208 



THE MERYCOIDODONTIMi 



Mandible: This is of nearly uniform depth below the tooth row, and the inferior border is 

 almost straight, except for a shallow descent at the angle. The masseteric fossa is small but deep, 

 the condyle is gently convex, the sigmoid notch is small and shallow, and the coronoid process is 

 low and curved backward. 



Fig. 150. — Metoreodon novomexicanus (Frick). Mandible. CT. Cat. No. 32051. A.M.N.H. 2/3 nat. size. 



Dentition: Compared with M. major, the superior teeth are more advanced. P 3 is shorter 

 and much wider, P 4 is shorter and about the same in width, M l is shorter and wider, while M 2 is 

 somewhat shorter and almost as wide. All the teeth are heavier. The internal cingulum on P 4 is 

 not so heavy. In P 3 the posterior crescent closes the posterior basin more completely, the antero- 

 internal tubercle is larger and is joined to the median crest, filling more of the anterior basin, while 

 the anterointernal cingulum has greatly strengthened and enlarged. 



Fig. 151. — Metoreodon novomexicanus (Frick). 



Superior view of mandible. CT. 

 2/3 nat. size. 



Cat. No. 32051 A.M.N.H. 



Compared with M. frofectus this species is considerably more advanced, as well as larger, but 

 the molar-premolar index, 0.66, is the same for both. I 1, 2 are of about equal size, and the width 

 of the crown of I 3 is more than twice that of I 2 , while in M. frofectus I 1, 2 are also of nearly equal 

 size but are relatively larger, and I 3 is less than one and a half times as wide as I 2 . The antero- 

 internal cusp and cingulum are relatively much larger and more prominent on each of the three 

 anterior premolars, and the median crest joins the tubercle, which it does not do in either M. frofectus 

 or M. major. M 2 is nearly square in M. novomexicanus but in M. frofectus is considerably nar- 

 rower, although of the same length, while M 3 of M. novomexicanus is considerably longer than 

 wide in proportion to that tooth of M. frofectus. 



