CREODONTA. 289 



them Cynohycenodon caylmi and C. minor* Through the courtesy of M. 

 Filhol I am in possession of specimens of the former, and I have examined 

 the types of his descriptions. There can be no doubt of their pertinence 

 to Stypolophus.f S. caylusi differs from S. multicuspis and S. aculeatus in the 

 reduced elevation of the cusps of the first inferior true molar, and the greater 

 obliquity of the superior molars. 



Professor GaudryJ has identified this genus with the Proviverra of 

 Riitimeyer, which was proposed to receive a species ft-om the Swiss Eocene. 

 I have examined casts of Riitimeyer's type, which includes the dentition of 

 both jaws, and which are preserved in the laboratory in charge of Professor 

 Gervais, in the Jardin des Plantes, to whom my acknowledgments are 

 due. I find enough difference to induce me to believe that Proviverra and 

 Stypolophus cannot be united, excepting by the discovery of species which 

 shall show transitional features in the characters. The difi'erence is, that 

 while in Stypoloplms the fourth superior premolar has an internal cusp and 

 an external conical cusp flanked anteriorly and posteriorly by a basal heel, 

 in Proviverra the external part of the crown is a single triangular trenchant 

 cusp, and the internal heel is low, forming with the rest of the base of the 

 crown, a right-angled triangle. This difference is significant, when we recol- 

 lect that this tooth is the homologue of the sectorial in true Carnivora. 



Dr. Leidy has applied the name Sinopa to some flesh-eaters of the 

 Bridger epoch without distinctive generic description. An examination of 

 the typical specimen of the S. vorax, which Dr. Leidy kindly permitted me, 

 shows that it differs from Stypoloplms in the rudimental character of the heel 

 of the last molar, if the specimen is not deceptive. It is otherwise identical 

 in the last four inferior molars. 



Species. I have referred five species of the Wasatch formation to this 

 genus and a fourth provisionally (S. Mans). Three species of the Bridger 

 epoch probably belong to it, which, with the two French species, make a 

 total of ten. They may be distinguished as follows, with the imperfect 

 material at my disposal. The molars measured are those of the inferior 

 series ; in the case of the 8. viverrinus their length is estimated from those 



* Eecherches sur les Phosphorites dii Quercy, 1877, p. 227. 

 tCope, Bull. U. S. Geol. Surv. Terrs., 1879, p. 43. 

 % Enchainements du Monde Animal, 1878, p. 20. 



19 o 



