l'ROTOREODON 39 



Foramina: The infraorbital foramina are above the posterior part of P 3 . The supraorbitals 

 are 1 2 mm. apart. The foramen ovale and the foramen rotundum are both large, and the posterior 

 palatine foramina are opposite the interval between P 3 and P 4 . 



Dentition: Superior: The hypocones are but little smaller than the protocones. There are 

 strong internal cingula on the protocones and on P 4 , but those on the hypocones are very faint. 

 The styles are stout and rounded. The fifth cusp (or protoconule) is small but distinct. P' has an 

 incipient conule arising from the posteromedian part of the cingulum. P 3 is triangular in outline 

 with the apex internal. The posterior crescent is much larger than the anterior. The anterior and 

 posterior crests are well developed, but the median one is very weak. The two anterointermediate 

 crests, shown in P. melius, are here reduced to the merest of tiny ridges. There is no posterointer- 

 mediate crest. P" is small and compressed, as is also P 1 , which is isolated. The canine is sub- 

 circular, with a posterior transverse plane surface. The three incisors are like tiny round pegs, very 

 slightly spaced. 



Inferior: The metastylid of M :! is very large and robust. P 4 has well-marked anterior, pos- 

 terior, and median crests well developed, together with anterior and posterior crescents. This tooth 

 is very similar to the corresponding tooth in Merycoidodon, except that the posterior crescent is not 

 completely closed in this Uinta form. P 2 and P s also have the three main crests well developed. 

 Pi is large and lenticular in section. The true canine is nearly circular in section, whereas the three 

 small incisors are very narrow transversely and are closely pressed one against the other, and the 

 third against the canine. The superior molar-premolar index is 1.09 and that of the lower series 

 1.05. 



Skeleton: The radius and ulna, as well as the tibia and fibula, are separate. The former 

 two are nearly equal in size, and the fibula, though slender, is complete. There were four func- 

 tional digits in both manus and pes, and also the remnants of a fifth (actually the first) in each. 

 The digits possessed narrow hoofs, more like those of the merycoidodonts than like the claws of 

 A griochoerus . The navicular and cuboid are distinct. 



Discussion: A left M 2 , collected in upper Eocene strata, 11 miles southeast of Swift Current, 

 Saskatchewan, Canada, was described by Russell and Wickenden (1933, pp. 63-64) and provision- 

 ally referred by them to P. parvus. It is larger than the corresponding tooth in that species but is 

 of almost exactly the same dimensions as that in P. pumilus. It differs from both species in the 

 following characters. It lacks the internal cingulum, the hypocone is reduced, and it possesses a 

 small spur, directed outward from the posterior wall of the protocone. This last structure I have 

 not seen in any specimen of the oreodonts. In this feature alone it resembles Protylopus annectens. 

 It is much nearer to Protoreodon than to Protagriochoerus, and I should refer it provisionally to 

 P. pumilus until we have more material of this very interesting specimen. 



Protoreodon species Peterson 1931 



Original Reference: New species from the Oligocene of the Uinta. Ann. Carnegie Mus., XXI, p. 75, 



fig. 11. 



Locality: Three miles north of Leota Ranch and one mile west of Green River, Uinta County, Utah. 

 Geologic Horizon: Upper Eocene-lower Oligocene (hasal Duchesne River). 

 Material: Cat. No. 1 1 864 CM., a few fragments of a skeleton. 



Discussion: Peterson provisionally placed this specimen with Protoreodon. It is very nearly 

 the size of Merycoidodon culbertsonii, and his description is as follows: 



The astragalus of the specimen from Utah is wider than in Protoreodon ?nedlus, but not as broad as in 

 Merycoidodon. Likewise the cuboid is relatively lower than in the latter genus. Altogether the new material, 

 which is too incomplete to be made a type, apparently represents an intermediate form between Protoreodon and 

 Merycoidodon. 



