THE POST-PLIOCENE NON-MARINE MOLLUSCA OF ESSEX. 97
and Paludestrina marginata are confined to beds of Pleistocene age
in this country ; while, on the other hand, Buliminus obscurus,
and Pupa anglica are not known to occur in any but Holocene
deposits. The presence of some of the larger mammalia,
as the Mammoth and Rhinoceros, is of little use in
determining the exact age, since we now know that they lingered
on in this country into Neolithic times. Judging, however, from
the general facies of the Mollusca, we consider that it
certainly is much later than either Grays or Clacton, and if it be
Pleistocene at all, it belongs to the end of that period.
The record of Paludestrina marginata may, however, be in-
correct, as it is not given in Mr. Brown's list, and the examples
were picked out of his material at the Natural History Museum,
so that it is quite possible that these may have got in by
accident. There is also a possibility that there may have been
two beds, one of Pleistocene and one of Holocene age, and that
the fossils have been mixed together. On examining the shells
a difference in their preservation is to be noted, so that consider-
able doubt must always be thrown on any deductions based on
these specimens. The section is now overgrown, but should it
ever be again opened, it is to be hoped that some competent
observer will, by careful investigation, clear away the difficulties
which at present beset the true interpretation of this deposit.
CLACTON.
The beds at Clacton were first described by Mr. John
Brown, F.G.S., of Stanway, in 1840, and a section given (6), the
figure of which is marked "near Walton." He pointed out the
extraordinary abundance of shells there, and promised a list on a
future occasion. This promise was fulfilled in the following year,
when a list of twenty-five species was given on the authority of
Mr. J. D. C. Sowerby (7), two of which ware described as new,
viz. :—Planorbis helicoides and Helix conoidea. The next and the
most important list was by Mr. S. V. Wood in 1856, and con-
tained fifty-nine names (11). Mr. Wood had worked at Clacton
for some years, and the species are his own determination. In
1866 Mr. S. V. Wood, junr., incidentally noted that the Rev. O.
Fisher had found two species which his father had failed to find,
namely, Paludina lenta and Corbicula fluminalis. Two years later,
in 1868, the Rev. O. Fisher (13) gave a full description of the
beds, but added nothing to our knowledge of the Mollusca. The