434. Eaton — John Day Felidce in Marsh Collection. 



P. davisi and P. platycopis, the indices of this part of the 

 skull, in these three species, being 120, 148, and 162 

 respectively, and so differing greatly from Nimravus 

 where the length of the pedicle is equal to, or slightly 

 greater than, the height, the corresponding index of 

 N. gomphodus being 100, of N. dehilis 88, and of N. debilis 

 major 92, while in Dinictis cy clops it is 106, and in J). 

 squalidens (No. 8777, A. M. N. H.) it is 107. 



Fig. 3. 



Fig. 3. — Pogonodon serrulidens, sp. nov. Holotype. X %• 



Another remarkable characteristic of Pogonodon 

 serrulidens is the large size of the infra-orbital foramen. 

 The vertical and transverse diameters, taken within the 

 foramen, not at its outlet, are respectively 13 mm. and 

 10 mm. This is a variant toward the typical Hoplophonic 

 form that at once distinguishes the present species from 

 Nimravus. The true significance of very large infra- 

 orbital foramina in certain groups of extinct Felidae is 

 not clear. As the foramina are traversed by important 

 branches of the external carotid artery and trigeminal 

 nerve supplying the lower eyelid, side of the muzzle, 

 and the upper lip, it may ultimately appear that the size 

 of these foramina was directly correlated with the size 

 and mobility of the upper lip in those extinct species that 



