492 PLIOCENE MOLLUSCA. 



Geological Society, in Fig. 2 of the present volume. There are a few other outliers 

 of the Coralline Crag, as at Boyton, Sutton or Ramsholt, but they are isolated and 

 much smaller. 



In an interesting paper on the Boyton Crag,^ which should not be overlooked, 

 Mr. Bell gives a list of mollusca from that deposit, containing, together with a 

 characteristic Gedgravian fauna, some typical Red Crag species unknown from the 

 latter. Of these, Nassa reticosa and its varieties may be specially mentioned, as 

 well as a single immature specimen of the Waltonian Nepfnnca contrario, now in 

 the York Museum (figured in PI. XXXVII, fig. 3, of my Vol. I). 



Such facts have led Mr. Bell to the conclusion, with which I agree, that the 

 Boyton Crag is of an intermediate age between those of Gedgravo and Walton, 

 still further connecting these deposits. 



In my list of characteristic Waltonian shells given on p. 405, those occurring 

 at Boyton, but not at Sutton or Gedgrave, are indicated by an asterisk (*). 



THE RED CRAG. 

 Waltonian, Newbournian, Butleyan. 



While engaged in the study of the conditions under which the English Crag 

 beds were deposited I was fortunate enough to receive from Dr. J. Lorie, of 

 Utrecht, some valuable papers on the strata met with in deep borings at several 

 localities in different parts of Holland. When shown in section these revealed the 

 interesting fact that the Pliocene beds underlying that country not only attain a 

 tliickness of nearly 500 feet, but that they have been persistently and gradually 

 depressed till, at the furthest point north to which the borings were carried, they 

 were found to reach a depth of more than 1000 feet below their original position. 

 This northerly subsidence seems to have been coincident with an earth-movement 

 of elevation to the south (seo section. Fig. 8) by which the Lenham-Diestien beds 

 have attained a maxinuim height of more than 600 feet above the level of the sea, 

 the line of greatest disturbance, so far as the evidence goes, running at right 

 angles to the strike, from the Straits of Dover to Amsterdam. A compaiison of 

 the mollusca found at different levels in these Dutch borings points to the conclu- 

 sion that those found in the lower part correspond more or less nearly with the 

 characteristic fossils of the Diestien, Casterlien and Scaldisien deposits of Belgium, 

 while those of the upper portion are on the whole of a newer character. For the 

 latter I proposed, in consultation with Dr. Lorie, the term "Amstelien," which, so 

 far as I know, has been generally accepted by Belgian and Dutch geologists. 



The sections (Figs. 1 and 3) show that since the deposition of the Lenham bed 

 and of the ferruginous sandstones of Lou vain and Diest, the south of England has 



^ Journ. Ipswich Field Club, vol. iii, p. 5, 1911. 



