92 



ISLAND LIFE. 



[PAET I. 



and even pure sands and sandstones, characterised by the same 

 general types of fossil remains as the chalk itself. These beds 

 imply the vicinity of land, and this is even more clearly proved 

 by the occurrence, both in the Upper and Lower Cretaceous, of 

 deposits containing the remains of land-plants in abundance, 

 indicating a rich and varied flora. 



Now all these facts are totally opposed to the idea of any- 

 thing like oceanic conditions having prevailed in Europe during 

 the Cretaceous period ; but it is quite consistent with the ex- 

 istence of a great Mediterranean sea of considerable depth in 

 its central portions, and occupying, either at one or successive 

 periods, the whole area of the Cretaceous formation. We may 

 also note that the Maestricht beds in Belgium and the Faxoe 

 chalk in Denmark are both highly coralHne, the latter being, 

 in fact, as completely composed of corals as a modern coral- 

 reef ; so that we have here a clear indication of the source 

 whence the white calcareous mud was derived which forms 

 the basis of chalk. If we suppose that during this period the 

 comparatively shallow sea-bottom between Scandinavia and 

 Greenland was elevated, forming a land connection between 

 these countries, the result would be that a la,rge portion of the 

 Gulf Stream would be diverted into the inland European sea, 

 and would bring with it that abundance of Globigerinse, and 

 other Foraminifera, which form such an important constituent 

 of chalk. This sea was probably bordered with islands and 

 coral-reefs, and if no very large rivers flowed into it we should 

 have all the conditions for the production of the true chalk, as 

 well as the other members of the Cretaceous formation. The 

 products of the denudation of its shores and islands would form 

 the various sandstones, marls, and clays, which would be de- 

 posited almost wholly within a few miles of its coasts ; while 

 the great central sea, perhaps at no time more than a few 

 thousand feet deep, would receive only the impalpable mud of 

 the coral-reefs and the constantly falling tests of Forami- 

 nifera. These would imbed and preserve for us the numerous 

 echinoderms, sponges, and moUusca, which lived upon the 

 bottom, the fishes and turtles which swam in its waters, 

 and sometimes the winged reptiles that flew overhead. The 



