EPOREODON 69 



in both diameters and are produced in advance of the lacrimal bones. The orbits are large. The 

 temporal ridges unite at the postorbital constriction. The sagittal crest is low and long, at least a 

 third of the skull length. This skull shows one of the rare instances among merycoidodonts where 

 the interparietal is not fused with the parietal. The supraoccipital crest is missing but was appar- 

 ently normal. The brain case was well rounded and has only a slight ridge along the parietosqua- 

 mosal suture. The external auditory meatus is medium-sized and is directed chiefly upward and 

 outward. The palate is wide and not highly vaulted, with the U-shaped palatonarial border on a 

 line with the posterior edge of M 3 . The basicranial axis is shallowly inclined. The glenoid surface 

 is normal. The postglenoid process is small, with an oblique external border, and is in contact with 

 the bulla. The bullae are very large and deep and are transversely compressed into an elliptical out- 

 line. The surface is pitted. The paroccipital processes are moderately small, five-sided superiorly, 

 four-sided medially, and triangular distally in cross section. These bear a posteroexternal ridge 

 and are anterointernally concave where they are closely pressed against the bulke. Index: 0.58a. 



Mandible: The symphysiodental angle is slightly less than 45°, and the profile of the chin is 

 somewhat concave. The mental tubercle and the angle are not prominent. The posterior border of 

 the ascending ramus is nearly perpendicular. The condyle is low, inset, transversely wide, and 

 anteroposteriorly narrow. The coronoid process is low and not posteriorly deflected. The sigmoid 

 notch is shallow and wide open. 



Foramina: The infraorbitals lie above the middle of P 3 . The supraorbital foramina are about 

 1 5 mm. apart and are situated aft of a line through the middle of the orbits. The stylomastoid 

 foramen is nearly the size of the tympanohyal pit. The foramen ovale is large, and there is no trace 

 of a foramen rotundum. The posterior palatines are opposite P 4 . 



Dentition: P 4 is noteworthy, as it has two very small anterior fossettes, after the pattern of the 

 preceding premolars. This is an unusual condition, and whether it is an abnormality or a specific 

 character I cannot say. Both P 4 are alike and are otherwise normal, as are the other molars and 

 premolars. The superior and inferior molar-premolar indices are 0.88. In general the dentition is 

 very much like that of E. sodalis, except for the construction of P 4 . 



Discussion: This type was not found in place, and Douglass said that it was barely possible 

 that it came from the upper (White River) beds. 



This species is a typical member of the Eforeodon genus and lies within the E. major group. 

 If it were not for the unusual structure of P 4 , I should include this form with the subspecies of 

 E. major, as a geographic variant and possibly as a geologic one as well, though there is doubt on 

 the latter point. 



Eporeodon helenae (Douglass) 1901 

 PI. IV, figs. 4-8 



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

 Soc. (2), XX, pp. 243, 253, 265 {Eucrotaphus helemr). 



Type Locality: Northeast of Toston, Broadwater County, Montana. 



Geologic Horizon: Upper Oligocene (Toston). Collected in a bed of clay which contained nodular layers. 



Type: Holotype, Cat. No. 765 CM., skull and mandible, lacking zygomata, supraoccipital crest, and 

 anterior part in front of P 2 — a young individual, with deciduous premolars but all the true molars. 



Specific Characters: This species is founded on an immature skull and jaws, with dentition 

 in part deciduous. The skull is small, about the same length as that of E. parvus but more meso- 

 cephalic. The zygomata originate over the back part of M 1 and are widest at the front of the glenoid 

 surfaces. The malar part is deep and robust. The nasal bones are broad, and they narrow gradually 

 and uniformly backward to end in points on a line with the antorbital margins. They are trans- 



