114 
RED AND NORWICH CRAGS. 
Certain lithological characters and certain species of mollusca 
have been taken as guides in forming the subdivisions; but un¬ 
fortunately the numerous observers have not only, as a rule, taken 
different views but have used different terms ; hence there have 
been imported into the subject of the Pliocene deposits of Norfolk 
such a number of local names and synonyms that the literature 
is most confusing to the student. 
Thus in 1865 Dr. J. E. Taylor pointed out the differences in 
the two shell beds exposed in the Crag on Bramerton Common. 
The upper bed contains a larger per-centage of northern mollusca, 
and the most abundant species in it belong to somewhat deeper 
water than those found in the lower division.^ 
Subsequently S. Y. Wood, jun., correlated this upper bed of 
Crag with the Chillesford shell-bed above the Bed Crag, and he 
paralleled a seam of brown clay which almost immediately over- 
lies it, with the Chillesford Clay. The lower bed of Crag at 
Bramerton he regarded as the fluvio-marine equivalent of the 
upper portion of the Red Crag. 
More recently Messrs. Wood and Harmer separated the fos- 
siliferous pebbly sands and gravels of Belaugh, Wroxham, Crost- 
wick, and other places in the Bure Valley from the Norwich 
Crag, regarding the occurrence in them of Tellina halthica 
{solidula) as an indication of their distinct age. And hence these 
pebbly sands came to be regarded by them as Lower Glacial 
Sands,” and (in 1866) to be called the ^^Bure Valley Beds.”t 
Still later Prof. Prestwich divided the beds into Norwich Crag, 
Chillesford Clay, and Westleton Shingle, He included most of 
the fossiliferous beds, whether with or without Tellina halthica^ 
as Norwich Crag. His Westleton Beds are, in the district now 
described, generally equivalent to the Bure Valley Beds.J 
The Norwich Crag has been described as a variable group of 
sands, pebbly gravels, and laminated clays, with occasional seams or 
patches of shells. And this is not only true of the several sections, 
if, for instance, we compare those at Thorpe, Postwick, Bramer¬ 
ton, and Whitlingham, one with another, but it is equally true 
of the sections themselves, for as these are in course of time cut 
back for economic purposes, the sections vary continually, owing 
to the extensive false-bedding. None of the beds are persistent. 
The attempted subdivisions and correlations have been made on 
lithological and palseontological grounds. 
On lithological grounds the Chillesford Clay has been taken as 
an horizon. It has been described as a beautifully laminated clay, 
comprising in reality rapid alternations of clay and sand, both 
very micaceous. At Aldeby, Surlingham, Hartford Bridge, 
South Walshara, Hoveton (near Wroxham Railway Station), 
* Gcol. Mag., vol. viii., p. 314. 
t See Geol. Mag., vol. v., p. 455 (1868) ; vol. vi., p. 232 (1869) ; vol. vii., p. 20 
(1870). Quart. Journ. Geol. Soc., vol. xxii., p. 547 (1866). See also Proc. 
Norivich Geol. Soc., vol. i., p. 50 (1878). 
J Quart. Journ. Geol. Soc., vol. xxvii,, 1871, p. 452. 
