Article XXIIL — THE SKULL OF HYPISODUS, THE 

 SMALLEST OF THE ARTIODACTYLA, WITH A 

 REVISION OF THE HYPERTRAGULID^. 



By W. D. Matthew. 



A very well-preserved skull of this tiny Artiodactyl was 

 found by the writer at Pawnee Buttes, northeastern Colorado. 

 In connection with the fragments of the skeleton already de- 

 scribed from the same region, it gives a fairly complete idea of 

 the characters. 



The animal was not larger than a ' cottontail ' rabbit. The 

 orbits are remarkably large, as are likewise the tympanic 

 bullae. The tip of the muzzle is unfortunately missing, but 

 enough is preserved to show that it was slender and short. 

 The whole skull is distinctly more brachycephalic than in any 

 other White River selenodont — more so, indeed, than in any 

 of the modern Cervidae or Antilopidae with which I have com- 

 pared it. The molar dentition consists of five teeth in each 

 jaw, p| — m|; p| is present in young individuals and repre- 



Fig. I. Hypisodus minimus Cope. Skull, x f No. 0354- White River (Cedar 

 Creek Beds), Pawnee Buttes, Colorado. 



sented by an alveolus in the older animals. A considerable 

 diastema is in front of this alveolus in the upper jaw, and 



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