6 
CHAPTEE II. 
THE NODULE BEDS, OE BASEMENT BEDS OF THE 
CEAG. 
In Britain, as already pointed out, there is a wide gap between 
the Lower and the Upper Tertiary strata, marked by the dis¬ 
appearance of nearly all the sub-tropical animals and plants of 
the Oligocene period and the incoming of a quite new set, no 
longer sub-tropical though still showing a climate considerably 
warmer than that now found in these latitudes. The break in 
the eastern counties is particularly well marked, for there our oldest 
Pliocene deposits rest directly on the London Clay, and the only 
indication of the former existence of anything of intermediate date 
is found in the phosphate beds, or coprolite beds,"^ as they are 
often wrongly called, which occur at the base both of the Coralline 
and Eed Crags. 
The Nodule Bed’* seems to be nearly co-extensive with the 
Eed Crag, and probably also with the Coralline Crag, though 
often too thin to be of any economic importance. It has been 
extensively worked for phosphatic nodules and phosphatised 
bones, and a large amount of information has been obtained as 
to the origin of the deposits and the character of the included 
fauna. A large proportion of the fossils appears to belong to a 
period somewhat earlier than the Crag, though still truly Pliocene, 
and for this reason, and on account of its peculiar lithological 
character, the Nodule Bed, though really nothing but the base¬ 
ment bed of the overlying Crag, is here described as a separate 
stratum. 
Most of the papers noticing the Nodule Bed treat it merely 
as part of the overlying Crag, but a few that deal more especially 
with the origin of the nodules and the age of their fossils must 
be mentioned here—the others will be referred to in the chapters 
on the Coralline and Eed Crags. 
The first mention of the nodules appears to have been in 1844, 
when Prof. Henslow^ described the concretions from the Eed 
Crag at Felixstow. He came to the conclusion that they were 
of coprolitic origin. He also noticed the occurrence among the 
nodules of the petro-tympanic bones of at least four species of 
Cetaceans (described in an Appendix by Sir E. Gwent). 
* Proc. Geol. Soc., vol. iv. pp. 281-283. Keprinted in Quart. Journ. Geol, 
Soc., vol. i. pp. 35-37. (1845.) 
t Ibid., pp. 283-286. 
