324 A NEW MYLODON. 
19 mm., transverse 15, thus much the same as in M. harlani (see Cope, 1895). 
The beveled surface of the crown is 20 long. The tooth projects about 19 mm. 
from the socket and is separated from the second by an interval of only 9 mm. 
The second upper tooth likewise has its anterior portion recurved so that the 
crown is directed backward at a small angle to the palate. The front face is 
slightly beveled by contact with the posterior facet of the first lower tooth, but 
the crown opposes the second lower tooth. The general outline in section is 
an ellipse, with a longitudinal diameter of 36 mm., transverse 17, at the alveolus. 
The tooth figured by Cope (1895) as the second upper molar of M. harlani is 
sunilar but with a much greater bevel on the anterior face. 
The third upper tooth has three lobes, an outer with nearly square outline, 
and two inner, of which the posterior is much the longer with nearly parallel 
sides: and rounded ends. A shallow sulcus separates these two lobes at the 
lingual side of the tooth. The posterior lobe forms a long heel which is bent at 
an angle of nearly 45 degrees from the axis of the tooth row toward the median 
side. The outline is not essentially different from what Cope (1895, pl. 10) 
figures for M. harlani and M. renidens; and as nearly as may be judged from a 
photograph, the tooth is practically the same in the Colorado specimen. The 
anterior inner lobe is about opposite the single outer lobe, but so deflected is 
the posterior lobe that its tip is in the same straight line as that of the first. 
The extreme breadth anteriorly is about 24 mm.; the length in the axis of the 
tooth row from tip of the anterior inner lobe to the back of posterior lobe is 
29.6 mm., while the diagonal from the point of the latter to the tip of the outer 
lobe is 33 mm. : 
The fourth upper tooth is narrow and compressed in the long axis of the 
toothrow, but is set at an angle of nearly 45 degrees to the latter. It has three 
lobes, as does the preceding tooth, two inner and one outer, but the last is con- 
siderably in advance of the anterior inner lobe; and the posterior inner lobe is 
not much elongated, apparently much less so than in M. harlani and M. renidens, — 
as figured by Cope. In this respect the Colorado skull seems to resemble these 
two species and to differ from our specimen. There is thus a greater dissimilarity 
in the shape of the third and fourth upper teeth of our animal than appears in 
the three others. So compressed is it, that its outline is roughly a parallelogram, 
slightly concave on the posterior outline. The dimensions are: — tip of anterior 
inner lobe to tip of outer lobe 30 mm.; from the latter point to tip of posterior 
inner lobe 35.5 mm.; front of anterior inner to end of posterior inner lobe 19 mm. 
The fifth upper tooth differs decidedly from that of M. harlani and M. reni- 
