INTRODUCTION. XI 
sands, for they neither contain the shell bed z, nor, though sometimes twenty feet thick, 
do they present any traces of the Chillesford clay over them. It is not improbable that 
while the upper part of these sands belong to the Glacial formation, the lower with 
shell seams belong to the Crag, being the result of the silting up of those channels between 
the banks, at the bottom of which it is that the great chalk flints and other erratics 
occur. Accordingly, in the map we have, as the safer course, nowhere over the Red 
Crag area shown the Chillesford beds unless we could detect the Chillesford clay in the 
neighbourhood.* 
Tur FiLuvio-MARINE CoNDITION oF THE CHILLESFORD Beps. 
In the Sections XVI and XVII first discussed, andin that at Aldeby (No. XIV), the 
Chillesford bed is marine; but in all the other sections of the beds, such as those 
shown in Sections VII, IX, X, XI, XII, and XIV, the bed 5’is more or less Fluvio-marine 
in character, and in the cases of Nos. IX, X, and XI, as much so as is the Fluvio-marine 
Crag of Bramerton itself; and, accordingly, the beds shown in the last-mentioned sections 
have always been regarded by collectors as the Fluvio-marine Crag. The sands, however 
(5'), which in these sections underlie the laminated clay (5”), and contain the shelly seam, 
#, are but very few feet in thickness. The more likely view seems to us to be that the 
sites of Sections IX, X, and XI, which were land during the formation of the Red and 
Fluvio-marine Crag, became, by the depression which at Bramerton caused the Fluvio- 
marine conditions to disappear, and the marine bed # to occur, covered by the estuary, and 
received a Fluvio-marine fauna; the clay 5” eventually spreading over all. In some places 
in the valley of the Tese, near Saxlingham, the bed 5’ is in the condition of compact 
pebbles overlain by the clay 5”, which is somewhat thin (see Section XII). ‘This pebbly 
condition of the bed 5’ seems to have extended across from the 'Tese valley to Bungay ; 
for at Ditchingham, near that place, a patch of it full of shells occurs at the edge of the 
Waveney, in the garden of a house a mile north of the line of Section J. It is too small 
to be shown in the map, and is overlain by the Middle Glacial sand. This line of pebbles 
doubtless marked part of the south-western shore of the estuary portion of the Upper 
Crag sea. 
1 While this introduction is passing through the press, the Fluvio-marine Crag has been discovered by 
Mr. W. M. Crowfoot at the base of Dunwich Cliff, having been cleared of the talus covering by the storms 
of the winter of 1871-2; and various Crag shells, inclusive of Cyrena fluminalis, have been obtained by him 
from it. The Crag here consists of a deep red bed with shells, overlain by micaceous sands with threads 
or thin seams of clay, These sands seem to be those intervening between the Fluvio-marine Crag and the 
Chillesford beds, and they have accordingly been represented in the section of this cliff (R) under the same 
shading as the Crag 4. This shading should have been continued in the section to near the southern end 
of the cliff. An irregular line of denudation parts these micaceous sands from the red (or orange) sand 
marked 6? As to the capping beds (10) of this cliff, see note, page xxix. 
