METOREODON 



205 



vex, that is, it has begun to assume the premolar i form shape. In cross section the anterior side is 

 nearly semicircular, while posteriorly it is much less convex. P. is placed at an angle of approxi- 

 mately 45° with the line of the ramus. Its greatest diameter is 16 mm., but the anteroposterior 

 space it occupies is but 8 mm. In P 2 the anterior lobe has been twisted inward and backward. P 3 is 

 set somewhat obliquely. In P 4 the posterior portion is small, and the fold of enamel between the 

 posterior lobes hasby wear become an enamel lake. In P 3 the anterointernal crest turns backward, 

 and in P 4 this has increased partially to enclose the anterior basin. 



The molars are so worn that details are obscured, except for the outline, but apparently they 

 conform to the Metoreodon pattern. 



Discussion: I have no hesitancy in referring this species to Metoreodon, although the material 

 upon which to base conclusions is very limited. In general, the mandibular form corresponds to 

 that of M. profectus; the length of the premolar series is the same in both, as are also the dimensions 



Fig. 148. — Metoreodon compressidens (Douglass). Fragmentary mandible and dentition. HT. Cat. No. 801 CM. 



1/2 nat. size. (After Douglass, 1901.) 



of Mj and M> Pi has the same length but is slightly wider in M. compressidens ; P 2 is slightly 

 longer but of the same width; P 3 has the same proportions but is slightly smaller; and P 4 , judg- 

 ing from the alveolus of the type in M. frofectus, is approximately the same in size and proportions. 

 M. compressidens is very close to M. profectus, but the development of the premolar pattern is 

 less advanced. It is intermediate in this character between M. relictus and M. projectus. Again, 

 the latter two species were collected in Nebraska and are probably lower Pliocene in age, while 

 M. compressidens came from Montana and was in the Madison Valley beds, ascribed to the upper 

 Miocene. 



Metoreodon major (Leidy) 1858 

 PI. XXXVII, figs. 12-13 



Original Reference: Notice of remains of extinct Vertebrata, from the valley of the Niobrara River. 

 Proc. Acad. Nat. Sci. Phila., X, p. 26 (Merychyus major). 



Type Locality: Probably from the headwaters of the Niobrara River, and certainly between the mouth 

 of the Turtle River and a point 300 miles upstream, in Nebraska. 



Geologic Horizon: Upper Miocene (Bed F of Hayden). 



Type: Holotype, Cat. No. 439 U.S.N.M., part of right upper jaw containing P 3 , P 4 , M 1 , and M 2 . 



Specific Characters: This species and M. calif ornicus are the largest forms in the genus as 

 now known. Unfortunately no complete skull or jaws have been described, so that we have to 

 depend upon the limited dentition of the type for specific distinctions. The mandible is shallower 

 and more slender than that of Merycochoerus proprius. 



