40 



University of California Publications. [Geology 



specimen of Arehaelurvs with a view to verifying Cope's state- 

 ment regarding this tooth. It was found, however, that the 

 posterior margins are really serrated instead of smooth, Cope 

 having been deceived apparently by the worn surfaces of the 

 tooth. The anterior sides were so much worn that it was not 

 possible to determine their exact form. The evidence available 

 seems to me to indicate that no sufficient generic distinctions are 

 to be obtained in the character of the canines. Though slight 

 differences in the structure of the margins may exist, it is very 

 doubtful whether such variations in general form as may be pres- 

 ent are of more than specific value. 



As to the other generic character used by Cope, namely, that 

 based upon the number of premolars, Cope's type of N. gom- 

 phodus shows no indication of the presence of premolar one in 

 either the upper or the lower jaw, but as this tooth is exceed- 

 ingly small in Archaelurus it is easily conceivable that it would 

 disappear in many cases. In the collection of Professor Thomas 

 Condon, at the University of Oregon, there is a well-preserved 

 feline skull which was studied by Cope and was labeled N. gom- 

 phodus by him. In this individual there are but two inferior 

 premolars. In the specimen as it was studied by Cope there 

 appeared to be only three upper premolars, but more careful 

 preparation of the upper jaw has shown an alveolus for a fourth, 

 or P 1 . In whichever genus this species is placed the dentition 

 of one jaw will represent the other genus. 33 



The differences between the types of Archaelurus and Nim- 

 ravus, or A. clebilis and N. gomphodus, are perhaps most strongly 

 expressed in the lower jaws. In Cope's material, A. debilis 

 was characterized by the presence of a very large exostosis 

 below the molars, while in N. gomphodus this was represented 

 by only a slight swelling of the external alveolar border. Accord- 

 ing to Cope, this thickening was "larger in some specimens than 

 in others. ' ' N. gomphodus was supposed to be further charac- 

 terized by the absence of P L „ absence of an anterior basal tubercle 

 on P 3 , and the failure of the massateric fossa to reach the inferior 

 border of the ramus at any point. 



33 Judging from Condon's figures (The Two Islands, PI. 20, opposite p. 

 124), the superior canine and mandible are of the Archaelurus, type. 



