PRONOMOTHERIUM 



163 



directly forward. The posterior portion of p 1 is sharp (chisel-like), and slightly concave on the inner surface. 

 The anterior ridge on p" is inflected forward in such a way that the outer surface is concave and the inner one 

 convex. The posterior cingular festoon is much larger than the anterior one. A portion of it is developed into 

 a small subcorneal cusp which represents the deuterocone. The outer face of the tooth is slightly concave antero- 

 posterior^ and convex vertically. P 3 is wider than p 2 , especially the anterior portion. The deuterocone does 

 not appear to be much larger. P 4 has a strong inner cingulum. The inner crescent is concave vertically. 



Fig. 115. — Pronomotherium altiramus (Douglass). Flesh restoration of head by Prof. R. S. Lull. 



from Douglass. 1/5 nat. size. (After Thorpe, 1925.) 



Skull and jaw modified 



Inferior teeth: There is no trace of Ii, and the inner border of the alveolus of 1 2 is only about 

 1.5 mm. from the edge of the symphysis. The canine alveolus is triangular, with the posterior side 

 the broadest. This tooth was much smaller than the caniniform Pj. The latter is set diagonally in 

 the jaw and is nearly lenticular in cross section. The anterior and posterior edges were sharp, and 

 the tooth apparently terminated in a sharp point. P 2 is thin, compressed, and trenchant, and is set 

 diagonally in the ramus. 



Fig. 116. — Pronomotherhun altiramus (Douglass). Crown view of inferior dentition. 



Nat. size. (Redrawn from Douglass, 1907.) 



HT. Cat. No. 759 CM. 



First in describing P 2 , then in comparison with P 3 and P 4 , Douglass says (1901 A, pp. 73-74): 



The highest point and the convexity that descends from it are in the median line, but the posterior slope is 

 steeper and longer. As seen from above the crest is sigmoid. In front of the highest point there is a hint of the 

 anterior inner lobe that is quite prominent in pms 3 and 4. Back of this is a small groove. On the posterior inner 

 side of the tooth is a slight concavity, and another faint depression on the posterior outer surface. On the 

 posterior margin the descending ridge divides, forming a little delta. In the third premolar these points are all 

 more prominent and the posterior internal concavity has become quite a deep fossa bounded anteriorly by a promi- 



