CRETACEOUS AGE. 



following ages, and which, therefore are characteristic of the 

 Cretaceous age. 



2 That this total number consisted of seven distinct groups, 

 which existed successively during the seven periods of the Cre- 

 taceous age, their remains being deposited in the seven superposed 

 stages which compose the Cretaceous formation. 



3 That each period therefore had its own special fauna, 

 having nothing in common with those of the preceding or suc- 

 ceeding periods. 



4 That the species which, owing to accidental causes or erro- 

 neous designations, have been found in two or more stages, the 

 number of which has been greatly overrated, do not in reality 

 exceed a half per cent, of the total number of species discovered. 



403. When tranquillity had been re- established after the cata- 

 strophe which closed the Jurassic age, the changes which had 

 taken place in the levels of the solid surface of the earth caused the 

 waters to settle into new beds, and gave a modified outline to land 

 and sea. The contours of the seas of this period are now shown 

 by the forms and limits of the Cretaceous strata, subsequently 

 raised above the waters. 



404. The outlines of land and water in "Western and Central 

 Europe, in the Cretaceous age, as sketched by M. Elie de Beau- 

 mont, are shown in the map (fig. 171). 



The three great islands of the Jurassic age which appear in the 

 map (fig. 154), were now connected, and their coast-lines com- 

 pletely changed. The northern part of Belgium was submerged, 

 and Brussels, which in the former age was inland, was now on the 

 coast. Arras, Calais, and Dunkirk, which were on or near the 

 coast, were now at the bottom of a large gulf, in the midst of 

 which was Paris, and at the southern part Tours. The town of 

 Poitiers, which was situate in a strait, was now on the coast of 

 the southern extremity of this gulf, which the reader will readily 

 identify with the Anglo-Parisian basin so often referred to. 

 London and Cambridge were at the bottom of this sea, the shores 

 of which, bending westward, formed a bay, which might be called 

 the gulf of Exeter, that city being at its westward limit. Oxford 

 was on the coast of England, which, after jutting out eastward to 

 a point near the site of Cambridge, turned northwards to 

 Edinburgh. Holland and a large part of Prussia and Poland, 

 including the cities of Amsterdam, Hamburg, Berlin, and 

 Warsaw, were altogether submerged. 



An isthmus connected the central tract of France with Brittany, 

 at that time part of a continent, which, extending across the 

 channel, was continued to the extreme north of Scotland, being 

 there probably united with the Hebrides. 



H 2 99 



