Eaton — John Day Felidce in Marsh Collection. 449 



the form and size of the masseteric fossa. In N. gompho- 

 dus its inferior margin is separated from the lower 

 border of the horizontal ramus by a wide bar. In A. 

 debilis the fossa extends farther forward and reaches 

 down to the inferior margin of the jaw, which it may 

 follow for some distance." 21 Cranium No. 10045 is in 



Fig. 



Fig. S.—Nimravus debilis (Cope). Cat. No. 10517, Y. P. M. X %• 



many respects better preserved than No. 10517, although 

 the condyles have been lost, and it shows admirably the 

 positions of the basicranial and palatal foramina, and 

 also the delicate tympanic ring of the right side. 



As regards the size of the infracarnassial. exostoses, 

 it may be said that in the mandibles of the three individ- 

 uals, Nos. 10044, 10045, and 10517, these outgrowths are 

 strongly developed. No. 10045 originally possessed four 

 superior premolars on each side, P 1 on the right side 

 being double-rooted. In the mandible of this specimen 

 the first and second premolars have been lost, the only 



21 J. C. Merriam, op. cit., p. 43. 



