A NEW MYLODON. 321 
squamosal process, is slightly less than the width between the rounded supra- 
orbital processes. The heavy occipital crests meet the strong sagittal crest 
on the braincase in a slightly overhanging ridge, which passes anteriorly into 
the smooth surface of the frontal region, with a poorly defined prolongation to 
the blunt supraorbital angle. The sides of the braincase are nearly vertical and 
their surface is much roughened for the attachment of the temporal muscles. 
Anterior to the orbit the rostrum is broader and nearly square, with much less 
elongation than in Paramylodon. The tips of the nasals, though slightly dam- 
aged, seem to have been convexly rounded, and did not project beyond the sides 
of the muzzle. The latter is slightly inflated and smooth. 
The outline of the nasal opening, viewed from in front, is a trapezoid, of 
which the base, formed by the bones of the palate, is parallel to the top, which 
is formed by the nasals. The width of the base is nearly double that of the top, 
so that the sides (7. e. the maxillaries) converge dorsally. There is no indica- 
tion of a bony nasal septum. 
The posterior view of the skull is almost horseshoe-shaped in outline, with 
the convexity dorsal. The extreme narrowness of the braincase is here empha- 
sized by the fact that the extreme height of this occipital face is considerably 
ereater than the width, whereas in the Colorado skull, as in Paramylodon, this 
face is much wider than high, so that its outline is nearly a semicircle. A strong 
median ridge extends from the upper lip of the foramen magnum dorsally to the 
lambdoid ridge which forms the boundary of the posterior face of the skull. 
On each side between the condyle and the lambdoid ridge is a triangular depres- 
sion, whose surface is marked by several small ridges, for the attachment of the 
digastric muscle. The foramen magnum, as in Paramylodon, looks downward 
as well as backward, and about one half the surface of the condyles is ventral. 
In ventral view, (Plate 2, fig. 3) the palate is seen to be long, contracted 
posteriorly and expanded anteriorly with its greatest width just in front of the 
first tooth. In contrast to the form of palate shown by Mylodon robustus, 
that of the present species is produced some 50 mm. anterior to a line joining 
the front edges of the first teeth, and is long, narrow, and very slightly expanded 
anteriorly, instead of being broad, blunt, and with widely divergent sides. The 
interpterygoid fossa is extremely deep and narrow. Its walls are parallel, and 
anteriorly converge to forma pointed arch. The pterygoids are likewise parallel 
to the long axis of the skull and diverge but little ventrally in contrast to those 
of the Colorado skull and Paramylodon, in which the pterygoids flare widely 
apart. 
