NOTES ON THE LEA VALLEY.
79
Although a small list, three species, Planorbis carinatus,
P. fontanus and Bithynia leachii, are unrecorded for this part of
the Lea Alluvium though it should be noted that only one other
series has been obtained.2
All these forms are known from the Lea Alluvium at
Walthamstow, and are all univalves, a fact which, taken in
conjunction with their method of occurrence, lends great support
to the view that they did not live where they were found, but
are drifted shells. The gravel beneath the silt is undoubtedly of
Pleistocene age, and, in our opinion, represents a late stage of
that period when the land stood at a slightly higher altitude
relatively to the sea. This third terrace, as it has been called,
is as a rule unfossiliferous, though three species of mammalia
were found in it at Walthamstow in 1869, viz.: Elephas
primigenius, Blum. Bos primigenius Boj. and Cervus Strongylocoris
Owen3. The last named is allied to the Red-deer, though much
larger. In the adjoining Thames Valley a fairly large fauna
has been found in the "Third Terrace." Flint implements
have been found occasionally in the Lea gravel, but all are
much abraded and rolled, and are undoubtedly derived from
higher levels, probably the High Terrace. In all likelihood it
is the higher level gravels that have furnished the materials of
which it is composed.
The water level in the excavations was constant at 8 feet 6
inches from the surface, and great difficulty was experienced in
keeping the excavations dry. The enormous quantity of water
present may be gauged by the fact that from the hole sunk for
the engine bed 10 feet by 14 feet and 14 feet deep, no less than
6,000 gallons per hour were pumped.
We have to tender our best thanks to Mr. A. Kennard for a
knowledge of the sections, and it is entirely owing to the interest
and trouble that he took whilst the excavations were in progress
that this paper owes its existence.
2 A. S. Kinnard and B. B. Woodward "The Post-Pliocene Non-Marine Mollusca of
Essex."—Essex Nat., Vol. x. (1897) p. 91 and Table.
3 Woodward, Henry "The ancient Fauna of Essex," Trans, Essex Field Club,
vol. iii., p. 7