568 STRATIGRAPHICAL GEOLOGY 



The northern border of this sea passed through Switzerland, the 

 south of Bavaria, Austria, and Southern Eussia. 



Westward this Nummulitic Sea passed by two channels into 

 the western ocean, which occupied the Central Atlantic area ; one 

 of these channels lying through the south of Spain and Morocco, 

 the other through the north of Spain, the Pyrenees, and Aquitaine, 

 leaving Portugal and Central Spain to form a large island. 



Moreover, the Atlantic Sea reached northward as far as the 

 latitude of Cornwall, and a narrow channel of communication was 

 established between it and the Northern Sea along the line of the 

 English Channel. The proofs of this are found in a small outlier 

 of Lutetian limestone lying directly on the Chalk near Orglandes 

 in the Cotentin, in the fact of Lutetian fossils being sometimes 

 washed up on the shore at St. Malo, and in a block of Miliolina 

 limestone dredged up from the floor of the Channel 39 miles south 

 of the Eddystone Rock. 26 



This early English Channel, however, did not remain open very 

 long, for its closure may be inferred from the great contrast 

 between the faunas of the Bracklesham and the Barton Beds. The 

 Bracklesham or Lutetian fauna has a semi-tropical aspect, and a 

 large number of species are restricted to it, while the Bartonian 

 fauna has a greater resemblance to that of the London Clay, the 

 southern types having become extinct. 



The movement which cut off the connection between the 

 Western and Northern Seas seems to have been an uplift of the 

 whole western area, for the Aquitanian channel was also closed 

 and the eastern end of the Aquitanian basin converted into an 

 area of marshes and lagoons. Farther east, however, in the 

 Alpine region and in Northern Italy, the sea seems to have 

 maintained its position. 



With the commencement of Oligocene time a further change 

 took place, consisting principally in the subsidence of Germany, 

 Poland, and Central Russia, thus opening up communication 

 between the Anglo-Gallic Sea and the Asiatic Sea above mentioned, 

 so that many of the same species of shells occur both in Belgium 

 and near Simbirsk in Russia, such as Valuta suturalis, Ostrea flabella, 

 and Astarte Bosqueti. Various minor changes also took place, the 

 sea penetrating into the Central European land by several channels 

 and inlets, in which a variable series of marine, brackish, and 

 freshwater deposits were laid down, while in France some altera- 

 tion of the drainage system led to the formation of several large 

 lakes. 



It seems to have been about the beginning of Oligocene time 

 that certain important physical changes took place in the British 



