166 BULLETIN OF THE 
ment of horns or other protective structures. It equalled in size the largest 
of the modern rhinoceroses, and belongs to a line which is quite distinct from 
that of either Hyracodon, Aceratherium, or Dicerathertum. The great reduc- 
tion of the premolar series separates it from the first, while the retention of 
the full canine-incisor series separates it from the last two lines of descent. 
The skull is remarkably broad and flat, with powerful and widely extended 
zygomatic arches, and a long flattened cranium, surmounted by a strong sagit- 
tal crest. The antorbital or facial region is considerably less than one third 
the entire length of the skull, instead of one half the length, as in Amynodon 
and the modern rhinoceroses, The occiput is low, and projects considerably 
behind the condyle. The small proportions of the facial region and great 
development of the area of attachment for the muscles of the lower jaw are 
respectively in direct relation to the unusual reduction of the premolar series 
and the great size of the molar and canine-incisor series. With these numerous 
peculiarities, the skull still retains a rhinocerotic character and has unmis- 
takable resemblances to that of Amynodon. 
UT ji if. 
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a 3 
Figure 8.— Skull of Metamynodon. Front view. 
The premazillaries are broad and flattened above, and, bulging forwards, con- 
verge into the broad rounded alveolar border. They are quite distinct in the 
median line. The anterior nares, as viewed from in front, are triangular, 
bounded above by the short, flattened obtuse nasals which overlap the inner 
faces of the converging premaxillaries. The nasals viewed from above are 
smooth, short, and broad. The mazillaries form a wide union with the fron- 
tals, and are deeply excavated behind the canines to the large infra-orbital 
foramina. The sutures of the lachrymals cannot be distinguished; they proba- 
bly had a short exposure upon the face. The lachrymal foramen is within the 
orbit. The frontals are very long, extending from the interorbital space to the 
middle line of the cranium. There are no post-orbital processes, but rugose 
supra-orbital processes widely overhanging the orbits, which they completely 
conceal from above. They are separated by a notch from the prominent ant- 
orbital rugosity. The orbits are thus small and deeply enclosed. The malars 
have a faint postorbital process. Their greatest diameter is vertical, but the 
zygomatic processes of the squamosals are twisted, so that they unite with the 
