1884.] o4cO [Cope. 



tympanic and paroccipital processes. It is not distinctly continuous over 

 the auricular meatus. The paroccipital process is elongate and acumi- 

 nate, and becomes compressed so as to be anteroposterior for the greater 

 part of its length. The auricular meatus occupies but a small part of the 

 space between the posttympanic and postgienoid processes. It is partially 

 enclosed by the robust rounded ledge of the squamosal bone, which 

 separates it from the postgienoid process. This ledge is much more devel- 

 oped than in any other species of this family known to me. The bulla of 

 the petrous bone is longer anteroposteriorly than transversely, and its 

 anterior and posterior borders coincide with the anterior border of the 

 postgienoid process, and that of the paroccipital process. The postgienoid 

 process is robust, much as in the large species of Merycochcerus, and not 

 compressed as in Merychyus leptorhynckus and M. %renarum. The zygo- 

 matic arch is slender. The elevation of the posterior part of the zygo- 

 matic process of the squamosal has a different form from that seen in the 

 species last named. It is angulate, not rounded. The position of the 

 angle is different from that in M. zygomaticus in being more anterior, 

 marking a point well in front of the anterior base of the postgienoid pro- 

 cess. The border which connects the angle with the supra-auricular crest 

 is then not vertical as in the species just mentioned, but is oblique, and it 

 is also somewhat concave. The malar bone is shallow and stout, with 

 truncate edge below. The squamosal process enters it to below the poste- 

 rior third of the orbit. The postfrontal process is slender, and the post- 

 orbital process of the malar is elongate, meeting the former opposite the 

 middle of the orbit. It is thus longer than in any species of the family 

 known to me. 



The frontal foramina are separated by an interspace equal to four-fifths 

 the distance between each and the superciliary border. The parieto-squa- 

 mosal suture ascends posteriorly in a nearly straight line to within M. .015 

 of the posterior zygomatic crest. The posterior squamosal suture then 

 turns directly downwards, reaching the depressed portion of the crest 

 where it bounds the huge mastoid fossa and foramen. 



The posterior part of the mandibular ramus, shows a regularly convex 

 angular border commencing just below the condyle. The coronoid pro- 

 cess is quite small and the short connecting edge between it and the con- 

 dyle is not excavated below the level of the latter. The articular face of 

 the condyle is directed upwards, and on the internal third, presents a face 

 posteriorly also. The ramus diminishes rapidly in depth anteriorly. The 

 masseteric fossa does not descend below the level of the second true molar, 

 and is not sharply bordered anywhere. The internal pterygoid fossa on the 

 other hand occupies the entire inner face of the angle between the condyle 

 and the inferior border, and anteriorly to the line of the last inferior molar 

 tooth. ' 



The superior true molars have short crowns, as in Eucrotaphus and 

 Oreodon. The anterior and median vertical ridges are very prominent, 

 and the posterior vertical border of the posterior column projects to a slight 



