ON A NEW SPECIES OF MACRAUCHENIA (M. BOLIVIENSIS) 409 
end has a sharply defined rounded margin, which can be traced to 
the anterior boundary of the occipital foramen ; so that the occipital 
condyles certainly did not coalesce in the middle line. 
The paramastoid process is broken off rather above the level of 
the lower boundary of the occipital condyle; but, from the thinness 
of the fractured edge, I imagine it did not extend much further. It 
is broad and flattened, the direction of its greatest diameter being 
from behind and without, inwards and forwards. Its posterior face 
is directed as much inwards as backwards, and its outer margin is 
sharp, except towards the lower end, where it becomes rounded. 
Internally, it thickens before rejoining the exoccipital, in front of, and 
external to, the precondyloid foramen. The upper part of its anterior 
and external face is evidently rough and has united with the mastoid, 
now completely broken away ; but it is difficult to say how far down- 
wards the sutural face extended. The posterior boundary of the 
jugular foramen is preserved on the inner side, and in front of, the 
thick inner edge of the paramastoid. 
The sagittal crest is continued forwards from the triangular pro- 
minence common to it and the occipital crest, and at once becomes 
very thin and sharp. It is broken off at a very short distance from 
its commencement, and at this point it is a quarter of an inch high. 
Its superior margin is not parallel with the contour of the middle line 
of the parietal region, but has a more marked upward inclination, so 
as to lead one to suppose that the crest rose to a considerable height 
in the middle of the synciput,—a conclusion which is strengthened 
by the great thickness of the parietals (of whose median suture no 
trace is visible) in the middle line. The transverse section presented 
by the anterior broken edges of these bones 1s, in fact, triangular, and 
the height of the triangle from its apex, which corresponds with the 
base of the crest, to its base (the concave inner wall of the cranium) 
is nearly 0-4 of an inch. 
In viewing the fragment of the occiput from within, one is sur- 
prised by the great thickness of the supra-occipital region, the bone 
immediately above the middle of the occipital foramen being half an 
inch thick. A well-marked ridge, defining the interior boundary of 
the cerebellar fossa, is continued downwards, forwards, and outwards, 
from the anterior boundary of the thick roof of the occipital foramen. 
There is no venous canal traceable above the inner aperture of the 
precondyloid foramen. 
If the occiput of Macrauchenia Boliviensis be restored by reversing 
the outlines of the right half (as in Pl. VI., [Plate 32.] fig. 3), thus 
supplying the wanting left moiety, the following measurements may 
