76 THE MERYCOIDODONTID^ 



John Day they are round. The carpals are much lower than those of Mesoreodon, and there is no 

 facet between the trapezoid and Mc. III. The trapezium is larger than that of Mesoreodon and 

 overlaps the side of Mc. II. The unguals resemble those of Mesoreodon intermedins but are unlike 

 those of M. chelonyx. 



Discussion: Matthew (1901 A, p. 397) wrote of the skull: 



This variety shows less tendency toward the long and flat-topped Promcrycocharm type of skull, and more 

 toward the Merychyus and Merycochocrus type, short and round-topped. A similar varietal differentiation is 

 observable in the more Promery cochcerus-Wkt E. occidentalh , but in the John Day species the long, flat-topped 

 type of skull runs to excess, while in Colorado we have the short, round-topped one prevalent. 



In the broad features the above is true, but the skull index of E. m. cedrensis, 0.56, is not far 

 above the dolichocephalic-mesocephalic borderline, while the index of E . occidentalh is 0.63, or close 

 to the brachycephalic line. E. trigonocephalies, from Oregon, is well within the brachycephalic 

 range, with an index of 0.74. In other words, in the genus Eporeodon the major number of species 

 are of the mesocephalic type, whether from the West Coast or the Great Plains, and it is in this 

 class that E. m. cedrensis takes its place. 



When Loomis (1924B, pp. 36-37) established the species E. relictus, he wrote: "Other speci- 

 mens of the same species are No. 13814 and No. 8949, with the latter of which there is a consider- 

 able part of the skeleton, but unfortunately the individual is a young one." 



The specimen, Cat. No. 8949 A.M.N.H., is the material selected by Matthew as the holotype 

 of E. m. cedrensis. Loomis was quite right in noting the resemblances between his holotype of 

 E. relictus and Matthew's type of E. m. cedrensis. 



The type skulls of both subspecies are considerably damaged, but the major differences between 

 the two lie in the geologic age and geographic locality. Matthew's species is of upper Oligocene 

 age from Colorado, and Loomis' is from the lower Miocene of South Dakota. If the two forms 

 are the same, it seems to indicate a very conservative and persistent species. 



The two skulls are very nearly the same in size and apparently have the same skull index. 

 The palates are of the same width, the lengths of the superior molar series are probably the same, 

 although M 3 is not erupted in Matthew's type, the zygomata originate above P 4 in both, and the 

 distance from the condyles to M 3 is the same. 



The premolar length of E. m. cedrensis is 44 mm. as opposed to 40 mm. for E. m. relictus. 

 This may result from the fact that the milk premolar series in Matthew's type is longer than the 

 permanent series. The E. m. relictus skull is slightly wider at the orbits, which again may be an 

 adult development. I hesitate to include the two together, first, because E. m. cedrensis is based on 

 an immature skull, and the characters shown therein may not present a true picture of the adult 

 characters, and, second, because the interval between upper Oligocene and Miocene time was prob- 

 ably of considerable duration, while the third reason, that of difference in geographic locality, may 

 not be of great importance, except that the merycoidodonts in general seem to be more or less 

 localized by species. 



For the present I prefer to consider these two forms as separate entities but with the thought 

 that future material will probably show them to be the same species. 



Eporeodon major cheeki Schlaikjer 1934 

 PL VII; PI. XXXIX, fig. 2 



Original Reference: Three new oreodonts. Proc. Boston Soc. Nat. Hist., XL, pp. 220-223. 



Type Locality: SJl%, Sec. 21, T. 20 N., R. 60 W., Goshen County, Wyoming. 



Geologic Horizon: Lower Miocene (lower Harrison). Approximately 200 feet above the Brule-lower 

 Harrison contact. 



Type: Holotype, Cat. No. 17765 M.C.Z., nearly complete skeleton. Collected by E. M. Schlaikjer. 

 Named in honor of David B. Cheek, the discoverer of the specimen. 



