56 REPORT—1868. 
The Norwich, or fluvio- marine Crag, the uppermost of Mr. Charlesworth’s classi- 
fication, was for many years the subject of differences of opinion, as to its value and 
distinctness as a division; it had also gradually been made to include much more 
than at first: any bed containing either mammalian and molluscan remains, or even 
an admixture of fresh- and salt-water mollusca, in any part of Suffolk and Norfolk, 
had come to be put down as the equivalent of the Norwich Crag. 
General opinion seems now to have come round to the view which some geolo- 
gists had long since taken. . Writing in 1865, Mr. Searles Wood states, “the Norwich 
Crag is not geologically distinct from the Red, but a fluvio-marine condition of 
the same period.” He establishes this in an analysis of the molluscous fauna, such 
as leaves little doubt as to this point; and the only criticism which is suggested 
is—may it not have been an equivalent of the whole Crag period ? and may not the 
Yar valley have been a tributary to the Crag Sea, during its whole duration as 
such ? 
In Suffolk, the fluvio-marine accumulations at Thorpe, near Aldborough, Wang- 
ford, and Bulcham, are considered by Mr. S. Wood to be of the same age as that 
of Norwich. 
The Forest-bed of Cromer (1824), and some other places, to which Mr. R. C. 
Taylor first called attention, and to which he assigned its true age and position, is 
one of the most interesting points in Norfolk geology ; it is the unmistakeable indi- 
cation of a terrestrial surface, antecedent to the period of the “ glacial-drift ” accu- 
mulations. This old land-surface, at Cromer, is exposed at the sea-level; but it 
extends inland, and has been met with at considerable depths in the offing. 
The arboreal vegetation buried in these beds comprises the Norway spruce, 
Scotch fir, yew, oak, alder,—all of them common North-European trees. 
What the Cromer coast-section demonstrates is, that by process of change 
of level a forestial condition of the surface had been brought down to the sea- 
margin, that the trees had died, and that mud-deposits had formed, partly under 
fresh, partly under brackish water lagoons. 
Subjacent to the “ Forest-bed,” and covering the surface of the Chalk, is a layer . 
of chalk flints; a like accumulation is seen resting on the Chalk in numerous 
other places, as in the sections below this city (Holy Cross, Thorpe, &c.), and are 
all referable to the same agency and period. The flints have been dissolved out of the 
chalk by the action of rain-water, and left im situ; they indicate a long period of 
subaérial conditions; and their formation is coextensive with the whole duration 
of those conditions ; they are therefore of the same period as the “ Forest-bed.” All 
collectors and observers seem now to be agreed upon this, that the Cromer mam- 
malian remains are referable to this particular surface. 
B. GuLaActaL. 
Moye recently the Norwich sections have been subjected to a closer examina- 
tion; and according to Mr. J. E. Taylor (1867) these admit of a twofold division : 
the upper is a coarse and rubbly accumulation, with well-rounded pebbles of 
flint; the lower consists of finer sands. A band of white cross-bedded sand inter- 
venes. Such a change in the character of successive beds would not, by itself, 
have been of much importance; but zoologically the differences they present are 
much more significant. 
The fresh- and brackish-water forms, which long since gave the Norwich Crag 
its fluvio-marine character, occur only in the lower division ; in this, too, the pro- 
portion of littoral species of marine shells is greater ; and here also are found all 
those forms which are supposed to be extinct. 
The upper division has its peculiar forms, such as Modiola modiolus, Astarte 
compressa, A. sulcata, A. elliptica. Other shells are more abundant which in the 
lower are scarce; here they occur as if in their “ life-zone,” instead of as single 
valves, worn and broken—such as Tellina obliqua, Astarte borealis, Venus fasciata, 
Cardium Grenlandicum, Cyprina Islandica, Rhynchonella psittacea. 
It is only in respect of one shell (TZellina obliqua) that the forms of the upper 
division have not been recognized as living; and with respect to distribution, the 
northern facies of the upper assemblage is more strongly marked than that of the 
lower lastly, they indicate a somewhat greater depth of water. 
