192 Mr. S. V. Wood on the Red Crag 



3 or 4 feet thick, formed apparently of the disintegrated mate- 

 rial of the Bryozoon-bank, and destitute of perfect fossils ; this 

 upper bed exhibits indications of having, during the period of its 

 formation, been beached up, somewhat similar to those afforded by 

 the lower stages of the Red Crag, suggesting comparisons with 

 the beach of decomposed coral fringing existing coral shores. 

 Now over this line, this thin and easily denuded upper part re- 

 mains intact, with the Chillesford beds in places resting upon it; 

 and it is almost inconceivable that so tranquil a sea as that de- 

 positing the Chillesford beds could have so evenly removed 

 every trace of Red Crag, and spared this perishable upper por- 

 tion of the Coralline Crag. It is also worthy of note that over 

 this area the lower beds of the Drift sands exhibit peculiar 

 oblique stratification not observable elsewhere, as though this 

 ridge were continued as a shoal in the Drift-sea and produced 

 a quasi-beaching of the sand over it at low water. 



These arguments might be pursued further; but those given, 

 I venture to think, justify me in the view I take that this ridge 

 shut in the Red-Crag bay during the whole of the deposit of the 

 beach Crags. The Chillesford Sands and Clays sweep round 

 the Coralline-Crag ridge, but do not cover every part of it : 

 their absence may be due to denudation taking place at the time 

 when the existing valley-system was formed ; but I am inclined 

 to think that these beds even, although extensively overlapping 

 those of the Red Crag, as well of the fifth as of the beach stages, 

 did not quite cover the Coralline-Crag ridge ; and, although I 

 have not ventured so to represent them in the section, they may 

 possibly be found, in some places, absent between the Drift 

 sands and the Coralline Crag. 



I should have felt much hesitation in thus offering a section 

 so different from that given by Mr. Prestwich, in 1849*, as the 

 result of the investigation by himself, Mr. Austen, Mr. Morris, 

 and Mr. Tylor, but that I learn from Mr, Prestwich that he no 

 longer adheres to the section so given. That section represented 

 the Chillesford beds as resting unconformably on both the Red 

 and Coralline Crags, whereas it appears to me evident that these 

 Chillesford beds are but the continuation of the fifth or water- 

 deposited stage of the Red Crag. 



These Chillesford beds do not occur in the southern part of 

 the Red-Crag area ; the Drift sands there rest invariably on 

 the Red Crag of either the fifth or a beach stage. The line of 

 erosion everywhere dividing the fifth as well as the beach stages 

 of Crag from the overlying sands, shows that these channels, 

 after they had silted up, had become dry land ; and keeping in 

 view, therefore, the very limited thickness of these laminated 

 * Quart. Journ. Geol. Soc. vol. v. p. 345. 



