410 NOTES OST THE CAISTID.E OF THE WHITE RIVER OLIGOCENE. 



It is exceedingly difficult to unravel all this complicated mesh-work of similarities 

 and definitely to distinguish those characters which are due to genetic relationship from 

 those which are merely phenomena of parallelism or convergence. But the important 

 fact remains that in the late Eocene and early Oligocene all of the families of fissipede 

 Carnivora which had then come into existence were very much alike and in all parts of 

 their structure resembled one another much more closely than do their modern repre- 

 sentatives. They are obviously converging back to a common term, and the only ques- 

 tion is what that common term was and whether we are to look for it in the middle or 

 the lower Eocene. It must be reiterated, however, that natural and probable as this con- 

 clusion appears to be, it is only tentative and cannot be demonstrated until the successive 

 phylogenetic stages of each family are much better known than they are at present. 



Summary. 



1. Daphcenus, so named in 1853 by Lcidy and afterwards referred to Amphicyon, is 

 very different from the latter and an entirely distinct genus. 



2. The dental formula is : I 4, C {-, P |, M f ; the premolars are small and sim- 

 ple and are set well apart in the jaws: the sectorials are small and primitive, especially 

 in ? D. Dodgei, and the molars relatively large, most so in D. veins. The dentition is 

 more like that of the creodont family Miacidce than of the typical modern dogs. 



3. The skull is of a very primitive character, with short face, very elongate cranium 

 and high sagittal crest : the cranial cavity is of small capacity and the postorbital con- 

 striction is placed far back of the eyes. Large frontal sinuses are present. 



4. The occiput is low and broad, with very prominent crest; the paroccipital pro- 

 cesses are short and blunt and are widely separated from the tympanic bullae. 



5. The auditory bulla is minute and docs not fill up the fossa, exposing the periotic ; 

 it probably represents only the anterior chamber, the posterior chamber was either not 

 ossified or was very loosely attached, so thai it is lost in all the known specimens. 



6. The cranial foramina differ very little from those of Canis. 



7. The mandible has a short horizontal ramus, varying in its proportions in the 

 different species ; the ascending ramus is low and very broad. 



8. The brain is remarkable for the small size and simple convolutions of the cerebral 

 hemispheres and the large size of the cerebellum and olfactory lobes. 



'•*. The foramina of the atlas differ from those of the recent dogs and resemble those 

 of the cats. 



10. The axis is also of feline character, especially in the shape of the neural spine. 



11. The other cervical vertebra' have more prominent zygapophyses, narrower neu» 

 ral arches and higher neural spines than in Canis, 



