106 THE POST-PLIOCENE NON-MARINE MOLLUSCA OF ESSEX.
gratulation that no variety-monger has turned his attention to
the Mollusca now under consideration. The more remarkable
deviations from the type have been noticed under each locality,
it being considered unnecessary to mention the normal varia-
tions.
One previously expressed opinion that Helix hortensis was
unknown from any deposit has proved to be incorrect, since it
occurs at Chignal, Copford, and Clacton. It is, however, very
remarkable that this species, so common at the present time,
should be so rare in a fossil state.
Non-Marine Mollusca from the River Drift, (with the exception of No. 6)
extinct in Britain. The original specimens are in the British Museum.
1.
2.
3.
4.
5.
6.
7.
8.
Unio littoralis, Erith,
Corbicula fluminalis, Crayford.
Pisidium astartoides, Crayford.
P. amnicum, Crayford.
Eulota fruticum, Ilford.
Paludestrina marginata, N.E. London.
The absence of Helix pomatia furnishes additional proof of
the theory that it is post-Roman in its introduction into this
country. Helix aspersa, as we have already mentioned, has now
apparently been recognised from a pre-Roman deposit in the
Lea Valley, and outside our area it has been recorded from a
Neolithic Kitchen Midden at Hastings.