NEOZOIC GEOLOGY IN EUROPE. 487 



(for instance, at a different depth of the sea) without be- 

 coming so much altered as to constitute a new genus. In 

 this connection it is interesting to notice some recent ob- 

 servations of the Abbe Bourgeat upon the Gault of the 

 Jura (21). From a comparison of the faunas at several 

 localities, he finds that the gasteropods and cephalopods 

 flourished best where sandy materials were being laid down ; 

 while lamellibranchs preferred the quieter waters which 

 were depositing" clay. Moreover, the ammonites, as if to 

 enable them to resist the shocks of the material among 

 which they lived, acquired tuberculate shells. 



At the same time it is worthy of note than in the 

 Barremien of Chatillon-en-Diois, Sayn and Lory have 

 found ammonites in a reef deposit among a series of 

 limestones, where the conditions must have been very 

 different (22). 



It is well known that the chalk facies of the Cretaceous 

 system does not spread over the whole of Europe, and that 

 in fact it is confined to the more northerly parts and to 

 Russia. The Upper Cretaceous sea of Northern Europe 

 appears to have extended from the Anglo- Parisian basin 

 eastward between the old central ridge of the Alps on the 

 south, and the ancient rocks of Scandinavia and North 

 Russia on the north. It sent an arm southward through 

 France, which probably united it with the sea of the South 

 of Europe. But even in this northern sea by no means 

 the whole area was occupied by chalk. As we approach 

 the old southern shore, for instance, in Saxony and Bohemia, 

 the Upper Cretaceous loses its chalky character and be- 

 comes sandy. Within the Alps themselves there are a 

 number of small areas of Cretaceous deposits of a still more 

 littoral character. These are known as the Gosau beds, 

 and appear to have been laid down in narrow gulfs, which 

 ran southwards into the old alpine land. The exact cor- 

 relation of these deposits is a matter of considerable 

 difficulty, and has given rise to much discussion. A new 

 examination of the beds in the Gosau valley itself has 

 been undertaken by Kynaston (23). According to him the 

 series is constituted as follows (in descending order) :— 



