¢ 
1884.] 543 [Cope. 
tympanic and paroccipital processes. It is not distinetly 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 postglenoid processes. It is partially 
enclosed by the robust rounded ledge of the squamosal bone, which 
separates it from the postglenoid 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 
postgléenoid process, and that of the paroccipital process. The postglenoid 
process is robust, much as in the large species of Merycocheerus, and not 
compressed as in Merychyus leptorhynchus and M. wrenarum. The zy go- 
matic arch is slender. The elevation of the posterior part of the zygo- 
matic process of the squamosal has a diflerent form from that seen in the 
species last named. It is angulate, not rounded. The position of the 
angle is different from that in JZ. eygomaticus in being more anterior, 
marking a point well in front of the anterior base of the postglenoid pro- 
céss. 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 pariéto-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 Hucrotaphus and 
Oreodon, The anterior and median vertical ridges are very prominent, 
and the posterior vertical border of the posterior column projects to a slight 
PROC. AMER. PHILOS. 800. xxt. 116, 8Q. PRINTED JuNE 16, 1884. 
