RED AND NORWICH CRAGS. 
127 
Here again there seems to be a great tendency for the clay 
beds to thicken towards the east as they sink beneath the sea- 
level. 
This completes the description of the typical Norwich area, 
and it only now remains to speak of the transition district of the 
Bure Valley, where the overlap spoken of in former Chapters 
seems often to lead to the gradual disappearance of the lower 
part of the Norwich Crag, and to the consequent superposition of 
the newer Weybourn Crag immediately upon the Chalk. 
North of Norwich the shelly Crag first reappears in the valley, 
tributary to that of the Bure, at Spixworth, Crostwick, and 
Eackheath. These sections are poor, and principally interesting 
as yielding Tellina halthica. At the lime-kiln north of Eackheath 
Church, the Crag would at first sight be termed unfossiliferous, 
but casts of shells are here and there preserved in thin bands of 
ironstone ; the following is the section :— 
Feet. 
"Pebbly gravel - - . . g 
Black ironstone and indurated sand witb 
ironstone nodules, and casts of Gardium 
Upper Crag -<( edule and LiUorina littorea - . i 
I Yellow sand and gravel - . - 9 
I Laminated sandy clay, disturbed at tojD - 1 to 
LFine buff sand with gravelly seams - - . 
m 
Chalk. ““ 
About three furlongs further north the same beds show shells 
in abundance: here the section is as follows :— 
Feet. 
r 3. Pebbly gravel with shells up to the surface 6 
Upper Crag - 2. Laminated clay . - . „ i 
Ll. Shell bed, sand and gravel - - 2 
Chalk with flints. 
This is one of the most instructive sections in the Bure 
Valley: it exhibits the (occasionally) fossiliferous nature of the 
Pebbly sands and Pebble beds ” (“ Bure Valley Beds ”), and 
shows that in point of structure they cannot be separated from 
the Norwich Crag. 
The following species of shells were collected from this exposure 
of the Crag, by Messrs. S. C. Sothern and H. B. Woodward. 
Littorina littorea - 
Bed 3. 
X 
Bedl. 
X 
Natica catena ? 
. - 
X 
Scalaria groenlandica 
- 
X 
Astarte borealis 
“ 
X 
(very abundant). 
--compressa 
- 
X 
X 
Cardium edule 
- 
X 
X 
Cyprina islandica - 
- 
“ (fragments) 
X 
Mya arenaria 
- 
X 
Mytilus edulis 
. 
- 
X 
Nucula Cobboldiae 
- 
_ 
X 
X 
Tellina obliqua 
- 
- 
X 
X 
—-preetenuis - 
- 
- 
X 
X 
-- halthica 
- 
- 
X 
