TERTIARY MAMMAL HORIZONS. 19 



regions cannot be compared until the American forms named by 

 Marsh are adequately studied. The Primates have no direct 

 parallels. Among the Pcrissodactyla, PalcBotJicriuni, Palaplo- 

 tlicriuin, and AncJiiloplius have no parallels in America. The 

 Selenodoiit Artiodactyla of the two continents are A\"idely distinct ; 

 the Gypsc selenodont Artiodactyla have no parallels in America. 

 The bunodont Artiodactyla have not yet been carefully compared. 



(6). There are therefore comparati\'ely few direct reasons for 

 considering the Gypsc and Uinta as nearly contemporaneous but 

 there is a substantial indirect reason namel}' that the}^ both 

 closely underly Oligocene Beds in which there suddenly reap- 

 pears a marked community of fauna in the Nearctic and Palsarc- 

 tic regions. In other words the Gypsc bears a relation to the 

 Ronzon similar to that which the Upper Bridger bears to the 

 Upper Uinta and White River. 



The most signiiicant fact is the apparent invasion of the Palae- 

 arctic region in the Upper Eocene by a great variety of Artio- 

 dactyla which mingled with the older ph}'la of France and 

 Germany. Where did these animals come from ? Not from 

 Asia, certainly, because some of them would have found their 

 way also into the Nearctic, probably therefore from Africa or the 

 Ethiopian Rcgioji. 



9. Composite, Imperfectly Stratified Fissure Deposits of 

 Middle Eocene to Middle Oligocene Age 



The most famous of these fissure deposits are those of 

 Quercy, Egerkingen, Mauremont, Fronstetten. 



In the Swiss Jura are the Boliucrzcii, mainly non-calcareous 

 reddish clay nodules with pisolithic iron grains. The sidero- 

 lithic earths, Sidcrolithiqncs, typically at Mauremont, found in 

 Jurassic limestone fissures are so called because they contain 

 grains of iron, imbedded in concretions probably of mineral 

 spring origin, associated with tra\^ertines. A special type of fis- 

 sure deposits, analogous to the above in certain respects are the 

 PJiospiioritcs, typically represented in Quercy but characteristic 

 also of other periods. 



