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PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. 
blances are more fundamental and significant. The different character of 
the incisors and canines is one of the most striking features of the base- 
view and, in correlation with this, is the reduction of the premaxillaries, 
which form a much smaller portion of the palate than in the last named 
suborder. The muzzle narrows regularly to the anterior end, without the 
broadening forward so characteristic of nearly all the known Toxodonta, 
and the whole palate is relatively shorter, wider and less deeply concave. 
The peculiar form of the posterior nares, which obtains in all of the 
Santa Cruz Toxodonta and Typotheria, with its prominent and divergent 
side-walls, formed by the palatines, pterygoids and alisphenoids, is re- 
peated in the present genus, but the divergence of the walls and conse- 
quent breadth of the opening are even more striking than in Nesodon. 
This base-view also displays the shortening and strong outward curvature 
of the zygomatic arch, reducing the distance between m- and the glenoid 
cavity, as compared with the last named genus. The tympanic bulla 
is much larger than in the contemporary Toxodonta, especially in the 
antero-posterior dimension. The lack of prominence in the region of the 
external auditory meatus and the swollen post-tympanic process is even 
better displayed than in the superior view of the skull, the broadening of 
the cranium external to the paroccipital processes being much less than in 
Adinothevium and Nesodon. The much narrower occiput and the differ- 
ent shape of the condyles are also noteworthy features. 
The condition of the material at my disposal is such that no very 
detailed account of the various elements of the skull can be given, yet a 
certain number of important facts may be made out. The basioccipital 
is quite long and heavy, though narrowing between the large tympanic 
bullae, broadening considerably behind them ; it has a short, but quite 
well-defined ventral keel. The condylar foramina occupy a conspicuous 
position on each side of the posterior expansion and are not hidden by 
the condyles. The latter are rather small, but quite prominent, so as to 
be fully visible in the side-view of the skull. On the ventral side, the 
articular surface of each condyle, near the outer end, is emarginated by a 
deep notch, which is not shown in any of the Santa Cruz Toxodonta, and 
the articular surface is continued over upon the basioccipital in a median, 
shield-shaped area, which is peculiar to the present genus. 
I am unable to determine with certainly the limits of the exoccipitals, 
but they would appear to be much higher dorso-ventrally and to form 
