314 PROCEEDINGS OF THE ACADEMY OF [1892. 



and simplification of the molar teeth, so that the fiimily definition can 

 be framed only in the most general terms. On tlie other hand, the 

 succession of the genera is so close and the steps of change so 

 gradual, tluit it seems impracticable to subdivide the group unless 

 each genus be given family rank. The connection of this group 

 with the Proviverridce is very close and the line of separation between 

 them arbitrary rather than natural. 



OXY^NAi Cope. 



If Ct P| M|. The incisors are small, except h which is very 

 large and separated by a diastema from the great tusk-like canine. 

 £1 is small and single rooted ; tlie other premolars increase in size 

 and complexity posteriorly ; P2'^"^ 3 have developed the deutero- 

 cone, and P4 is a well developed sectorial, with very large deutero- 

 cone and trenchant tritocone, which with the protocone forms a very 

 effective shearing blade, nearly as large as the first molar. M^^ is the 

 exaggeration of a condition already found in Sinopa and its allies; 

 tbe protocone is somewhat reduced, the para- and metacones very 

 closely approximated and the posterior cutting crest greatly en- 

 larged, forming a sectorial blade. Mj is transversely extended and 

 very short antero-posteriorly ; it appears to consist of a small para- 

 cone and very broad protocone. In the lower jaw pi is one rooted ; 

 p2 and 3 have high protoconids and low, pointed talons ; p* is similar, 

 but larger and the heel is trenchant. The molars consist of a 

 sectorial blade, formed by the enlarged and flattened proto- and 

 paraconids, with a well developed metaconid ; the talon is low, 

 small and basin-like, with continuous margin. The relative size of 

 the molars varies ; in some cases n>i is the larger and in others in^. 



The researches of Cope, and latterly those of Osborn and Wort- 

 man, have given us almost a full account of the skeleton of this 

 curious genus. The skull is quite feline in appearance, with short 

 face, broad and truncate muzzle and large anterior nares, the 

 zygomatic arches are prominent, heavy and moderately long, and 

 the jugal sends up a strong post-orbital process, partially enclosing 

 the orbit. There is a long and prominent sagittal crest and the 

 cranial walls are thick. 



The posterior thoracic and lumbar vertebrse display the creodont 

 type of zygapophyses, and the tail is long and stout. 



1 Rep. Vert. Foss. N. M., U. S. Geog. Surv. W. of 10i)th Mer., 1874, p. 11. 



