406 NOTES ON THE CANID^ OF THE WHITE RIVER OLIGOCENE. 



hypothesis, I think it should not be assumed in a. given case except upon the clearest 

 evidence. Whichever of these alternatives be true, it is, in any event, probable that the 

 alopecoids are not of American origin. 



Still a third possible solution of the problem concerning the mutual relationships of 

 the wolves and foxes is that Oynodictis, or some similar form, is the common ancestor of 

 both lines, and that the supposed early thooids, such as Daphcenus and Oynodesmus, are 

 devoid of permanent phylogenetic significance. This is decidedly the least probable of 

 the three alternatives, for the thooids of the American Oligocene and Miocene seem to 

 form a truly connected series, in which Oynodictis has no place. Further, this view 

 involves the assumption that the supposed thooids have independently run a course par- 

 allel to that of the true thooids and thus encounters the very difficulty which it was 

 intended to avoid. The conclusion which we reach is, therefore, that the thooids are 

 probably of American origin and that the alopecoids are a branch which the wolf stem 

 gave off after certain of its representatives had established themselves in the Old World. 



The thooid genealogy itself is by no means free from difficulties. In a former paper 

 ('94), I suggested that the line begins in Daphcenus of the White River, and is con- 

 tinued by the John Day Cynodesmus, but now that we have learned the remarkable char- 

 acters of the skeleton, especially of the limbs and feet, of the former genus, this view no 

 longer appears so simple and natural, and its acceptance carries with it some far-reaching 

 and unexpected consequences. In particular, it might be objected to this view that the 

 peculiar differentiation of the feet in Daphcenus would exclude that form from any place 

 in the direct canine phylum, for it seems a j>ri<>ri unlikely that the dogs should first have 

 acquired the power of retracting the claws and should then have subsequently lost it. 

 Indeed, many morphologists are inclined to deny altogether the possibility of this method 

 of evolution. In the present state of knowledge, however, such a denial is at least prema- 

 ture, and there is a considerable body of evidence which goes to show that it does not 

 properly apply in the case of the canine phylum. 



In the first place, the John Day genus Temnocyon, the osteology of which has been 

 very fully described by Eyerman ('96), appears to be a direct descendant of Daphnusce, 

 with which it agrees in the essentials of structure, though, at the same time, it displays 

 many marked changes and advances. One of the most striking of these changes in the 

 later form is in the great elongation of the limbs and the assumption of a digitigrade 

 gait, both limbs and feet quite closely approximating those of the modern Canidce. Yet 

 even in Temnocyon a reminiscence, as it were, of the partially retractile claws of Daphce- 

 nus may be observed in a certain asymmetry of the second phalanges of both manus and 

 pes, which are slightly excavated on the ulnar and fibular sides respectively. While 

 Daphcenus was a short-limbed, plantigrade or semi-plantigrade form, which, in all 



