76 
RED CRAG* 
In 1869 the Rev. O. Fisher* regarded the Norwich Crag and 
the Red Crag as of the same age, as they seem to pass into one 
another ; gave up his opinion that the clay under the Crag at 
Thorpe (near Aldborough) is Chillesford Clay; and remarked 
that the change from Red Crag to Norwich Crag seems to occur 
where the two provinces are partially separated by a ridge of 
Coralline Crag. 
In 1870 Prof. E. Ray Lankester,| from the occurrence of 
dilferent shells in the higher and lower parts of the Red Crag, 
inferred that this deposit represents a considerable time. In 
its earlier period the Red Crag had a fauna not very different 
from that of the Coralline Crag, and with some survivors from 
the still earlier Diestian; in its later period none of these forms 
remained, but boreal forms were added. Contemporaneously with 
the newer Red Crag the Norwich Crag began to be formed, con¬ 
tinuing, Prof. Lankester thought, to be deposited in Norfolk to a 
later time than we have evidence of in Suffolk. 
In the following year Prof. Prestwich contributed a set of 
three papers on the Crag. Of these the secondJ is devoted to 
the Red Crag, which is described as lying in an excavated, area 
in the Coralline Crag, wrapping round the isolated reefs of the 
latter and filling the hollows between [it should be noted that the 
reefs are comparatively small and the hollows of wide extent]. He 
divided it into two only, instead of the five stages of Wood, the 
lower part marked by oblique lamination, and the upper by 
horizontal bedding. The phosphate-bed occurs at the base of the 
lower division, the direction of the lamination of which varies to 
almost all points of the compass, and this false-bedding is most 
general in the upper part of this division. Sometimes beds have 
been eroded before the deposition of those over-laying them. He 
had seen ripple-marks in only one place, Bawdsey Cliff, where 
each of the clayey lamina© of one bed had a ripple-marked surface. 
Another feature sometimes seen there seems, he thought, to show 
that the shoals of the Red Crag sea were sometimes left dry, 
their surfaces fissured by drying, and the cracks filled with the 
matter of the bed next thrown down : while elsewhere a layer has 
been pressed down into those below, causing a wavy structure, 
and the upper part has then been planed down. The introduction 
of the oxide of iron, which colours the beds, seems to have been 
subsequent to their formation, and in one case it has segregated 
in flattened concentric shells, the longer diameter of which may 
be many feet in length. 
Prof. Prestwich further points out that the lower division 
generally abounds in shells, mostly broken, double shells not 
being common ; and that save the old shore at Sutton, no place 
can be easily found where the shells are on the spot where they 
lived. Notwithstanding the great number of shells, the abundant 
* Geol. Mag., vol. vi. p. 142. 
f Quart. Journ. Geol. Soc., vol. xxvi. pp. 493-502. 
X Ibid., vol. xxvii. pp. 325-356. (1871.) 
