NOTES ON" THE CANIDiE OF THE WHITE RIVER OLIGOCENE. 359 



The asymmetry of this phalanx is quite marked : its tibial side is straight, while the 

 fibular border is quite concave, and the dorsal surface is hollowed, or cut away, near the 

 distal end, allowing a retraction of the elates, to a limited extent, as may be readily seen 

 when the second and third phalanges are put together. This asymmetry of the second 

 phalanx is much less conspicuous than in Dhnictis, not to mention the modern felines, 

 but it is, nevertheless, unmistakable and is certainly one of the most surprising features 

 in the whole structure of Daphcenus. 



That an animal with the skull and dentition of a primitive dog should prove to pos- 

 sess even imperfectly retractile claws is not what our previous knowledge of the early 

 carnivores would have led us to expect. So unlooked for was this character, that at first 

 I was strongly inclined to believe that the association of the hind foot shown in PI. XX, 

 Fig. 21, with the skull of D. hartshomianus was an accidental one, and that the pes 

 must belong to some genus of felines or Machairodonts as yet unknown. Fortunately, how- 

 ever, the collection contains a number of other individuals with more or less well-pre- 

 served hind feet, and the agreement among them all is complete. Curiously enough, the 

 characteristic second phalanges are preserved only in connection with the specimen 

 figured, but other specimens have parts of the tarsus, metatarsus, proximal and ungual 

 phalanges, and a comparison of them shows that the reference of this particular hind 

 foot is not open to question. The fact that the pes and the skull were found enclosed 

 in the same block of matrix corroborates this inference, though, of course, such a fact is 

 not of itself entirely conclusive. 



The ungual phalanx is hardly less peculiar than the second, being short, very much 

 compressed laterally, and bluntly pointed ; it is very little clecurved and has a plainly 

 marked groove on the plantar face near the distal end. The narrowness, compression 

 and straightness of this claw are in very decided contrast to the heavy and strongly 

 decurved ungual phalanges of the modern Caniclce, though among the latter there is con- 

 siderable variation in these respects. The articular surface for the second phalanx is 

 much more strongly concave than in Canis, permitting a greater freedom of motion in 

 this joint, as was necessary in order to provide for the retraction of the claw. The sub- 

 ungual process is not so large as in the modern genus and does not project so promi- 

 nently upon the plantar face of the bone, but it is produced much farther proximally, 

 extending beneath the distal end of the second phalanx, when the two are in their nat- 

 ural position. The long hood which envelopes the base of the claw is of about the same 

 size and shape as in Canis, though the space between this hood and the body of the 

 ungual phalanx is narrower. The ungual phalanx of Diniclis is shorter, more compressed, 

 but deeper in the dorso-plantar diameter than in Daphcenus, and has a decidedly larger 

 subungual process, in correlation with the more complete retractility of the claws. The 



A. P. S. — VOL. XIX. 2 T. 



