62 University of California Publications. [Geology 



In the two genera, common to the John Day and White River, 

 the John Day species are relatively specialized forms. Hoplo- 

 phoneus cerebralis, and the doubtful H. strigidens of the John 

 Day are not less specialized than the White River forms, and in 

 some characters show an advance. Of the Deinictis group the 

 single typical species, D. cyclpps, has more slender superior ca- 

 nines than the White River species, and the mandible is relatively 

 slender. The upper sectorial is characterized by the large size 

 and prominence of the deuterocone. The brain case is said by 

 Cope to be rather large. 



The three deinictids separated as Pogonodon show advance 

 beyond the White River Deinictis in their larger size, heavier ca- 

 nines ; reduced M 1 ; loss of M 2 , of metaconid of M 17 and of deu- 

 terocone of P 4 ; reduced premolars ; and probably in foot struc- 

 ture also, although this is as yet very imperfectly known. 



The remaining forms, which are included in the Nimravus- 

 Archaelurus group, have appeared to represent more primitive 

 types than any of the White River felines, and being the domi- 

 nant type of the John Day fauna, their presence has naturally 

 tended somewhat to unsettle conclusions as to the stage of evolu- 

 tion and age of these beds which have been drawn from other 

 evidence. As has been shown under the discussion of Archae- 

 lurus and Nimravus, the forms of this group, while possessing a 

 somewhat primitive dentition, show in it some marks of advance 

 not seen in the nearest White River forms. Moreover, we do not 

 find associated with this apparently primitive dentition the prim- 

 itive type of extremity which should accompany it if this were 

 an especially low or early stage in the evolution of the group. 

 The limbs are relatively long and slender and indicate develop- 

 ment of speed rather than prehension, as in the hunting leopard. 

 We should therefore expect to find that in Archaelufus, as in the 

 living hunting leopard (Cynaelurus) , specialization of the feet 

 for running, with weaker prehension, would be correlated Avith 

 short canines ; and that the cheek teeth, having more work to per- 

 form in holding and killing prey, would be less reduced, and 

 would be more efficient weapons. 



Compared with the genus Deinictis, which also possessed 

 rather slender limbs with an apparently primitive dentition, 



