192 Mr. 8. 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 mvariably 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. Soe. vol. v. p. 345. 
