564 STRATIGRAPHICAL GEOLOGY 



exposed at the surface, as at Latdorf near Bernberg, Egeln near 

 Magdeburg, at Neu Brandenburg, and other places. They 

 are the oldest Tertiary deposits in Germany, and the lowest beds 

 are the sandy clays of Latdorf and Egeln, which contain Ostrea 

 ventilabrum and the other fossils of the Lower Tongrian of 

 Belgium, but the equivalents of the Upper Tongrian are not yet 

 known at those places. 



On the Prussian coast, near Konigsburg, are other deposits of 

 Tongrian age, the lowest being sands with 0. ventilabrum and a 

 bed containing pieces of amber, which is the resin of Pinus 

 succinifera and other conifers. This amber encloses an immense 

 number of insects and arachnids (about 2000 species), with leaves 

 of Pinus, Sequoia, and other coniferse Quercus, Acer, Castanea, 

 Magnolia, Cinnamomum, Palms, and other trees. The overlying 

 beds are sands with layers of lignite. 



Above the Tongrian is the Septarian Clay or Eupelian, which 

 contains the same fossils as that of Belgium, and was clearly 

 formed in a continuation of the same sea. It reaches a thick- 

 ness of nearly 500 feet, but passes eastward into the Stettin sands. 



To the south-west around Mayence on the Rhine is a small basin 

 of Oligocene deposits which must have been formed in a gulf of 

 the Northern Sea. The lower beds are similar to those of Germany 

 and Belgium, but the Septaria Clay passes up into marl and sand 

 with Gyrena semistriala and Potamides plicatus, above which are 

 other sandy beds with P. plicatus, Mytilus Faujasi, and other 

 brackish-water fossils, with some land-shells (Helix, etc.). 



3. Switzerland 



The northern part of Switzerland was also occupied by a sea 

 during Oligocene time which seems to have been connected both 

 with the Southern Sea and with the Gulf of Mayence. The area 

 occupied by Oligocene and Miocene deposits is that of the great 

 lakes between the Alps and the Jura, from Geneva to the Chiem 

 See in Bavaria, a distance of 300 miles. The deposits are like 

 those of Mayence but are much thicker, the upper or Rupelian 

 part alone having a thickness of nearly 1000 feet and presenting 

 the following succession : 



Feet. 



Freshwater beds with Helix Ramondi and Planorbis declivis ~| 

 Marls with Cyrena semistriata and Ostrea cyathula . . 60 



Sandstone with Potamides plicatus and plants 



Septaria Clay (few fossils except Foraminitera) .... 600 

 Sand with Ostrea longirostris, Pectunculus obovatus, Cyrena semi- 

 striata, Potamides troehlearis, etc. ...... 300 



