4
The coast-line of the Coralline Crag sea was probably
parallel to, and perhaps only a mile or two westwards of, the
points mentioned, that is within 10 miles of the existing sea-
board. To the southwest, it presumably crossed Essex, Surrey,
and Hampshire. Kent and Sussex were then part of the
Continent, and the site of Stratford may have been in mid-tide-
way of the English Channel of that period.
No analyses seem to have been published, but there is a
considerable thickness of the formation in which all but a trifling
percentage of the mass is carbonate of lime of organic origin.
11.—THE RED CRAG.
The upper division of the Crag series is so generally stained
to a deep red colour by oxide of iron, that it is almost everywhere
known as the Red Crag, although some authors, who fail to
recognise the continuity of the deposit under slightly-varying
conditions (affecting chiefly the animal forms embedded at differ-
ent points), prefer to separate the Crag of the northern half of
Suffolk, together with that of Norfolk, under the name of
Norwich Crag (to which the only objection is that it is un-
necessary), or of Fluviomarine Crag, on the slender basis of the
very occasional occurrence therein of freshwater shells, which
have also been found in the unquestioned Red Crag of southern
Suffolk, although even more rarely. The term Fluviomarine has
as a technical name the further disadvantage, that it is equally
applicable to the Crag-like Lower Glacial beds of the Bure
Valley, which were long regarded as a part of the Crag series.
The Red Crag has a wider range than the Coralline, over-
lying and surrounding it, and extending far inland, to Thaxted,
Sudbury, Hadleigh, Ipswich, and thence northward by Eye to
Weybourne on the coast of Norfolk. This is the shelly bed so
well known to every collector on Walton-Naze, Felixstowe, and
Bawdsey Cliffs, and in the so-called "coprolite" pits inland
between Ipswich, Woodbridge, and Orford. It is the deposit of
a shallow, turbulent sea, with shifting banks of sand and shells,
so that the result is a bed of more or less shelly sand, 120ft. thick
in places, and many miles in width, even without allowance for
what may have been destroyed or buried out of sight in later
periods.
But between the formation of the Red Crag and that of the
Coralline Crag that preceded it, there was a considerable period,
during which the bed of the sea was raised until the Coralline