. 



