EED AND NORWICH CRAGS. 
118 
The Upper Crag is exposed on the borders of the valleys of 
the Bure and Yare and their tributaries ; in the Bure Valley it 
covers tiie larger extent of ground. 
Shells are most abundant in beds 1 and 2. They are generally 
much comminuted, but sometimes entire and in their natural 
position. The bands of clay (3) have no doubt served in some 
instances to protect the shells from destruction by percolating 
water, for when these occur in the pebbly gravel (4) they are 
generally in the form of casts. 
The impersistence of the shell-beds has been the subject of 
remark by almost every observer. In by far the larger number 
of sections of the Norwich Crag no organic remains have been 
found. In some pits where their former abundance has been 
testified to, they are now rare, or the seam has been entirely 
worked away. While on the other hand, pits at one time yielding 
no shells have now become fossiliferous. Hence considerable 
interest is attached to every pit that is being worked. 
To its occasionally fossiliferous nature the Norwich Crag owes 
the attention it has received. The shells were so early as 1729 
noticed by John Woodward in his celebrated Catalogue, and 
they were subsequently illustrated by Parkinson, William Smith, 
J. and J. De Carle Sowerby. 
The earliest descriptions of the strata are contained in the 
writings of Arderon dating 1746, after which time they were 
not particularly noticed until, in 1823, R. C. Taylor gave a clear 
and excellent description of the beds, and first applied in a definite 
geological sense the term Crag, a word commonly used in Sufiblk 
to designate any shelly sand or gravel. 
Later, in 1833, the beds were described and many of the species 
were figured by Samuel Woodward; and in 1836 Mr. Charles- 
worth proposed the term Mainmaliferous Crag to distinguish the 
Crag beds of Norfolk from the Red and Coralline Crags which he 
had previously separated. The term Norwich Crag was subse¬ 
quently employed by Lyell in 1839.* * * § Thus the terms Mamma- 
liferous or Norwich Crag came into use, and as a rule they were 
taken to include the group of beds here considered as Upper Crag. 
The term Norfolk Crag was employed by John Phillips,t and 
Upper Crag by Mr. Godwin-Austen,{ and Messrs. Wood and 
Harmer.§ 
Of late years the beds and fossils in the principal sections have 
been minutely examined and described, and it has been sought 
to establish divisions that have been made out in the so-called 
typical section at Bramerton, and to correlate divisions in other 
sections with them. 
* Proc. Geol. Soc., vol. iii., p. 126. 
f Rep. Brit. Assoc. 1863, Trans, of Sections, p. 85. 
j Rep. Bi'it. Assoc. 1868 ; Geol. Mag., vol. v., p. 475. (1868.) 
§ Rep. Brit. Assoc, for 1868, Trans, of Sections, p. 80 ; Geol. Mag., vol. v., 
p. 452. (1868.) The name Norwich Crag is not even used by Messrs. Wood and 
Harmer in their map of the Crag District. 
E 60798, 
H 
