72 THE MERYCOIDODONTID/E 



Specific Characters: The skull is large, robust, and mesocephalic. Both zygomata are largely 

 missing, but the malar portion is moderately heavy and deep, with the maximum expansion probably 

 anterior to the glenoid surface. The nasal bones are nearly flat transversely and are of fairly uni- 

 form width to a point near the posterior part whence the width rapidly diminishes until the bones 

 terminate in points aft of the antorbital margins. The lacrimal bone has a large pars facialis, and the 

 lacrimal fossa is mediumly deep and large. The frontals are wide and unusually flat, with a shallow 

 medial depression and very gentle convexities above the orbits. These bones extend in advance of the 

 lacrimals. The orbits are small. The temporal ridges unite just aft of the postorbital constriction 

 to form a short, thin, and high sagittal crest, about one-fifth of the skull length. The supraoccipital 

 crest is posteriorly well produced, and the wings were apparently moderately widespread. The 

 brain case is well developed, without marked lateral ridges. The external auditory meatus is large 

 and tubular and is directed somewhat backward. The palate is wide and arched, and the U-shaped 

 palatonarial border is well back of the last molars. The angle of the basicranial axis is shallow. 

 The glenoid surface is slightly concave. The postglenoid process is stout, and the two diameters are 

 nearly the same, with the transverse one slightly greater. The bullas are large and oval in shape, 

 and the anteroposterior diameter forms an angle with the sagittal plane. The distal surface is pitted. 

 The base of the paroccipital processes is closely applied to the posteroexternal area of the bullas, 

 and the processes are diamond-shaped in cross section at about mid-length. Index: 0.54. 



Foramina: The infraorbitals are above the posterior part of P 3 . The supraorbitals are 20 mm. 

 apart. The posterior palatine foramina are apparently on a line between P 4 and M 1 . 



Dentition: The crowns of most of the teeth are incomplete, but those that remain do not show 

 any deviation from the generic type. The superior molar and premolar series are of nearly equal 

 length, producing an index of 0.94. 



Discussion: This form was not common, if we can judge from the number of skulls referable 

 to the species in the Marsh and Cope collections. 



Eporeodon longifrons perbullatus Thorpe 1921 

 Figs. 35-37 



Original Reference: John Day eporeodons, with descriptions of new genera and species. Amer. Jour. 

 Sci. (5), II, pp. 106-107, figs. 9-10 (Eforeodon ferbullatus) . 



Type Locality: Bridge Creek, John Day Valley, Oregon. 



Geologic Horizon: Lower Miocene (HT) and upper Oligocene (PTs) (upper and middle John Day, 

 with gray and green matrix respectively). 



Types: Holotype, Cat. No. 11011 Y.P.M., collected by S. H. Snook in 1874. Paratypes, Cat. Nos. 12319 

 and 12320 Y.P.M., collected by L. S. Davis in the same year. All skulls, with mandibles. 



Specific Characters: The skull is mesocephalic and about the length of that of E. pacificus. 

 The zygomata are medium in size, rising posteriorly and with the maximum expansion at the anterior 

 part of the glenoid surface. The nasal bones are wide, moderately convex transversely, and poste- 

 riorly truncated. The pars facialis of the lacrimal is large and bears a large, deep fossa. The 

 frontals are wide and nearly flat, except for a slight medial depression and a short supraorbital con- 

 vexity. The orbits are unusually large for the skull size. The temporal ridges unite well aft, 

 about in a plane through the anterior of the postglenoid tubercles. The sagittal crest is not high 

 and is short, being less than one-fourth of the skull length. The supraoccipital crest is well pro- 

 duced, but the wings are only moderately expanded. The brain case is well developed and is wider 

 than in E. leptacanthus, with a prominent convexity along the parietosquamosal suture. The 

 external auditory meatus is upwardly and backwardly directed. The wide and slightly vaulted 

 palate is produced but a short distance beyond the last molars, and the V-shaped palatonarial border 

 is nearly on a line with the posterior of M 3 . The glenoid articular surface is gently convex, while 



