132 Bulletin American Museum of Natural History. [Vol. XVI, 



these teeth approach the round quadrate shape characteristic 

 of Hycsuarctos. D. gidlcyi may be considered as an aberrant 

 member of the genus Diiiocyoii, but its relationship to the 

 tvpe species is perhaps rather formal than real.' 



The skull (Fig. i) is the most complete one yet described 

 of an Amphicyonine dog. Professor Filhol- has described 

 and figured a skull of .1. Icniaiicnsis, but it was by no means 

 complete. The Texas skull, although crushed, is quite com- 

 plete, and the parts of the skeleton preserved enable us to 

 determine the proportions and general character of this great 

 carnivore. 



The size of the skull equals or exceeds that of any living 

 carnivore of which I can find record. It is longer, wider, and 

 deeper than the largest Ursiis iiian'tiiiiiis skull in our collec- 

 tion, and its measurements slightly exceed those given for 

 the Kadiak bear in length and depth (including the jaw). 

 The crushing of the skull prevents any exact comparison in 

 width; but the Kadiak skull is probably much wider than 

 was that of D. gidlcyi. 



The most striking characters of the skull are the size and 

 depth of the jaw, and the heavy zygomatic arches. The 

 nasal openings are large and cavernous, as in the polar bear, 

 unlike the smaller and more slender muzzle of the lesser bears 

 and of the dogs. The inferior postorbital process is hardly 

 as prominent as in the wolf, much less than in any of the 

 bears. The tympanic bullae are inflated, although of pro- 

 portionately smaller- size than in the wolf. The teeth are 

 larger in proportion to the size of the skull than in the bears , 

 especially the molars, which exceed those of U. maritimns in 

 length and are more than twice as wide. The cranium bears 

 a high crest, as in Amphicyon, giving attachment for the 

 powerful jaw-muscles; and the brain is decidedly smaller 

 than in the modern Ursidae. Compared with Amphicyon 



' Should further study of the American Amphicyons render it advisable to remove 

 D. gidU'vi and the probably nearly allied D. ma;andrinus to a different genus. Cope s 

 name Borophagns may perhaps be used. But as the type of Borophagus is from the 

 Blanco beds it would be desirable to know more than we do at present about the Blanco 

 Amphicyons before making any such change. All that can be said at present is that 

 there were two or more species of the group in this horizon, of unknown dental formula. 



- Arch. Mus. Lyons, III, 1883, pi. i, figs. 3-5. 



