NOTES ON THE CANIDvE OF THE WHITE RIVER OLIGOCENE. 407 



probability, was not cursorial in habits, Temnocyon, on the other hand, was undoubt- 

 edly cursorial and probably essentially resembled the modern wolves in appearance and 

 habits. In this change to a digitigrade gait and cursorial habit, it seems quite reasonable 

 to suppose that the mode of using the claws should have been changed likewise, the feet 

 being used almost exclusively for purposes of locomotion and the claws losing their 

 importance as weapons and grasping organs. Under these circumstances the power of 

 retraction would become superfluous and tend to disappear, although, as we have seen, 

 lemnocyon retains recognizable traces of the structure which permits retraction of the 

 claws. It is true that Temnocyon itself is not in the direct line which leads up to the 

 modern Canidce, for the heel of the lower sectorial and the whole of m % have become 

 trenchant through the loss of the internal cusps, a curious specialization ; but, on the 

 other hand, there is no reason to suppose that it differed in any other important respect 

 from its contemporary Cynodesmus, which appears to be a member of the direct phylum. 



In the second place, a similar loss of the power of retracting the claws has almost 

 certainly occurred among the Felidce. The hunting leopard or cheetah (Cyncelurus) has 

 acquired something of the proportions and appearance of the wolves, having very elon- 

 gate limbs and feet and a running gait which is described as quite different from that of 

 the ordinary cats. Comparing the phalanges of Cyncelurus with those of FeKs, some 

 marked differences are at once apparent ; in the lateral digits the second phalanx is 

 quite symmetrical and is not excavated on the ulnar (or fibular) side ; the excavation 

 is distinctly shown only in the third digit and is much less marked in the fourth. The 

 bony hood of the ungual phalanx is much reduced, leaving more than half the length of 

 the phalanx exposed, and the subungual process is much smaller than in Felis. The tar- 

 sus, in fact the skeleton of the entire ])es, has a canine aspect, and the retractility 

 of the claws is very partial and imperfect. Now, there can be little doubt that Cynce- 

 lurus is not the remnant of a very ancient group, given off from the feline stem at a 

 time when the power of retracting the claws had been but partially attained, but that it 

 was derived from ancestors which differed little from Felis. If such a transformation 

 could take place among the cats, there would seem to be no good reason for denying that 

 it might also occur in the dogs. 



Unfortunately, the phylogenetic history of the dogs is not made clearer and more 

 intelligible by reason of the new material of Daphcenus, which has been described in 

 the foregoing pages, and which raises more problems than it solves. I am inclined to 

 believe, however, that Daphcenus should still be given a place in the canine phylum, 

 for the differentiation of its limbs and feet is hardly of that radical kind which would 

 prevent a subsequent change in the trend of development, and its many resemblances 

 to the early Machairodonts are, at least in part, survivals of primitive conditions, sev- 



a. p. s. — vol. xix. 2 z. 



