230 NEOZOIC TIME. [CHAP. XI. 



paring his map of the Parisian epoch, 1 that no communica- 

 tion existed between the two basins except at the time of 

 the Numm. Icevigata zone. 



Whatever conclusion may eventually be formed as to 

 the emergence or submergence of the axis of Artois during 

 the time of the Calcaire Grossier, it is very probable that 

 it and the Wealden area were upheaved at the close of 

 this epoch. 2 



Such a view is confirmed to a certain extent by the close 

 correspondence which exists between the succession of the 

 higher Eocenes in the basins of London and Flanders ; 

 the " sables chamois " of the latter answer to our Upper 

 Bagshot Sands, and M. Ortlieb 3 thinks that these sands 

 were formed against the slopes of rising ground at the 

 time when the Upper Eocenes were being accumulated in 

 the Paris basin. The abundance of flint pebbles in the 

 Upper Bagshots also proves that Chalk was somewhere 

 exposed to erosion. 



.It is possible, however, that the elevation was greatest 

 over the area of the Ardennes on the one hand, and over 

 the Wealden dome on the other, so that for a time the 

 two seas only communicated along the tract indicated by 

 Professor G-osselet. 



However this may be, it is certain that central France 

 was raised above water at this time, and that the southern 

 sea was forced to retreat, so that the Anglo-French area 

 again became subsidiary to the northern province ; many 

 of the southern species of molluscs would be killed off by 

 the consequent refrigeration of the water, and their places 

 would be taken by northern species, and this seems almost 



1 " Esquisse Geol. du Nord de France," p. 321, and PI. XIII. A. 



3 Both Professor Hebert and Dr. Ch. Barrois are of this opinion : see 

 " Recherches sur les Terr. Cret. Sup.," by the latter, p. 1 78. 



3 " Ann. Soc. Geol. du Nord," t. ii. p. 201 ; see also Barrois, t. iii. 

 p. 84. 



