276 Bulletin Afnerican Museum of Natural History. [Vol. XIII, 



IV. Progressive and Specific Characters. 



The above and the following characters show probably the 

 main trend of evolution in the Ox^^x-ivA's. \ they are derived from 

 a comparison of Oxycena lupina (Wasatch, Sparnacien) and Pa- 

 triofelis fer ox {BridigQx, Bartonien) ; it is important to note that 

 O. lupina is an exceptionally slender species, some of its Wasatch 

 contemporaries were more robust, whereas P.ferox is an excep- 

 tionally robust species. The differences between these species 

 are therefore partly such as we should expect to find in the com- 

 parison of any slender and robust types, and partly truly pro- 

 gressive for the family. 



Oxycena lupina. 

 Incisors | 



Canines sub-oval. 



Premolars |. 



Molars |. 



First lower molar tuberculo-sectorial ; 

 second ditto sub-sectorial with talo- 

 nid preserving three reduced cusps. 



Second upper molar transverse. 



First upper molar sub-sectorial, with 

 protocone relatively prominent. 



Skull relatively slender. 



Dorsals 13, lumbars 7 = 20 D.L. 



Caudals numerous. 



Limbs, chest, and back slender. 



Lumbars typical with simple zyga- 



pophyses ; small anapophyses on 



L 1-2. 

 Tibia with short cnemial spine. 



Patriofelis ferox. 



? Incisors 



Canines laterally compressed. 



Premolars f. 



Molars \. 



First lower molar reduced, tuberculo- 

 sectorial ; second ditto truly sec- 

 torial with vestigial talonid. 



Ditto absent. 



First upper molar blade-like, sectorial, 

 with protocone reduced and para- 

 and metacones greatly elevated and 

 connate. 



Skull broad and massive. 



Dorsals 14, lumbars 6 = 20 D.L. 



Sacrals 3 ; 2 sacrals uniting with 

 ilium. 



Caudals 28, large chevrons. 



Ditto robust. 



Lumbars, massive, heavy, with ex- 

 tremely revolute zygapophyses ; 

 anapophyses on L 1-4. 



Tibia with elongate cnemial spine. 



Six sternebrae. 



Ribs heavy. 



V. Systematic Revision. 



Family OxycruidcT. Terrestrial or arboreal Creodonts ; strictly carnivorous 

 in habit ; enlarged canines ; second upper molars when present transverse ; 

 powerful sectorials formed of first upper and second lower molars ; incisors. 



