The Ancient Fauna of Essex. 27
perhaps have fallen a prey on that very spot to wild beasts,
and afterwards the skull may have been cleared of animal
matter by predaceous insects. It seems incredible that such
a large number of adult snails could have been washed in by
water through so small an aperture, and that one the sole
opening into the brain-cavity."14
There is one other point which I would wish briefly to
notice : it is the question of the origin of the brick-earth.
Mr. Whitaker observes (Geol. Surv. Memoir, 'Guide to the
Geology of London and the neighbourhood,' 8vo, 1880,
p. 65):—
"The origin of this brick-earth is rather doubtful; in some
places it seems to be little else than a mixture of rearranged
Lower Tertiary Beds, with barely a trace of bedding; whilst
in others it is a more or less finely-bedded sandy clay, or
clayey sand; on the north it is possible that it may be
allied to the deposits next underlying the Boulder-clay, the
'Middle Glacial' of Mr. S. V. Wood."
From its occurrence in large hollows or in pipes let into
the Chalk, and being also said by Mr. Whitaker to be often
full of flints, and of variable colour from light brown to grey
and red-mottled, there can be little doubt that it may be
classed with the "clay with flints," or the "argile a silex" of
the French geologists. Mr. Whitaker says (op. cit., p. 64) :—
"The greater part of the higher ground of the chalk-
tracts, both on the north-west and south-east, has a covering
of a more or less clayey nature; the upper part of this is
often worked for bricks......From the unworn character
of the contained flints, the surfaces of some of which are as
fresh as if they had come direct from the chalk, we may infer
that the deposit has been formed on the spot where it is now found,
not from materials transported from a distance, but through
the dissolving away of the chalk, of which the pipes give
evidence. By this process the carbonate of lime of the chalk
would be dissolved away, and the insoluble flints and earthy
(aluminous) matters left behind, the last receiving, perhaps,
an addition from any pre-existing clayey deposit that might
occur over the chalk.
13 We may conclude, therefore, that the 'clay with flints'
14 See Appendix 5, p. 70, to Catalogue of the Pleistocene Vertebrata in
the Brady Collection. London, 1874.