scott: ENTELONYCHIA OF THE SANTA CRUZ BEDS. 
261 
dorsal portion of the occiput conceals the condyles from sight in this 
view, as is also the case in Adinotherium , but not in Nesodon. A con- 
spicuous feature, at least in H. segovice , is the notch which emarginates 
the occipital crest on each side and interrupts the connection between the 
crest and the dorsal border of the zygomatic arch, the continuity of which 
with the crest and the elevated position give such a peculiar appearance 
to the skulls of all the Santa Cruz Typotheria and Toxodonta. Another 
striking difference from these suborders is the inferior position and lack 
of prominence of the external auditory meatus and the post-tympanic 
process of the squamosal, so that no trace of them is visible when the 
skull is seen from above, while in the other two suborders the projecting 
tubular meatus and the swollen post-tympanic form the postero-external 
angles of the skull. 
The brain-case, though quite narrow, is more capacious than in Neso- 
don , but contracts rapidly forward to the postorbital constriction, making 
the temporal openings very wide, but quite short, while in Nesodon and 
Adinotherium the antero-posterior diameter much exceeds the transverse. 
The sagittal crest differs much in the two skulls, a difference which is 
obviously in part a matter of age, though possibly both do not belong to 
the same species. In the type of H. segovice , which is quite an old animal 
with well worn teeth, the crest is long and very high and prominent, while 
the young skull (No. 16,014) in which m 5 - is just beginning to come into 
use, it is lower and much shorter, broadening anteriorly into a narrower, 
elongate sagittal area. In neither specimen are there any definite tem- 
poral ridges, extending upon the forehead. The latter is very wide, 
expanding more than in Nesodon , but remarkably short antero-posteriorly, 
which is due to the backward displacement of the nasals. The nasals 
are far shorter and flatter than in the Santa Cruz Toxodonta, making the 
anterior narial opening much larger and of entirely different shape ; in- 
stead of being terminal, it presents more dorsally than anteriorly. The 
dorsal narrowing of the face is very much less marked than in Adino- 
therium or Nesodon and the border of the maxillaries receives a curiously 
fluted appearance from the prominence of the alveoli. The very small 
premaxillaries differ greatly in appearance from the large and massive 
ones of Nesodon. 
Seen from below (PI. XXVIII, fig. 1) the skull presents corresponding 
differences from that of the Santa Cruz Toxodonta, though the resem- 
