452 Eaton — John Day FelidcB in Marsh Collection. 



N. debilis. Viewed in profile, the anterior surface of the 

 mandible appears to rise more nearly at a right angle 

 with the horizontal ramus than in the types of N. debilis 

 and N. gomphodus; and this squarely truncated appear- 

 ance of the mandible is increased by the development of 

 a prominent mental rugosity. Labels accompanying 

 this skull show that, at one time, it was provisionally 

 identified as N. gomphodus, at another time as N. debilis. 

 On the whole its indices point to a closer affinity with 

 N. debilis than with N. gomphodus. The skull of Cope's 



Fig. 12. 



Y. P. M. 



N. confertus is but little smaller than No. 10046 ; but as 

 N. confertus is represented only by a very imperfect 

 mandible, a satisfactory comparison of the specimens 

 is impossible. There is, however, a remarkable simi- 

 larity in the form of their mandibular symphyses. In 

 each the symphysis is very short horizontally and extends 

 but little to the rear of the posterior margins of the lower 

 canine teeth. No. 10046 is supposed to have been found 

 in the middle John Day. 



