File:The Quarterly journal of the Geological Society of London (12736400814).jpg

THE CORA.LLIAN ROCKS OJF ENGLAND.
307
In the first of these quarries (fig.
7) we have at the top about six leet
of magnificent Rag, the massive
portions growing in lenticular
masses with bases not horizontal,
and the intermediate spaces filled
to a large extent with Thecosmilice.
The reef-corals hero are in a
more perfect state of preserva-
tion than in any locality we
know of, and leave little to be
desired. Beneath the Rag is
the uppermost bed of the Lower
Calcareous Grit, a very remark-
able rock, composed of very sharp
fawn-coloured sand in a calca-
reous matrix, and containing
nodules surrounding Ammonites
cordatus, or enclosing a nest of
shells in which Gylindrites Luidii
is abundant. It also contains
Natica cli/tia, Gervillia avicu-
loides, Ostrea solitaria, and Serpula
tricarinata, and is the uppermost
fossiliferous zone of this portion
of the series. It is irregular
in the same quarry, and is pos-
sibly only a ^modification of the
sands below, as, where it thins
out and is only to be traced
just beneath the Coral Rag, the
sand contains similar nodules
here and there. The whole is
underlain by a strong bed of
Calcareous Grit, five feet in
thickness, with Natica marcha-
mensis, Cylindrites Luidii, and
Chemnitzia abbreviata, which cor-
responds to the Natica-bed at
Marcham. These beds probably
represent a later period than the
ordinary Lower Calcareous Grit,
approaching that of the Coralline
Oolite.
In the quarry at the Cumnor
cross road we have an equally
remarkable development of the
Coral Rag, but with nothing like
the above-described beds under-
lying it.
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