92 THE POST-PLIOCENE NON-MARINE MOLLUSCA OF ESSEX.
The most noteworthy of these is Helix aspersa since this is
the first time we have seen this species apparently in
association with pre-Roman objects in this country. Agriolimax
agrestis and Vivipara contecta are new records for the Holocene
deposits of the London district, though both species are known
from the Pleistocene. The occurrence of Acanthinula lamellata
at Walthamstow must also be noticed, since this is the most
southerly locality in which it has been found. At the present
day its southern limit is Staffordshire.
TILBURY, VICTORIA AND ALBERT DOCKS.
The mollusca obtained from the peat exposed during the
extensive excavations for Docks are the only Essex specimens
from the Thames alluvium which we have seen, the Canning
Town examples belonging in all probability to the Lea Valley.
The sections were referred to and a list of the species given
by Mr. B. B. Woodward (31). The species are twenty-four
in number, and are now either at the Natural History Museum
or in the collection of the Geographical Society.
WITHAM.
In the Geological Survey Memoir on the North-west part of
Essex (18) is a list of seven species of Mollusca from "the post
glacial beds at Witham copied from a manuscript list by the late
Dr. S. P. Woodward," which list is now in the possession of
one of the writers. The examples from which the list was
compiled were collected by Mr. John Brown, F.G.S., of Stanway,
and Mr. French is of opinion (27) that they probably came from
the shell-marl found in the High Street during an excavation for
a sewer. In the Natural History Museum there is a fine series
from this locality some of which are evidently from the "John
Crown collection." On going over them thirty species have
been identified, twenty-four of which are unrecorded, but no
example of Vertigo pygmaea could be found. We have, however,
listed it on the authority of the recorder. Two alterations are
necessary in the nomenclature Pupa palustris is a synonym for
Vertigo antivertigo, while Clausilia rugosa is now called C. bidentata,
The occurrence of Paludestrina ventrosa is noteworthy since it is a
brackish-water form. Pomatias elegans is represented by numerous
examples and its presence furnishes additional proof of the
former abundance of this species in the county.