116 
RED AND NORWICH CRAGS. 
at Thorpe near Norwich, many specimens oi Pecten opercularis 
and Tellina crassa. 
The upper bed at Hramerton has been correlated with the 
seam of shells at Brundall, and with the Crag at Aldeby, 
Horstead, and Burgh near Aylsham. But the Crag of Horstead, 
Coltishall, Burgh, and that also of Belaugh (“ Bure Valley Beds ”) 
is regarded by Messrs. Wood and Harmer as fluvio-marine in 
character.* Hence the application of the term fluvio-marine to 
the lower bed at Bramerton is as ambiguous as it is unnecessary, 
for as Mr. Goodwin-Austen has remarked, ‘Ghe fluvio-marine 
portions of the Norwich Crag are simply the indications of the 
places where rivers discharged into the sea/’t 
Moreover from tlie fact that there is no hard line between the 
divisions made out at Bramerton, and that they are there con¬ 
nected by occasional shells through the intervening sand, there 
is nothing to show that the equivalent of this sand may not 
elsewhere be represented by a mass of shells. It cannot be said 
positively that the shell beds at Aldeby, Brimdall, and Coltishall 
were formed precisely at the time when the uppermost Crag of 
Bramerton was laid down. 
Comparisons have been usually based on the so-called typical 
section at Bramerton, where the uppermost zone shows the com¬ 
parative abundance of the slightly deeper-water and more boreal 
forms, suggesting slow submergence attended by gradual altera¬ 
tions in the climatic conditions. Trifling indeed would be the 
alterations, for in number of boreal species the lower crag furnishes 
a larger list than the upper crag. The lower bed is conspicuous 
for the abundance of littoral shells. 
The chief fossiliferous localities are Thorpe, Postwick, Bra¬ 
merton, Whitlingham, and Brundall, in the Yare Valley; and 
Wroxham, Belaugh, and Coltishall, in the Bure Valley. To these 
may be added several other names of places now or formerly 
fossiliferous, Attlebridge and Catton, in the Wensum Valley ; 
Hamlington, Little Plumstead, Kirby Bedon, Trovvse, Arminghall, 
Lakenham, Shotteshani, Forncett, Newton Flotraan, Stoke Holy 
Cross, and Saxlingham Nethergate, in the valley of the Yare and 
its tributaries; Salhouse, Kackheath, Crostwick, Spixworth, 
Horstead, Stratton Strawless, Marsham, and Aylsham in the 
Bure Valley. 
When we come to study the shells in the several beds of Crag, 
even those acknowledged to be on the same horizon, we find that 
they vary not only in the abundance of particular forms, but also 
in the number of different species, indicating perhaps slightly 
varying depths of water or diversities in the sea-bed, that in¬ 
fluenced their distribution. At Brundall Station, for instance, 
Nucula Cobboldicc is specially abundant. At Brundall Church, 
in a bed distinctly on the same horizon, this shell is rare, and 
perfect valves of Cyprina islandica are met with in profusion. 
* Supp. to Crag Mollusca, p. 112 (1872) ; GeoL Mag., vol. v., p. 452 (1868). 
f Quart. Journ. GeoL Soc., vol. vii., p. 129. (1849.) 
