HYOMliRYX, BATHYGENYS 41 



In crown pattern the premolars and molars of the superior series are much like the Protoreodon 

 pattern. They differ from P. fumilus in lacking internal cingula, in having less prominent styles on 

 the molars, and in that the outer faces of the crescents are flatter and more nearly vertical. The 

 inferior series shows the full dentition, with Pi caniniform. The premolars and incisors are 

 crowded but do not overlap. 



Marsh believed that this form was close to P. fumilus, except for the reduction of the 

 premaxillaries and the lack of incisors. 



I consider it an aberrant branch of the merycoidodont stem, probably not arising directly from 

 Protoreodon, as the two genera are contemporaneous. 



At present the generic and specific characters cannot be separated. 



Etymology: Hyomeryx (hog + ruminant = ruminating hog). 



Genus BATHYGENYS Douglass 1901 

 Table 1 



Bathygenys alpha Douglass 1901 

 Figs. 18-20 



Original Reference: Fossil Mammalia of the White River beds of Montana. Trans. Amer. Philos. 

 Soc. (2), XX, pp. 256-259, pi. IX, figs. 7-8. 



Type Locality: Pipestone Springs, Jefferson County, Montana. 



Geologic Horizon: Lower Oligocene (Pipestone). 



Types: Genoholotype, Cat. No. 708 CM., anterior portion of left ramus, with part of canine alveolus, 

 root of P„ alveolus of P 2 , and P 3 and P 4 complete. Paratype, Cat. No. 708A CM., part of right ramus with 

 last three premolars and first molar. Plesiotypes, Cat. No. 9671 A.M.N.H., fragment of maxillary with 

 molars and last premolar complete, and Cat. No. 9673 A.M.N.H., part of right ramus with P 4 to M 2 . 



Description: The original types are parts of rami, and the skull structure is unknown. 



Mandible: The profile of the chin, so far as shown, is straight, and the symphysis is steep, with 

 a transverse convexity. The symphysis is broader below, and the posterior part lies beneath the 

 posterior of P 4 . The horizontal ramus gradually deepens as it approaches the ascending ramus. 



Dentition: The teeth are all brachyodont. Superior: P 4 has no internal cingulum, except a 

 short posterointernal one, and lacks the anteroexternal ridge. The molars have no trace of a 

 protoconule, and the protocones of M 1 and M 2 are considerably wider than the hypocones, while 

 those of M 3 are more nearly the same in width. The molars and P 4 are all wider than long. The 

 posterior half of M 3 in proportion to the anterior part is similar to that of Agriochaerus and 

 Protoreodon, instead of the hypocone being less in width than the protocone, as it is in most of the 

 merycoidodonts of the Oligocene and above. The parastyles and mesostyles are moderately promi- 

 nent and are strongly offset from the next tooth. The faces of the paracones and metacones are 

 nearly flat. The metastyle of M 3 is very poorly developed. 



Inferior: The molars are nearly of the proportion of those in Merycoidodon, although the 

 protoconid of Mi is noticeably smaller than the hypoconid. The last two premolars are longer than 

 wide, with a large posterior basin, and the anterior, posterior, and median crests are well devel- 

 oped, while the anterior crescent is feebly developed. Douglass compared them with his Meryco- 

 chaerus ? specimens from Montana, which are now referred to Pronomotherium, and he found a 

 striking similarity in crown patterns. Douglass doubted that this form had three incisors and said 

 that, if it did, they must have been exceedingly small or placed anterior to the canine. Undoubtedly 

 they were very small, and I believe that they were not reduced in number. 



