PLEISTOCENE GEOLOGY OF THE THAMES VALLEY. 353
Fishes from the Pleistocene of Grays Thurrock.
Acerina vulgaris ? Cuvier.
Esox lucius, Linn.
Leuciscus rutilus, Linn.
,, vulgaris, Flem.
,, erythrophthalmus ? Linn.
Anguilla ? anguilla ? Linn.
All these fishes are characteristically freshwater species
which are living at the present day in the rivers and lakes of
England and Europe.
MOLLUSCA.
In 1897 after a careful examination of all existent material
and a revision of the previously published lists, Mr. B. B.
Woodward and one of us were able to list 49 species from the
Middle Terrace, but of these no less than 18 were unrepresented
in any collection, whilst several other records were rejected for
various reasons. Of these rejected species only one has
rewarded our researches, viz., Clausilia biplicata, first recorded
by S. V. Wood. There can be but little doubt that the record
of Balea perversa is an error, as already suggested by the same
writer, for numerous tops of Clausilia have been found. We
are now able to verify seven records hitherto unrepresented by
extant specimens. The remaining unverified records are left for
what they are worth, and of these no less than nine are on the
authority of S. V. Wood. This collection is now in the Norwich
Museum, and it has been examined by one of us, and these
species are not to be found there. They are all known from
other Pleistocene deposits so that there is no inherent improba-
bility in their occurrence, but we venture to think that no
reliance can be placed on them. We have found forty-five
species, of which ten are new records. There are four species
known from Grays which we failed to find, whilst twelve
recorded forms are still absent.
Agriolimax agrestis, Linn. This form is represented by
numerous examples not only in our collection but also in the
Natural History Museum. These latter examples were collected
by Mr. Pickering and presented by him to the Geologists