PLEISTOCENE DEPOSITS 99
*Helix ?nemoralis Linne 1 fragment
*Helicella itala (Linne) 10
*Agriolimax sp. 1
Potomida littoralis (Cuvier) 2 fragments
Unio ?tumidus Philipsson 2 ,,
Anodonta anatina (Linne) 2 ,,
Corbicula fluminalis (Muller) 113 valves
Sphaerium corneum (Linne) 1 ,,
Pisidium amnicum (Muller) 38 ,,
,, clessini Neumayr 3 ,,
,, casertanum (Poli) 1 ,,
,, henslowanum
(Sheppard) 42 ,,
,, moitessierianum
Paladilhe 4
*Land Species.
The freshwater Mollusca indicate the clear calcareous waters
of a freely flowing river. Land snails are very scarce, the least
uncommon species being Helicella itala, a xerophile suggesting
the presence of dry open grassland. All the examples are of
an usual form, being smaller and more contracted than is
normal, and exhibit a distinctly raised spire. This fact was
pointed out by J. P. Johnson in reference to shells of H. itala
from Uphall'(1901, p. 211).
The rediscovery of Potomida [Unio] littoralis is of some
interest. This species was listed for Ilford by Boyd Dawkins
in 1867 (p. 100), but the record was subsequently rejected on
account of the disappearance of original specimens (B. B.
Woodward, 1890, p. 370), and P. littoralis was not found by
later investigators.
The fauna, considered as a whole, indicates a warm-
temperate climate, with annual temperatures above those of
Britain today, and probably milder winters. Belgrandia
marginata, Potomida littoralis and Corbicula fluminalis are
southern forms now unknown in these latitudes, whilst the
extinct Pisidium clessini ( =P. astartoides Sandberger), which