190 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. .Mar. 10,
Pupa anglica (W.). Vertigo substriata (W.).
Vertigo palustris (W.E.). Clausilia bidens (W.).
pusilla (W.E.). nigricans ("W.).
edentula (W.E.). Rolphii (W.).
pygmsea (W.). Achatina acicula ? (W.).
angustior (W,). Carychium minimum (W.E.).
alpestris (W.). Acme fusca, and var., reversed (W.).
Freshwater Shells.
Succinea putris (W.E.). Planorbis nitidus (W.).
Pfeifferi (W.E.). albus (W.).
Limneus truncatulus (W.E.). vortex (W.).
pereger (W.). Bithinia tentaculata (W.E.).
palustris (W.E.). ventricosa (W.).
stagnalis ? (W.). Valvata piscinalis (W.E.).
Physa hypnorum (W.). cristata (E.).
Planorbis spirorbis (W.E.). Pisidium obtusale (E.).
contortus (W.). pulchellum (E.).
marginatus (W.). pusillum (W.).
imbricatus (W.). Unio or Anodon, fragments of, ? (W.).
Entomostraca.
Valves of Candona lucens (W.).
In this marl the horn-core and bones of Ox, antlers of Stag, and
bones of Elephant have been met with.
It may be observed that the shell-marl does not appear to be of
much use to the agriculturist as a top-dressing, it having failed to
produce the effects which result from the application of chalk to the
land.
Figures of the two extinct land-shells above-mentioned are given
in the accompanying woodcut, fig. 4.
Fig. 4. — Extinct Shells from the Freshwater Beds at Copford.
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a b c d e
a—c. Helix incamata. d, e. Helix ruderata (magnified).
Overlying the white marl is an unstratified deposit of reddish-
brown clay (No. 1 of the section), containing chalk-nodules, rounded
and angular flints, boulders of greywether and other sandstones,
limestones, conglomerates, and porphyritic rocks. This clay is from
1 to 6 feet thick ; the greatest thickness occurring in the northern
part of the field. To the south it passes over the limit of the marl-
beds, and rests on the yellow bed into which the blue clay or brick-
earth passes. No organic remains have been found in this brown
clay, excepting a molar tooth of a Horse, and this was obtained near
its junction with the white marl.
At the western and northern parts of the field there is a superficial
bed of peat, about 1 foot in thickness, with recent land and fresh-