18 THIRD SUPPLEMENT TO THE CRAG MOLLUSCA. 



evidence afforded by derivations from beds anterior to that Crag, to a smaller extent also 

 by derivations from earlier beds of Red Crag age, appear briefly to have been these. 



At the incoming of marine conditions over part of England after the long interval of 

 terrestrial conditions which had endured since the elevation and denudation of the 

 Oligocene sea-bed, and when several of the tropical genera of Mollusca characteristic 

 of the older tertiary time still lived in the sea of our latitudes, the older Pliocene 

 submergence seems to have extended from, the north of Belgium, over the south-east of 

 England, and in that way formed a strait, connecting the North Sea with an arm from 

 the Atlantic which extended over Touraine. 1 The evidences of the oldest accumula- 

 tions of this strait which remain in England are probably some sands on the Chalk 

 Downs between Maidstone and Dover, and (I think it likely) also an outspread of shingle 

 along the strait's northern shore, of which patches remain on the Lower Bagshot outliers of 

 South Essex, and of the Isle of Sheppy, 2 and sweep over the edges of some of these on 

 to the uppermost beds of the London Clay there, as well as of a patch of the same 

 shingle crowning the middle part of the London Clay on Shooters Hill, in north-west 

 Kent, and possibly some others on the chalk of North Surrey, near Caterham. 

 Changes took place in the distribution of the land and water of this strait, and the 

 Coralline Crag ensued. Except over a part of Belgium, and (deeply buried under more 

 recent beds) probably a part of Holland also, the oldest beds of this Pliocene Strait 

 have been almost entirely removed by the later action of the sea, and numerous remains 

 of the marine animals, both vertebrate and invertebrate, which were entombed in them 

 have, in consequence, got into the Red Crag, particularly the nodule bed at its base. 

 Remnants of the Coralline Crag, however, remain near each extremity of this Strait, viz. 

 in Normandy near the one, and in Suffolk near the other end, besides a more general 



1 The French geologists still apply the term "Miocene" to the Faluns of Maine et Loire and of 

 Touraine, although these Faluns appear to be coeval with beds in Belgium to which several of the 

 geologists of that country apply the term "Pliocene," insisting that the "Miocene," i.e. the marine 

 equivalent for the terrestrial interval between the " Oligocene " and the oldest " Pliocene," is not repre- 

 sented by any marine deposits there. To avoid as much as possible adding to this confusion, especially as 

 the oldest part of the English Crag the Coralline is clearly "Pliocene," I have avoided in the text the 

 use of the word " Miocene." The beds of Maine et Loire and of Touraine not only contain many shells of 

 the Coralline Crag which do not appear to be survivors from the older Tertiary seas of England and 

 France, but also living British shells, such as Murex erinaceus, which do not appear to have entered 

 British seas until the time of the Red Crag, or, such as Nassa reticulata, even until the Glacial 

 submergence. 



2 See 'Quart. Journ. Geol. Soc.,' vol. 24, p. 464, and bed No. viii, of the plate in vol. 36, p. 457. 

 Prof. Prestwich, in a paper " On the Extension into Essex, Middlesex, and other inland counties, of the 

 Mundesley and Westleton Beds," read before the Brit. Assoc. in 1881, appears to refer the shingle men- 

 tioned in the text as occurring on the Lower Bagshot outliers to the Lower Glacial pebbly sand (No. 6 of 

 the beds described in the "Introduction" to the first Supplement to the Crag Mollusca) ; from which view, 

 as well as from others in the same paper, I differ. My own view of the events which took place during the 

 Newer Pliocene period in England is given in a memoir of which the first part is published in the 36th 

 volume of the 'Quarterly Journal of the Geol. Soc.,' p. 457. 



