78 NOTES ON THE LEA VALLEY.
differences in the details, the beds varying in thickness in
a distance of a few yards. The general section was as follows:—
1. Surface soil and clay, 3 feet.
2. Carbonaceous silt, 5 to 11 feet.
3. Pleistocene gravel. Thickness unknown.
This section, it will be noted, is almost identical with many
of those exposed in the excavations in the new reservoirs at
Walthamstow, the three divisions being constant.1 The top
layer contained no fossils, and in our opinion represents the
result of the repeated floods of the river since it was confined
within banks and the marshes drained.
The carbonaceous silt was a stiff black clay, full of vegetable
matter, and extremely difficult to wash.
The vegetable remains were so decayed that it was almost
impossible to determine any forms, but remains of the elm were
common. Lenticular patches of moss, often in the condition of
peat, occurred throughout, the patches being sometimes three
feet in diameter, with a maximum thickness of eight inches.
Leaves of the flag (Iris pseudacorus) were very common and well
preserved.
Molluscan remains were scarce, and occurred in patches at
from 7 to 11 feet from the surface.
The only vertebrate fossil was a portion of of the horn core of
a sheep, Ovis aries (Linn).
We have determined the following species of mollusca :—
Hygromia hispida (Linn).
Vallonia pulchella (Mull).
Helix nemoralis (Linn).
Limnaea pereger (Mull).
,, palustris (Mull).
,, truncatula (Mull).
Planorbis umbilicatus, Mull.
,, carinatus, Mull.
„ vortex (Linn).
„ fontanus (Lightf).
Bithynia tentaculata (Linn).
,, leachii (Shepp).
Valvata cristata, Mull.
Vivipara vivipara (Linn).
1 T. V. Holmes, "Geological Notes on the new Reservoirs in the Valley of the Lea; near
Walthamstow."—Essex Naturalist, Vol. xii., pp. 1-16.