40 THE MERYCOIDODONTID/E 



Protoreodon species Russell and Wickenden 1933 



Original Reference: An upper Eocene vertebrate fauna from Saskatchewan. Trans. Roy. Soc. Canada 

 (3), Sect. 4, XXVII, p. 64, pi. I, fig. 11. 



Locality and Geologic Horizon: Saskatchewan, Canada; upper Eocene (Swift Current). 

 Material: Cat. No. 8665 N.M.C., right P 4 . 



Discussion: The authors provisionally refer this tooth to Protoreodon and consider that it may 

 represent an undescribed species of that genus. They wrote as follows: 



The cusp pattern is similar to that of the P 4 of P. parvus, but the present specimen is only of about one half 

 the size. The narrowly subquadrate outline and small size of this tooth distinguishes it not only from the 

 described species of Protoreodon, but also from other contemporary artiodactyl genera. Dimensions: antero- 

 posterior diameter, 3.2 mm.; transverse, 5.4 mm. 



Genus HYOMERYX Marsh 1894 



Table 1 



Hyomeryx breviceps Marsh 1894 



Figs. 16-17 



Original Reference: Description of Tertiary artiodactyles. Amer. Jour. Sci. (3), XLVIII, pp. 267- 

 268, fig.19. 



Type Locality: White River, Utah. 



Geologic Horizon: Upper Eocene (Uinta — Hor. C). 



Genoholotype: Cat. No. 10017 Y.P.M., fragmentary parts of skull and jaws, together with a few frag- 

 ments of skeletal material. Collected by J. W. Chew and Matt Forshey, 1877. 



Specific Description and Discussion: Marsh's original description is accurate in so far as can 

 be determined from this fragmentary material. The skull is about two-thirds the size of that of 

 Protoreodon -pumilus. The premaxillaries are very much reduced and are firmly coossified with the 



Fig. 16. — Hyomeryx breviceps Marsh. Crown Fig. 17. — Hyomeryx breviceps Marsh. Lateral 



view of P 3 to M 2 . GHT. Cat. No. 10017 Y.P.M. view of maxillary with teeth. GHT. Cat. No. 



Nat. size. 10017 Y.P.M. Nat. size. 



maxilla:. There appear to have been no superior incisors, but the alveolar parapet is slightly broken 

 in this area, and there may have been at least one very tiny incisor, although no evidence of it now 

 remains. It is very doubtful whether or not the two premaxillaries joined. The evidence points to 

 a negative answer. 



The mandibles are less robust than those of Protoreodon but had a strong symphysis, straight 

 in profile. 



Professor Marsh believed that there were four functional digits in the manus, with the first 

 "probably represented in a much reduced form. In the hind feet, also, there are four functional 

 digits, and a remnant of the fifth is still retained." 



Dentition: As stated above, the superior incisors appear to be lacking. The upper canines are 

 smaller than those of Protoreodon pumilus. They are followed by a diastema. P 1 is double-rooted. 



