322 A NEW MYLODON. 
The mandible, in comparison with that of the latter genus, is of especial 
interest. The coronoid process is smaller, and the ramus, instead of tapering 
strongly towards the symphysis is of nearly the same depth at that point as at 
the level of the last molar, which is in correlation with the less elongated rostrum. 
Certain of the cranial bones and the teeth require further mention. 
The nasals are broad anteriorly, with a combined width of 70 mm. at the 
nasal orifice but taper rapidly back to about the level of the orbit, where, on 
account of the nearly complete disappearance of the median boundary through 
fusion and by reason of a slight crushing of the frontals, fheir outlines cannot 
be traced. Apparently, however, there is little if any indication of a posterior 
expansion such as Brown figures in Paramylodon. 
The malars (Plate 3, fig. 7) or jugal bones are complete and separate. Proba- 
bly they were but loosely articulated with the maxillaries. The upper anterior 
portion is concavely rounded to form the lower border of the orbit. The ascend- 
ing wing of the bone has a deep notch for the reception of the squamosal process. 
In the South American Mylodon robustus the portion of bone dorsal to the notch 
is produced backward so that the distance from its tip to the point of the notch 
is nearly twice that from the tip of the bone forming the ventral side of the 
notch to the same point. This bone is not described for any of the North Ameri- 
can species nor for Paramylodon, but in our specimen it presents the noteworthy 
difference that the bony wings forming the sides of the notch are of nearly equal 
length, the dorsal only some 10 mm. longer than the ventral portion. The 
descending portion of the malar is similar to that of M. robustus in general form 
but is narrower and longer, with a wider concavity between it and the ascending 
portion. Its anterior margin is also much less bowed out. 
The premawillaries were evidently united, but were only loosely articulated 
with the maxillaries by a short stem which fitted into a deep median cleft between 
them at their anterior end. The lateral wings of the premaxillaries bevel over 
the dorsal surface of the tips of the maxillaries, but are wholly separate from 
them. The cleft for the reception of this articulating stem of the premaxillaries 
extends posteriorly as a broad V for about 31 mm., or nearly one half the dis- 
tance from the tip of the maxillary to the first tooth. It is apparently much 
deeper in the Colorado skull and in Paramylodon, extending nearly to the 
level of the large oval tooth (the second in Mylodon). The greatest median 
length of the premaxillaries is 54 mm., their combined width 96. The tips are 
thickened and slightly concave below as if for aiding the prehensile power of 
the lips, 
