294 ON THE ZONAL STRATIFICATION OF THE
and knew the market value of teeth and bones, would have-
overlooked such a find.
All speculations as to their fabricators must be very vague
for the present, only the fact remains that these flints, believed
to be worked, do occur in situ on the London Clay, beneath the
undisturbed Red Crag, at Thorington Hall, and Foxhall, and
sundry other places associated with the debris of the nodule
beds ; and it is tentatively suggested that as, prior to the depo-
sition of the Crags due to the tectonic changes alluded to, there is
the negative evidence that East Britain had been a land surface
from Eocene times, these flints antedate the marine fauna
overlying them. As the subject is likely to be much debated,
it is premature to speak with much confidence as to the outcome
of the question. The presence of a very considerable land fauna
seems to lend soms evidence in support of a pre-existent land
surface at this time.
Opinions are divided as to how the erratics came into the
Crag area. Lankester regarded the phosphates as being origin-
ally Eocene, and the whole as being a littoral accumulation
formed by the detritus of the London Clay and Diestien beds,
together with some sub-aerial and fresh-water products. Most
geologists think they are due to tectonic changes operating from
the Diestien stage, whereby these and the Lenhamian ironsands
were upraised, and their contents transferred to a new area by
denudation.
It is still an unsolved problem as to the direction in which
the waters of the Coralline or Gedgravian seas were introduced.
During the long interval between the uprising of the Lenhamim
and Diestien deposits and the era of the Gedgravian Crag
many of the older forms had ceased to exist in this area. The
faunas of the Diestien sea and Coralline (Gedgravian) Crag have
117 species in common, but these are all species still living in
S. European and Atlantic waters, which, as I suggested 40 years
ago, coming from Normandy, cut their way through the uprisen
pre-Crag deposits, and in doing so transported much of the;
debris of the old to the new sea-bed, introducing at the same
time about 300 new molluscs.
We may thus picture the old Eocene land-surface with its
covering of mixed rocks and chalk-flints, the raw material
from which the supposed tools were fabricated, the whole being