NOTES ON THE CANIDJil OF THE WHITE KlVEK OLIGOCENE. 661 



rated by a wider notch than in Canis. The depression, or fossa, external to the condyle 

 is very- much deeper and more conspicuous than in the modern genus, in consequence of 

 which the condyles project more prominently backward from the occiput than in the 

 modern dogs. The paroccipital processes are short, but quite stout and bluntly pointed ; 

 they project much more strongly backward and less downward than in the living forms, 

 and are less compressed laterally. Another difference from the modern genus consists in 

 the fact that, while in the latter the paroccipital process has quite an extensive sutural 

 contact with the tympanic bulla, in Daphmnus there is no such contact, the minute bulla 

 being widely separated from the process. The direction taken by the paroccipital process 

 in its course is thus evidently not determined by the size of the bulla, for in the John 

 Day genera, Temnocyon, Hypot&mnodon and Cynodesmus, in which the tympanic is greatly 

 inflated, the shape and direction of the paroccipital are the same as in Daphmnus, with 

 its insignificant bulla. A considerable portion of the mastoid is exposed on the surface 

 of the skull, but it is rather lateral than posterior in position, a difference from Canis, in 

 which the mastoid is hardly visible when the skull is viewed from the side. The mastoid 

 process is slightly larger than in the existing genus and is channeled on the inner side 

 by a groove leading to the stylo-mastoid foramen. 



The limits of the basisphenoid are not clearly shown in any of the specimens, but 

 this element appears to have much the same broad and flattened form as in the recent 

 dogs. The presphenoid is long and narrow and, as in the existing species, is almost 

 concealed from view by the close approximation of the palatines and pterygoids along the 

 median line. The ali- and orbito-sphenoids are not well displayed in any of the speci- 

 mens, but so far as they are preserved, they differ little from those seen in the more 

 modern members of the family. 



The auditory bulla of Daphmnus is very remarkable and differs from that of any 

 other known carnivore. Its principal peculiarities were observed and noted by Leidy, but 

 the material at his command was insufficient to enable him to describe these peculiarities 

 with confidence. The tympanic is exceedingly small, and is but slightly inflated into an 

 inconspicuous bulla, the anterior third of which is quite flat and narrows forward to a 

 point. There is no tubular auditory meatus, the external opening into the bulla being a 

 mere hole, but the anterior lip of this opening is drawn out into a short process, some- 

 what as in existing dogs. Behind the bulla is a large reniform vacuity or fossa, of which 

 Leidy remarks : " At first, it appeared to me as if this fossa had been enclosed with an 

 auditory bulla and what I have described as the latter was a peculiarly modified auditory 

 process" ('69, p. 33). Several specimens representing both the White River and John 

 Day species of Daphmnus show that the fossa is normal and was either not enclosed in 

 bone, or, what seems less probable, that the bony capsule was so loosely attached that it 



