556 



STKATIGRAPHICAL GEOLOGY 



fauna, differing considerably from that of the typical Eocene 

 strata of England, France, and Belgium, and that it attained a 

 considerable development in Northern Germany. The older 

 classification arranged these beds partly in the Eocene and partly 

 in the Miocene System, but this rendered it necessary to draw a 

 line of separation between the two so-called systems in every area 

 of deposition, and in the midst of a perfectly continuous series. 

 The difficulty of making this separation, and the close connection 

 of the faunas of the groups which were formerly called " Upper 

 Eocene " and " Lower Miocene " respectively, has induced geologists 

 to accept Beyrich's proposal to unite these groups under the name 

 of Oligocene. 



The following table shows the divisions which have been made 

 in the Oligocene Series of England, Belgium, and France : 



B. LIFE OF THE PERIOD 



The Oligocene flora does not differ in any great degree from 

 that of Upper Eocene time ; species of Sequoia are still abundant ; 

 palms are common ; leaves of cinnamons, laurels, figs, camphor- 

 trees, acacias, chestnuts, and other trees occur. 



The invertebrate fauna is not large and is a direct development 

 from the Eocene fauna, the genera being all survivors from the 

 Eocene. Echinoderms were not abundant in our northern seas, 

 but were common in the Mediterranean area, especially forms of the 

 genera Echinolampas, Echinocyamus, and Ccelopleurus. 



Of Vertebrates the Mammalia deserve special attention. A 

 large number of new genera make their appearance in the gypsum 

 beds of Paris, which correspond to our Headon Beds and form the 

 Lower Oligocene of English and German geologists. Prominent 



