72 . MEMOIRS OF THE CARNEGIE MUSEUM 



process of the auditory bulla which enclosed the external auditory meatus. The 

 postglenoid process curves slightly forward and overhangs somewhat the glenoid 

 cavity, though not to so great an extent as in the modern wolves. The character 

 of this process is intermediate between that of the modern cats and dogs. The an- 

 terior border of the glenoid cavity is flat as in the dogs rather than depressed as in 

 the cats, so that the articulation of the lower jaw is dog-like in nature rather than 

 feline. 



Leidy and Scott have both described the auditory bulla of Daphoenus as being 

 exceedingly small, though both express some doubt as to the homology of the ele- 

 ments which they have described as auditory bullae. The following quotation from 

 Scott sets forth the chief characters as described by each of these authors. He says : 

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

 other known carnivore. Its principal characters 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 open- 

 ing into the bulla being a mere hole, but the anterior lip of this opening is drawn 

 out into a short process, somewhat as in existing dogs. Behind the bulla is a large 

 reniform vacuit}'' 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.' Several specimens repre- 

 senting both the White River and John Day species of Daphsenus 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 invariably became separated 

 from the skull on fossilization, ..." 



After a careful examination of pur material and after comparing it closely with 

 the skulls of recent dogs, I am convinced that those elements which have been de- 

 scribed by Leidy and Scott as auditory bullae are in fact that portion of the petrosal 

 enclosing the cavity of the internal ear, while in each instance the auditory bulla 

 has been lost, as from the above quotation it will be seen that both these authors 

 had suspected. Not only do the backwardly projecting paroccipitals, and widely 

 separated mastoid and postglenoid processes indicate the presence of a moderately 

 developed if not large auditory bulla, but on the inner portion of the squamosals 

 and external surfaces of the basiphenoid may be seen marks of the sutures by which 

 they were once loosely attached to these bones. Moreover if we remove the audi- 

 tory bulla, as may easily be done, in the skull of any recent dog so as to expose 



