OBSERVATIONS. 19 



outspread in Belgium. By the gradual emergence of this strait the sea in Belgium and 

 East Anglia, at the time represented by the Red Crag, i.e. the commencement of the 

 Newer Pliocene period, had become separated by land from that in Normandy, but the 

 molluscan remains which it has left in the latter country closely agree with those of the 

 older portions of the Red Crag of East Anglia. 1 One of the results of this separation 

 seems to have been to cause, on the English Coast of the North Sea, a great rise and fall 

 of the tide over a very shallow and flat bottom. As this tide surged round the low 

 island of Coralline Crag at Sutton, and also round the peninsula of the same Crag formed 

 by the parishes of Sudbourn, Orford, and Aldboro' (the rest of the Coralline Crag, 

 with some small exception, having been destroyed either during emergence by the sea 

 which deposited it or by the inroad of the Red Crag water), it carried from that Crag a large 

 quantity of its Molluscan remains which thus became mixed with the remains of the 

 Mollusca then living in this sea, so that the banks of Red Crag, which were then 

 accumulating in South Suffolk, became full of such derivatives, while the bed at Walton, 

 being more distant from that island and peninsula, was left almost entirely destitute of 

 organisms of this extraneous origin. 



Eormed under these conditions, and accumulated as banks or foreshores between 

 high and low-water mark, as their peculiarly continuous highly oblique bedding attests, 

 the marine beds of the Red Crag (with the exception of the latest or Chillesford beds of 

 that formation, which accumulated during a slight depression of the area at the close 

 of the Crag,) were continuously undergoing destruction and reaccumulation ; and succes- 

 sive accumulations of them, formed between tide marks, may be seen in some sections laid 

 up at the foreshore angle of bedding, one upon another. Thus the changes in the 

 molluscan life of the North Sea, which from the approach of the glacial period were 

 taking place during the Red Crag, have become obscured by the circumstance that the 

 remains of mollusca which had died out (in that sea at least) were, in consequence of the 

 destruction of these older banks, and the reaccumulation of the material of them in new 

 banks of the same character and mode of deposit, mixed up with those of the mollusca 

 still surviving there, and of some new forms which the change of climate, and probably 

 distant geographical changes also, were bringing in ; this mixed accumulation being 

 further complicated by the introduction of molluscan remains from the Coralline Crag 

 and still older formations. 



1 See ' Etude Geologique stir les Terrains Cretaces et Tertiares du Cotentin,' par. MM. Yielkrd and 

 Dollfus, Caen, 1875, pp. 148 — 163. The material of these beds of the Cotentin referable to the Coralline 

 Crag {Cowjlomirat d tirebratules),o( which Mr. Harmer brought me some from St. Georges de Bohou,near 

 Carentan, appears undistinguishable, both in mineral character and included organisms, from the Upper 

 Beds of the Coralline Crag, at Sudbourn. 



