V.
succeeded by a much newer deposit, the Crag. In-
land, this clay is rarely to be seen in section, except
in railway-cuttings and occasionally in brickyards, but
natural sections occur all along the cliffs and the clay
also crops out to a great extent along the foreshore,
when it is locally known as "platimore." The best
sections are along the Cliffs on either side of Walton
and east of Clacton. It is there much jointed, so as to
break up into small cuboidal pieces, and almost un-
fossiliferous. Some of the included cement-stones
differ from ordinary Septaria, and are full of irregular
vermiform bodies that weather out in relief. At
Clacton-on-Sea are seen great numbers of Septaria
crowded on the surface with organisms resembling
fucoid stems, converted sometimes into iron pyrites,
but more generally into the calcareous material com-
posing the Septaria.
Red Crag. —The only good section of this formation
in Essex is that of the Walton Naze cliff, though
small patches of the series occur inland by Oakley
and Mistley.
The Bed Crag is a sand, mostly coarse-grained and
highly-ferruginous, crowded in general with shells
more or less in fragmentary condition, but at Walton
Naze many are not only perfect, but were evidently
deposited soon after death, the bivalve shells having
frequently both valves united, and the univalves being
perfect at the apex.
The fossils of the Red Crag are of two sorts, those
that lived in the seas of the time, and those derived
from older formations. To the latter belong those
phosphatized bones, teeth, &c, that so often occur at
the very base of the deposit, as well as various shells
from the older Coralline Crag. The shells of the Red
Crag point as a rule to shallow-water conditions, and it
would seem that the sea was not wholly free from
floating ice.
The Walton Crag is destitute of those derivative
Coralline Crag shells, that so largely contribute to
make up the mass of the Red Crag in Suffolk.
In 1874, Mr. S. V. Wood (sen.) remarks that "the
only part of the Red Crag which is genuine and free
from derivations, is that of Walton Naze."* In the
same work he gives the following table of the distribu-
tion in space of the Walton shells, after rejecting
doubtful and derivate species:—†
Species of Mollusca in the Walton Naze (or older) Red Crag 148
British and not Mediterranean species.................. 13
„ ,, Mediterranean ............................ 61
Mediterranean and not British.......................... 14
Neither British nor Mediterranean species .............. 10
Species not known living............................... 50
* Supplement to the Crag Mollusca, p. 198, Palaeonto-
graphical Society, 1874.
† Ibid, p. 219.