OREODONTOIDES 213 



Dentition: This species is approximately the size of Merychyus elegans, and a comparison of 

 the teeth is made with that species. From the alveoli it appears that the incisors and canines were 

 about the same size in each species. P, is smaller than the comparable tooth in M. elegans and is 

 also smaller than P 2 in M. relictus. It likewise differs in that its crown is premolariform, with a 

 compressed pointed apex, and with the anterior edge inwardly recurved. It is set obliquely in the 

 jaw. P-, likewise set obliquely, is much larger than in M. elegans, and the inner crescents are rudi- 

 mentary. The posterior basin of P 3 is divided by a posterior intermediate crest. This condition in 

 M. elegans is very rudimentary. The posterior part of P 4 is decidedly small, and the anterointernal 

 pillar has enlarged very markedly over the condition in Ticholeftus. This cusp-like pillar is absent 

 in M. elegans. The metastylid of M 3 , composed of two distinct crescents later united by wear, is 

 nearly in the same line as the two anterior crescents at the base of the crown. In an unworn condi- 

 tion the metastylid appears to turn outward to an angle of about 25° from that line. All the teeth 

 have approximately the same degree of hypsodonty as in M . elegans. 



Discussion: Matthew and Cook (1909, p. 393) mentioned a large variety of this species or 

 thought possibly it might be a distinct species, based on parts of upper and lower jaws. They stated 

 that the specimens were slightly larger throughout than M. elegans and about intermediate in size 

 between that species and Merychyus medius (now Metoreodon ? medius). I should refer them to 

 M. relictus, for it seems to me that the type may represent a female and these larger specimens the 

 male. The type has a relatively slender ramus and appears to be more or less delicate in build when 

 compared with the average of the different species. 



The geologic horizon of the type of M. relictus is doubtful, but Matthew thought it was prob- 

 ably lower Snake Creek, for in 1924 he had specimens apparently belonging to this species from 

 that horizon. 



MERYCHYUS STOCK 



Genus OREODONTOIDES Thorpe 1921 



Table 12 



Original Reference: See under O. oregonensis Thorpe. 

 Genotype and only Species: Oreodontoides oregonensis Thorpe. 

 Genoholotype: Cat. No. 12329 Y.P.M., skull, moderately well preserved. 



Distinguishing Characters: Size small; skull mesocephalic tending toward brachycephalic; 

 diameter of postorbital constriction and of brain case unusually large; nasal bones reduced; skull 

 depressed fore and aft; orbits large; malar shallow; sagittal crest lacking; lacrimal fossa deep; 

 dentition brachyodont, with premolar length nearly as great as that of molar (index 0.95); styles 

 vertical and of uniform width from top to bottom. 



Etymology: Oreodontoides (Oreodon + like). 



Oreodontoides oregonensis Thorpe 1921 

 Figs. 155-159 



Original Reference: John Day eporeodons. Amer. Jour. Sci. (5), II, pp. 107-109, figs. 11-13. 



Type Locality: Turtle Cove, John Day Valley, Oregon. 



Geologic Horizon: Lower Miocene (upper John Day). 



Types: Genoholotype, Cat. No. 12329 Y.P.M., skull, of which zygomata are incomplete, basicranial region 

 is considerably damaged, and crowns of some teeth are missing and of some others are more or less damaged. 

 Plesiotypes, Cat. Nos. 12635 and 12638 Y.P.M., anterior parts of two sets of rami united at symphysis and 

 having teeth, except that molars are incomplete. 



