HISTORY OP THE CARNIVORA 



565 



Another doubtfully distinct genus, ^Hemipsalodon, was 

 so closely like, 

 if not identical 

 with, the much 

 better known 

 European fPfer- 

 odon, that the 

 latter may be 

 taken in place 

 of it. \Pterodon 

 was similar in 

 most respects to 

 ^Hycenodon, but 

 distinctly less 

 advanced, and 

 though not the 

 ancestor of the 

 latter, serves to 

 connect it with 

 the older mem- 

 bers of the 

 series. ^Ptero- 

 don did not, so 

 far as we know, 

 penetrate North 

 America south 

 of the Canadian 

 border, occiu"- 

 ring in the lower 

 White River of 

 Alberta. In 

 this genus the 



upper molars re- Fiq. 279. — Lower teeth, right side, of thyanodontids. A, fSi- 



tained a larCP nopa. B, iTHtemrwdon. C, \Pterodon. D, ^Hycenodon. X, Ox- 



ycena. The dotted hne connects the first molar of each, lost 



internal cusp, in Wterodm,. See explanation of Fig. 280. (After Matthew.) 



