218 Mr. Webster on the Strata lying over the Chalk. 



there, and consequently the last marine deposits would be placed 

 immediately upon the lower ones, and would be less easily distin- 

 guished, as is frequently the case in the basin of Paris, where we 

 are informed that the sandstone without shells, which is over the 

 marls belonging to this formation, is placed immediately upon the 

 siliceous limestone of the lower marine formation, on the heights 

 to the east of Melun and of Samoineau ; the gypsum being wanting 

 there. But as it forms the summits of almost all the hills and plateaux 

 where the gypsum beds are found, they form a separation between 

 the upper and lower marine strata, and render their distinction no 

 longer uncertain. In the counties of Suft'olk and Norfolk, there 

 are very extensive beds of marine shells, imbedded chiefly in a 

 ferruginous sand, and lying above the London clay, which have 

 been described under the name of Crag pits. Among the fossils 

 which have been enumerated as belonging to these beds, many 

 agree with those in the upper marine formation in the Paris basin, 

 and others do not appear to differ from the recent shells of the 

 neigh!)Ouring seas. 



Fossil shells agreeing with the recent occur also in many other 

 parts of the kingdom, now considerably removed from the sea, 

 and are often buried under beds of gravel. These probably belong 

 to the last states of the earth, and might serve as a clue to unravel 

 geological mysteries. 



If we depend upon fossils as a principal means of identifying 

 strata, we shall see great reason to believe that the last of our marine 

 depositions are nearly allied to the upper marine formation of the 

 basin of Paris. 



In this stratum in the Isle of Wight I found the following 

 fossils. 



