Cope.] Oio [ Jan> is, 



file descends at the orbits into tlie nasal vacuities, which cause a deep ex- 

 cavation of the facial plate of the maxillary region. The small nasal 

 hones form a promontory below tbe level of tbe 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 fossse. 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 '^-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 aspect 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, 



