Eaton — John Day Felidce in Marsh Collection. 433 



teeth lias been relatively earlier in the fossil skull, for 

 here the permanent cheek dentition is nearly or quite 

 complete, while in the recent skull the upper deciduous 

 carnassials and all the lower deciduous cheek-teeth are 

 still in place and functional, although, on each side, the 

 principal cusp of P 3 has just appeared, and the crowns 

 of P 4 and M 1 have protruded to about half their height. 

 If preferred, the cheek-teeth may be taken as the basis 

 of comparison, in which case it would appear that the 

 replacement of the canines was relatively tardier in the 

 fossil skull than in the recent lynx. 



Cranium. — The basal length of the skull, measured 

 between the basion and the probable position of the 

 prosthion, is 167 mm. This shows the skull to be consider- 

 ably shorter than that of Pogonodon davisi where the 

 similar measurement is about 198 mm. Viewed from the 

 side, the general proportions of the skull of P. serruli- 

 dens resemble those of P. davisi more closely than they 

 do those of Nimravus. This is especially noticeable in 

 the low and straight nasal region, and in the frontal 

 profile which rises higher from the base-line in the 

 neighborhood of the bregma than in the region between 

 the postorbital processes. The sagittal crest does not 

 however, rise as high posteriorly in the present species 

 as in P. davisi. 



The maxilla and the jugal, on each side of the skull, 

 contribute to the formation of what may conveniently be 

 termed the anterior zygomatic pedicle. It is believed 

 that the widely varying proportions of this part of the 

 skull will be found of considerable taxonomic value in the 

 extinct Felidse. In certain genera the anterior zygomatic 

 pedicle affords two excellent measurements, namely, 

 a height, taken as the minimum distance between the 

 inferior margin of the orbit and the alveolar margin 

 of the maxilla, and a length, taken as the minimum 

 distance between the external margin of the infra-orbital 

 foramen and the posterior margin of the zygomatic 

 process of the maxilla. By dividing the measured height 

 by the length, and multiplying the quotient by 100, an 

 index is obtained, admirably suited to the comparison of 

 cranial form, since it is entirely independent of actual 

 size. The anterior zygomatic pedicle of Pogonodon 

 serrulidens is considerably higher than long, as it is in 



