12
ON THE MOLLUSCA OF THE SHELL-MARL
Glacial-drift was reached. On Moor's Farm, half a mile to the east
of that place, the peat predominates, but the shell-marl frequently
occurs. The bed also appears near Roffey Green, Pleshey.
Nearly all the exposures with which I am acquainted are laid
bare by sub-aerial denudation, but, as in this locality the marl
nearly always rests on Glacial-gravel or sand, it often happens that a
subterranean denudation is going on as well. A cutting I had made
in Bushey Leys (a field west of Felstead village) at the base of the
hill, gave the following section :—
Feet. Inches.
Clay (derived probably from the wash of
the Boulder-clay which caps the hill) ... 3 6
Dark chocolate coloured soil ... ... 1 0
Shell-marl............... 0 9
Moist, stony clay, full of roots of trees ...
The above outlines will probably be sufficient to determine the
place of the deposit, and its physical similarity to the exposures
noted by the Geological Survey Memoir to which we have referred.
The principal interest of the beds lies in their fossil-shell remains.
These are entombed in either pure clay, carbonate of lime, or
calcareous peat. In some cases the shells are beautifully preserved,
all the delicate markings, and even the colours, being shewn ; but in
most cases they are exceedingly fragile and fragmentary, and their
examination requires much patience and careful manipulation. As
it often happens that recent specimens are lying in dangerous
contiguity to the fossils—and as it requires much practice, to say the
least, to separate them—only those have been entered in the follow-
ing list which I have actually found in situ. I need scarcely add
that they were all obtained in the parish of Felstead. Mr. J. W.
Taylor, of the Conchological Society, has kindly helped me to
identify many of the species :—
Fossil Mollusca of the Shell-Marl, Felstead.