88 MEMOIRS OF THE CARNEGIE MUSEUM 
practically the same position as in the Oligocene genus, 7. ¢., just lateral to the ridge 
of the alisphenoid which leads to the pterygoids. The skull is distorted in this re- 
gion, so that the peculiar conditions of the pterygoids, which Professor Scott describes 
(87, p. 283), cannot be ascertained from this specimen. The parietals extend well 
down on the side of the cranium and terminate superiorly in the high and sharp 
sagittal crest, which is rounded from before backward in a manner similar to what is 
observed in some other American forms. The sutural contact between the frontal, 
supraoccipital, and the squamosal is entirely obliterated. The frontals are very 
broad and much inflated over the orbits, terminating laterally in a heavy process, 
which meets its fellow of the jugal; the two are well codssified and form a heavy 
vertical bar, which completely encloses the orbit posteriorly. The orbit is of large 
size and faces forward and slightly outward. Immediately in front of the sagittal 
crest is a broad canal, which extends obliquely upward and backward, apparently 
piercing the cranial wall (see Pl. LVI). The exit of this canal leads into a depres- 
sion on the frontals, which is of considerable depth and triangular in outline. This 
depression extends outward laterally by means of two large grooves, one on either 
side, running parallel with the temporal ridges, and by means of a broad anterior 
groove, which is continuous with the depressed median area of the frontals. On 
account of the enormous inflation of the frontals over the orbit and the great lateral 
extent of the postorbital process the eye was placed lower down and had a more 
direct forward look than in the older types of this family (see Pls. LV, LVI). 
The zygomatic process of the squamosal has an enormous development, which 
seems to be relatively quite as great, if not greater, than is the case in the earlier 
forms. The lambdoidal crest descends steeply to a point immediately above the 
base of the paroccipital process; the border of the arch then rises again to form a 
broad, thin process similar to that in Sus, the peccary, and other ungulates. An- 
teriorly the zygomatic process forms the sutural contact with the jugal at the base 
of the orbital process. The temporal fossa thus has a tremendous transverse diameter, 
which is one of the chief characteristics of the cranium in this family. The glen- 
oid cavity is well defined and ‘its anterior border is provided with a strong buttress 
(the zygomatic process of the jugal referred to above), which seems to be a mark of 
evengreater specialization in this genus, than in the John Day forms, and has 
already been referred to in previous papers (81, pp. 49-51). 
The jugal, as has been stated by Marsh, Scott, and others, constitutes one of 
the most extraordinary features of the skull in this family. Anteriorly the jugal 
extends but little on the side of the face, uniting by suture with the maxillary and 
the lachrymal. In its backward extension the upper margin forms the lower half 
