NOTES ON THE CANIDA OF THE WHITE RIVER OLIGOCENE. 407 
probability, was not cursorial in habits, Zemnocyon, 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 juite 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, 
Temnocyon retains recognizable traces of the structure which permits retraction of the 
claws. It is true that Zemnocyon itself isnot in the direct line which leads up to the 
modern Canidae, for the heel of the lower sectorial and the whole of m z 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 Fe/ide. The hunting leopard or cheetah (Cynelurus) has 
acquired something of the proportions and appearance of the wolves, haying 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 Cynelurus with those of Helis, 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 Fe/is. The tar- 
sus, in fact the skeleton of the entire pes, has a canine aspect, and the retractility 
of the claws is very partial and imperfect. Now, there can be little doubt that Cyne- 
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 Daphenus, which has been described in 
the foregoing pages, and which raises more problems than it solves. I am inclined to 
believe, however, that Daphenus 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, sey- 
A. P. S.—VOL. XIX. 2 Z. 
