174 



University of California Publications. 



[Geology 



mandible. It appears from the figures* that P 4 has but a single 

 posterior cusp. P, is, however, a heavy tooth apparently with 

 two roots and differing much from the corresponding tooth in 

 M. isckyrus. 



Compared with the later maehaerodont forms this species 

 is relatively specialized in the reduction of P,, and the apparent 

 absence of both heel and metaconid from It is relatively 



primitive in lacking a second posterior cusp on P 4 , and in the 

 prominence of the mandibular flange, which is secondarily re- 

 duced in the later sabre-tooths. The abbreviation of the dias- 

 tema, together with the flare of the alveolar borders, and the 

 robustness of the mandible show that this is a comparatively 

 short-jawed type. 



The combination of characters appearing here is peculiar. 

 The stage of development of the mandibular flange suggests an 

 advanced form of Deinctis, such as is seen in the John Day 

 Pogonodon or in the more primitive Hoplophoneus species. 

 The reduction seen in P ;j and in the posterior portion of M x 

 equals or exceeds that in Smilodon and Machaerodus. The 

 character of P 4 is that of Hoplophoneus rather than of the later 

 sabre-tooths. As far as can be judged from the characters 

 present, this species could not consistently be referred to any of 

 the three maehaerodont groups which it most nearly approaches, 

 viz: Hoplophoneus, Machaerodus and Smilodon. It may repre- 

 sent a new subgeneric type, in which a peculiar set of conditions 

 suggested by the shortness and strength of the jaw have made 

 possible the combination of primitive and specialized characters 

 seen here. A knowledge of the cranium may bring out definite 

 relationship to one of the known groups, and I therefore refer to 

 the species tentatively under the more or less comprehensive 

 name of Machaerodus. 



* K. Lydekker. J-'aJeuut. Lndiea, Ser. 10, Vol. 2, PI. 43. 



