JVo.1.] COPE ON HOKIZONS OF EXTINCT VEETEBRATA. 43 



The above tables show that the history of mammalian life in the two 

 continents presents many points of resemblance ; but that there is a 

 great difficulty in correlating the epochs represented by the known 

 launte. As regards the two primary divisions, Eocene and Miocene, they 

 have no special raison dJetre, as such faunae as the Tongrian and Oenin- 

 gian are absolutely transitional in their character. More detailed com- 

 parisons of the European and American faunse bring out many relation- 

 ships not displayed by the above tables, and which I will now brieiiy 

 consider. 



In the American Bridger, various genera of ilfesof7onf« represent the 

 few Adapidw of the Parisian, the genus Adains* Cuv. being probably 

 common to the two continents. The American Anaptomorphus, a true 

 Lemur, has been found by M. Filhol in the Phosphorites, and named 

 Necrolemur. The characters of the numerous Carnivora of the Bridger 

 are as yet unknown. The Stypoloplms of the Bridger is perhaps the 

 Prototomus of the Wasatch, and this again has been discovered by M. 

 Filhol t in France; while a very similar, if not the same, genus has been 

 discovered in the Swiss Siderolitic, and named Proviverra. Hywnodon- 

 tidce probably occur in the Bridger. Iv'owhere in Europe do we find the 

 Binocerata and Tillodonta of the Bridger. Palceosyops is also unknown 

 in Europe, but it plays the part in America of the Palceotherium, from 

 which it does not greatly differ in structure. The latter genus is most 

 largely developed in the Parisian, but is also characteristic of the Ton- 

 grian. Hyracliyus is the American LoxModon^ the difference between 

 them being but slight : both are found in France ; the former in the 

 Lower Parisian, the latter in the Phosphorites. Tapirulus\ Gerv. is a 

 genus common to the Bridger and to more than one horizon of the 

 Parisian. The squirrel-like rodents of the Bridger are Hke those of the 

 Parisian, but they are not confined to either epoch. The character which 

 distinguishes the Parisian most widely from the Bridger, besides the 

 absence of the Binocerata and Tillodonta^ is the presence of numerous 

 Selenodont Artiodactyla, as XipJiodon, Ccenotherium, Amphimeryx, Ano- 

 plotherium, etc. These are of primitive type, it is true ; the Anoplotheriidw 

 especially having probably four toes in the very short manus (Uurythermm), 

 including the pollex, and three behind. They also display the character 

 of a fifth crescent of the superior molars, which is wanting in the higher 

 Selenodont types. But even these genera are absent from the Bridger. 

 The ensemble is then, that the latter displays relationships backwards, 

 or to the Suessonian, while the Parisian has a later fades, constituting 

 an approach to the Tongrian and White Eiver. § 



The following table presents the relations of the Bridger fauna suc- 

 cinctly, but it is much less complete than we hope to make it when its 



* Notliarctus is undistinguisliable from Adapis in inferior dental characters. 



tit is described as Cynohycenodon witli two species. 



JGervais, 1850; HelaMes Mvivsh, 1872. 



§ See Ann. Eept, U. S. Geol. Smv. Terrs. 1873, pp. 461-2, wliere tMs view is proposed. 



