Cope. | 548 (Jan. 18, 
file descends at the orbits into the nasal vacuities, which cause a deep ex- 
cavation of the facial plate of the maxillary region. The small nasal 
bones form a promontory below the level of the orbits, whose supe- 
rior borders are convex. The maxillary bones rise at the end of the 
muzzle, forming, probably, with the confluent premaxillaries, a sub- 
quadrate projection, ‘The superior side of this process is concave on its 
interior aspect forming a curved suture of an expanded nasal bone. Its 
anterior edge is also concave on their inner side, as though adapted to 
a forward-looking nareal opening. This anterior border is produced 
downwards into a free conical process which bounds the canine alveolus 
in front. This I suppose is all that there is of the alveolar portion of the 
premaxillary bone. The corresponding part of the other side is lost. 
There is a well-marked preorbital fossa. Its supero-interior border bounds 
the huge nasal vacuity on each side. The nasal bones form a narrow 
promontory, with convex superior face, which extends a little beyond a 
line connecting the middles of the preorbital fosse. The vacuities exca- 
vate the frontal bones as far back as a line connecting the middles of 
the supraorbital borders. The frontal bone is thus of a A-shape. The 
anterior temporal ridges are well defined, but do not reach the free edge 
of the frontal bone. Their union into the sagittal crest is gradual. The 
brain-case is moderately elongate, the postorbital process of the malar 
bone marking the middle of the total length. In profile the posterior part 
of the skull is nearly straight. The sagittal crest is gently convex, and 
is not so deeply bifurcated posteriorly as in most other forms, The posterior 
temporal crests are expanded laterally, and continue well developed to 
above the meatus auditorius, into the superior edge of the zygoma, They 
are not continued downwards on the occiput, as in most of the other genera 
of the family, but resemble the species of Merychyus more than any 
others in this respect. The temporal fossa has a wide floor, due to the 
lateral extension of the meatus auditorius, and the glenoid portion of the 
squamosal. The superior edge of the zygomatic process of the squamosal 
is little elevated, and is regularly convex. The process is not produced 
as far anteriorly as the posterior border of the orbit. The malar bone is 
remarkable for its depth, exceeding in this respect any species of the 
family yet known. Its external face slopes obliquely outwards below, but 
not very much, and is slightly and uniformly convex. Its inferior edge 
is thickened and descends anteriorly, and then thins and rises continuous- 
ly to the zygomatic process of the squamosal. 
The occipital aspeet of the skull is wide and low. Its superior region 
is slightly convex and roughened on each side of the median line. From 
and below this valley, the middle line presents a sharp carina, which dis- 
appears in a narrow convexity above the foramen magnum. Between 
this convexity and the meatus auditorius, the surface is concave. The 
occipital condyle is small, and the exterior half is more extensive than the 
posterior half. The paroccipital process is large. Its base diverges from 
the occipital condyle, and is adherent by its anterior face to the otic bulla, 
