38 



THE MERYCOIDODONTID/'E 



muzzle is narrow, and the forward ridge from the anterior zygomatic pedicle soon dies out on the 

 side of the face. The canine alveolus is prominent. The narrow nasal bones are unreduced and 

 appear to have been posteriorly truncated. The pars facialis of the lacrimal bone is small, and 

 there is no antorbital fossa. The frontal bones are proportionally small but unreduced. There is 

 a median anteroposterior concavity toward the after part, while transversely these bones are gently 

 decurved from the sagittal suture to the supraorbital margin. The orbits are posteriorly open, 



Fig. 13. — Protoreodon fumilus (Marsh). Skull and jaw. FT. Cat. No. 11891 Y.P.M. 1/2 nat. size. 



rather large, and almost centrally located, and they look nearly completely outward. The temporal 

 ridges are short and unite rapidly just behind the postorbital constriction to form a very high and 

 thin sagittal crest, more than a third of the skull length. The supraoccipital crest is not much 

 produced beyond the line of the condyles, and the large wings are well apart. The brain case is very 

 narrow and elongate, with no marked convexities. The external auditory meatus is small and is 

 directed somewhat upward and backward. The basicranial axis is moderately steep. The palate is 

 narrow and is flat anteriorly, becoming vaulted aft, and the U-shaped palatonarial border is opposite 



F, c- 14. — Protoreodon fumilus (Marsh). Left half, inferior view of skull. PT. Cat. No. 11891 Y.P.M. 3/4 nat. size. 



Fig. 15. — Protoreodon fumilus (Marsh). Superior view of mandibular ramus. PT. Cat. No. 11891 Y.P.M. 3/4 nat. size. 



the hypocone of M\ The glenoid articular surface is small, of nearly the same dimensions in both 

 diameters, and somewhat convex. The anteroposteriorly compressed postglenoid process is nearly 

 as long as the glenoid surface and has an oblique external border. The bulla is very tiny. The 

 paroccipital process is broken away, but the base is L-shaped. This process is certainly slender and 

 probably less elongate than in Merycoidodon. Index: 0.345. 



Mandible: The symphysis is strong and somewhat convex in profile, and the mental tubercle is 

 large. The symphysiodental angle is 47°. The inferior border of the horizontal ramus is convex 

 below the molars. The condyle is wide, convex, and set well in from the posterior border of the 

 ascending ramus. 



