32 OREODON. 
that of Anoplotherium. Its median portion bulges backward above the foramen 
magnum, and is concave below the summit of the inion. The lateral portions of 
the surface are directed outwardly from the median, and are moderately concave, 
but relatively much less than in the Camel. 
The lateral margin of the inion, or the occipital crest, is relatively less prominent 
than in the Camel; and at its lower part is formed, as in the Deer and other rumi- 
nants, by the elevated border of the pars squamosa and a process of the pars petrosa 
intercalated between the former and the occiput. 
The occipital foramen is transversely oval and emarginate above.. 
The condyles resemble those of the Anoplotherium, and do not advance upon 
the basilar process inferiorly as in the Camel, Deer, and other-ruminants. Their 
position corresponds pretty closely with that which they have in the Camel; and 
their angle and superior and inferior faces present in the same direction. 
Inferior View.—(PI. IIL Fig. 1; V.2,3; VI.3.) The base view of the skull, 
in its general form, much resembles that of Anoplotherium; but it is relatively 
broader in comparison with its length, and presents numerous peculiarities. The 
basilar process slopes on each side from a central crest, which expands at the con- 
dyles and at its junction with the post-sphenoidal body. The surface of the latter 
is smooth, slightly convex, and inclines slightly upward in its direction forward. 
(HOE wissveVeF 22) 
The pterygoid processes commence a little in advance, and to the outside, of the 
position of the spheno-basilar junction, and are very oblique in their course down- 
ward and forward. To their inner side is a shallow groove, directed to the foramen 
lacerum, for the reception of the Eustachian tube. 
The paramastoid processes form the infero-lateral terminations of the occiput, and 
are conspicuous objects either in the lateral or posterior view of the skull. They 
are relatively about as long and strong as those of Anoplotherium, but are nearly 
vertical, or bent slightly forward and outward. Their form is elongated pyramidal, 
and the outer portion of their base abuts upon the posterior process of the pars 
petrosa, as in the Deer; while the antero-internal portion rests upon the auditory 
bulla. Antero-externally the para-mastoid process is longitudinally excavated, and 
between its base and the pars petrosa it incloses the stylo-mastoid foramen, and in 
advance of this the pit of reception for the styloid process. (III. 1; V. 2.) 
The mastoid process is small, as in all ruminants, and is a compressed eminence or 
ridge forming the posterior boundary of the meatus auditorius externus. It does not 
descend as low as the bottom of this, and projects between the auditory process 
from which it is separated by a notch, and the base of the paramastoid process. 
The auditory process constitutes the antero-inferior boundary of the meatus, and 
inferiorly forms a ridge-like vaginal process curving forward and inward to the 
auditory bulla with which it is continuous. 
The latter is relatively very small to what it usually is in ruminants, and cor- 
responds in this respect with Anoplotherium. It is convex, surmounted by the ridge 
just indicated, rests against the paramastoid process posteriorly, and is continuous 
with the bony process of the Eustachian tube anteriorly. Internally, as in existing 
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