Vol. 54.] AND THE CORALLINE CRAG. 325 



no two of these four sections are the supposed zones in the same 

 relative position, nor is any reason suggested, except that the 

 London Clay floor was uneven,^ why no beds representing periods 

 B & C should have been deposited in the locality of pit D. The 

 gradient of the surface of the London Clay between pits H and D 

 is, however, only about 1 in 100, so that this explanation seems 

 inadequate. 



Prestwich cited the following genera as specially characteristic 

 of certain zones in the Sutton Crag, namely : — Gyprina^ Pecten, 

 Ml/a, Cardita, Astarte, Anomia, and Venus ; but these are met 

 with not only in all parts of the Coralline, but also and abundantly 

 in every portion of the succeeding E-ed Crag formation. Mr. 

 Burrows, one of the authors of the great work on the Foraminifera 

 of the Crag, just completed,^ speaks of a band containing Oyprina 

 islandica as apparently constant to zone D, and he names a 

 dozen other species of mollusca, smaller forms, which he considers 

 peculiar to Prestwich's zone P, or more abundant in it at Sutton 

 and Gedgrave than at any other horizon. Cyprina islandica 

 has, however, existed in the North Sea, probably without inter- 

 mission, from the Miocene period to the present day, so that its 

 presence or absence at any one spot in the Crag must be accidental ; 

 and it does not seem to me that the other species named by him can 

 be regarded as characteristic even of the whole of the Coralline Crag, 

 still less of any special zone in it. With one or two exceptions, 

 they are Miocene forms, which continued to exist, and even to 

 abound in the Crag area during the subsequent period represented 

 by the Walton bed and the Scaldisien of Belgium, some of them 

 being still found in British seas. It would, however, be equally 

 possible to make up a list of shells which are common at Sutton, 

 and rare or unknown at Gedgrave, or vice versa, but it is a constant 

 feature of the shelly sands that some localities yield a more varied 

 or a somewhat different fauna as compared with others. 



Any resemblance, moreover, which the moUuscan fauna of the 

 beds regarded by Prestwich as zone P at Sutton may bear to those 

 of Gedgrave Hall seems to me to be antagonistic to, rather than in 

 favour of, his views, since the shelly seam at the latter place is 

 within 15 feet of the base of the formation, which at Sudbourne, 

 in the immediate neighbourhood, is 60 feet in thickness. Strati- 

 graphically, therefore, the Gedgrave shell-beds belong to a lower 

 part of the Crag rather than to the supposed upper zone P, to which 

 they have been assigned. 



The evidence upon which I rely for the separation of the Lenham 

 Beds from the Coralline Crag, or which I propose to offer in favour 

 of zones of the Red Crag, is, I submit, of an essentially different 

 character. We find at Lenham Miocene forms which, so far as 

 the evidence goes, had ceased to exist in the Anglo-Belgian basin 

 before the deposition of the Coralline Crag, and have never since 

 reappeared ; while the older Red Crag deposits contain southern 

 and extinct species, which gradually became less abundant in the 



^ Quart. Journ. Geol. Soc. vol. xxvii (1871) p. 116. 



2 Monogr. Palseont. Soc. 1866-97; see also Geol. Mag. 1895, p. 511. 



