NOTES ON THE CANIDiE OF THE WHITE RIVER OLIGOCENE. 405 



tion of the condylar foramen from the foramen lacerum posterius, etc.; the femur has a 

 third trochanter and the humerus an extremely prominent deltoid ridge ; the feet are 

 plantigrade and pentadactyl and, like those of many of the viverrines, they are supplied 

 with partially retractile and very incompletely hooded claws. In all probability these 

 structural characters also occurred in the ancestral Felince, but what distinguishes even 

 the earliest Machairodonts is the elongation and compression of the upper canines, the 

 reduction in size of the inferior ones and the development of bony flanges from the ven- 

 tral border of the mandible for the protection of the superior tusks. From such begin- 

 nings the sabre-tooth series may be traced, with various divagations and side branches, to 

 the Pleistocene Smilodon, which in all parts of its structure is extraordinarily like Felis, 

 the only important differences consisting in the dentition (which is of similar type) and 

 in the modifications of the skull, which are necessarily correlated with the enormous 

 enlargement of the upper canine tusks. 



Seeing, therefore, that the machairodont series is well-nigh complete and that none 

 of its known members is at all likely to prove ancestral to the true cats, there can be 

 little reasonable doubt that the remarkably close resemblance which we observe between 

 Felis and Smilodon is not directly due to their relationship, but has been independently 

 acquired in the two series and is the outcome of a parallel course of development, con- 

 tinued from the Oligocene to the Pleistocene. If this be true, there can be no a priori 

 ground for denying that the same phenomena may have been repeated in the dogs and 

 that Boule's suggestion concerning the derivation of the alopecoids from Cynodictis may 

 possibly prove to be correct. In this case, however, the final identity of the two series is 

 even more striking than in the cats and Machairodonts ; to verify the suggestion, it will 

 be necessary to recover the missing links of the alopecoid phylogeny and to show that it 

 has followed a course parallel to but independent of that of the thooids. 



Another alternative possibility is that the foxes became separated from the principal 

 canine phylum at a comparatively late date, and that, consequently, Oynodictis and its 

 allies represent but an abortive side-branch from the main stem. That the separation is 

 of considerable antiquity is shown by the parallel arrangement of the two series to which 

 Huxley has called attention. In both wolves and foxes we find species with mierodont 

 and macrodont dentition, with sagittal crests and lyrate sagittal areas, with lobate and 

 non-lobate mandibles. So far, at least, we are almost certainly dealing with indepen- 

 dently acquired characters. From the standpoint of present actual knowledge it is more 

 probable that the separation did not take place before the end of the Miocene than that 

 it had already been accomplished in the Eoceue, though this conclusion involves the 

 admission that Cynodictis had anticipated the foxes in quite a remarkable way. While 

 very far from denying the possibility of such convergence as is implied in Boule's 



