ON A SECTION AT RAYLEIGH.
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outliers of Bagshot Sand in Essex. The old 1-inch map of
H.M. Geological Survey considerably over-estimates the area
of the sands, no attempt having been made to distinguish the
Passage Beds which separate them from the mass of the London
Clay. Several sections between Hadleigh and South Benfleet
reveal 12-15 feet of thin-bedded sands and clays, resting on
London Clay with sparsely fossiliferous Septaria, and succeeded
by a small thickness of Bagshot Sand. A similar section is
to be seen at Little Thundersley Common. It is, however, in
pits about a mile north of Rayleigh Station that the facts are
most clearly displayed.
A large brickyard has been worked for some years past on the
south-east side of the railway line, near Down Hall. When first
examined by the writers in 1922 the pit had been temporarily
abandoned, and the faces were consequently somewhat de-
teriorated. A few feet of black London Clay were to be seen,
followed by typical Passage Beds passing up into Bagshot Sand.
No fossils were found in the clay, but a heap of rotten Septaria
(since removed) yielded some small poorly preserved gastropods
and a few other forms.1 These Septaria were seen to occur
in situ within 4ft. of the junction with the overlying Passage
Beds. Subsequently the brickyard passed into the hands of the
Rayleigh Press Brick and Tile Co., who proposed to excavate the
clay itself, removing the overburden of Passage Beds formerly
used for brickmaking. The ensuing deepening of the pit at once
revealed a greenish, slightly sandy clay, below the stiff black
layer formerly exposed, and many nodules of marcasite, together
with one small specimen of Pholodomya margaritacea J. Sow.,
were obtained. At about the same time the cuttings for the new
Southend road at Kingley Wood (about 2 miles S.S.W. of the
Down Hall Pit) revealed a richly fossiliferous band near the top
of the London Clay. The section was quickly covered up, and
the writers were unable to examine it when clean, but a number
of fossils were obtained from the tipped clay (see list). The
engineer stated that all the fossils came from one thin bed which
was encountered at the base of the cutting, at the highest point
of the road (200ft. O.D.). It became evident that this fossilifer-
ous horizon would be encountered in the deepening of the Down
Hall pit, and the progress of the working was carefully followed
1. Proc. Geol. Assoc., vol. xxxiv. (1923), p. 317.
H