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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 Uyracodon, Aceratherium, or Diceratherium. The great reduc- 

 tion of the premolar series separates it from the first, while the retention of 

 the fuU 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. 



TTtC 





Figure 8. — Skull of Metamynodon. Front view. 



The premaxillaries 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 maxillaries 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 



