Die Tympanalgegeiid des Säagetierschädcls. 525 



peculiarities witli confidence. The tympanic is exceedingly small, 

 and is but sligiitly inflated into au inconspicuoiis bulla, tbe anterior 

 third of vvhich is quite flat and narrows forward to a point. Therc 

 is no tubulär auditory meatus, the external opening into the bulla 

 beiug a mere hole, but the anterior lip of this openiug is drawn out 

 into a Short process, somewhat as in existing dogs. Behind the bulla 

 is a large rcniforni vaeuity or fossa, of which Lcidy remarks: ,,At 

 first, it appeared to nie as if this fossa had been enclosed with an 

 auditory bulhi and what I have described as tlic latter was a pecu- 

 liarly raodified auditory process'' ('69, p. 33). Several specimens 

 representing both the White River and John Day species of Dapliaemis 

 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 beeame separated from the skull on fos- 

 silization. At the bottom of the fossa (i. e., when the skull is turned 

 with its ventral surface upward) is seen the exposed periotie, or 

 petrosal, which is only partiall}' overlapped and concealed by the 

 tympanic. Such an arrangement is far more primitive than that 

 which is found in any other known member of the canine series, 

 and is not easy to Interpret. A elue to its meaning may, however, 

 be found in the mode of development of the bulla in the reeent 

 Canidae. Here, as is well-known, the structure consists of an anterior 

 membranous and posterior cartilaginous portion, which eventually 

 ossify and coalesce into a Single bulla. Reasoning from this analogy, 

 we may infer that in Daphaetius the bulla was also composed of 

 two portions, but that only the anterior Chamber was ossified, the 

 posterior one remaining cartilaginous. Communication between the 

 two Chambers was provided for by the space which separates the 

 hinder edge of the anterior Chamber from the petrosal. If this 

 interpretatiou be correct, it supplies an interesting confirmation of 

 the results derived from the ontogenetic study of the reeent genera. 

 At all events, it seems much more probable that we have to do here 

 with a primitive rathcr than a degenerate structure« (Scott, 1898''). 

 WiNGE (1895'' bringt Daphaenua denn auch zu seiner Familie der 

 AmpJiictidae (s. S. 512). Scott schließt jedoch, wie aus obigem Zitat 

 hervorgeht, die Möglichkeit nicht aus, daß eine knöcherne Bulla, 

 also ein Entotympauicum, vorhanden gewesen ist, in welchem Falle 

 die Übereinstimmung mit Paradoxurus größer gewesen wäre. 



Bei Cynodictis aus dem Eocän und Oligocän sind beide Teile 

 verknöchert und miteinander verwachsen, aber ihre Grenze ist deut- 



