78 



THE MERYCOIDODONTID/E 



decurvature above the large orbits is less pronounced than in E. major. The temporal ridges unite 

 just in front of the glenoid surfaces to form the normal sagittal crest, about one-fourth of the skull 

 length. The brain case is large and moderately full, with a low lateral ridge. The basicranial axis 

 is shallow. The wide palate is flat anteriorly, gradually becoming vaulted posteriorly. The palato- 

 narial border is posterior to the last molars. The glenoid surface is long, wide, and very slightly 

 convex, while the postglenoid process is anteroposteriorly compressed and has an oblique external 

 surface. It is not large. The bulls, although missing, were undoubtedly large. Index: 0.72. 



Foramina: The infraorbitals are above P 3 . The supraorbitals lie 21 mm. apart, and the pos- 

 terior palatine foramina are opposite P\ 



Dentition: The premolars of the plesiotype are typical of Eporeodon, and, although consider- 

 ably worn and somewhat checked, the pattern is discernible. The superior molar-premolar index 

 is 0.88, almost exactly that of E. major, though the length of the dental series is about ten per cent 

 less. 



Fie. 38, 



-Eforeodon major hybridus (Leidy). Fragmentary skull. HT. Cat. No. 10860 A.N.S.P. 1/2 nat. size. 



(Redrawn from Leidy, 1869.) 



Discussion: The holotype unfortunately lacks the premolars and the cranial region, so that we 

 cannot be certain of the pattern of the former nor determine the presence or absence of bulls. 

 Furthermore, we do not know the exact geological horizon of the type. However, I believe that my 

 selection of the Peabody Museum specimen as a plesiotype is correct. If so, there can be no doubt 

 of its reference to Eporeodon. This specimen was collected in Colorado in 1873 by E. Devendorf, 

 and the matrix indicates its geological position as uppermost middle Oligocene or lowermost upper 

 Oligocene. I believe that the latter is correct. 



While this species is more brachycephalic (based on the plesiotype) than E. major, it is more 

 nearly in agreement otherwise in size and proportions than with the other species of this genus, and 

 I am therefore referring it to E. major as a subspecies. It is interesting to note that in the cata- 

 logue of the Philadelphia Academy the type is listed under the name of Oreodon major. There 

 is reason to believe that this classification dates from Leidy's time. 



Eporeodon major relictus Loomis 1924 

 Fig. 39; PI. VI, figs. 4-5 



Original Reference: Miocene oreodonts in the American Museum. Bull. Amer. Mus. Nat. Hist., LI, 

 Art. 1, pp. 36-37, fig. 26 {Eforeodon relictus). 



Type Locality: Six- miles west of American Horse Creek, Pine Ridge, South Dakota. 



Geologic Horizon: Lower Miocene (lower Rosebud). 



Type: Holotype, Cat. No. 13813 A.M.N.H., considerably mutilated skull. 



