Primaeval Man in the Valley of the Lea. 119
the "floor" above and those found from 20 to 30 ft. beneath
the surface. The "Palaeolithic Floor" on fig. 8, if present,
would be just above the horizontal bands of stratification, but
the "trail" at this spot has swept it away; it, however,
occurs in a perfect state a few yards off. Beginning at the
top, the reference-letter, r, is humus; q, mud belonging
to the "trail"; p, a pocket of London-clay; o, "trail";
n, Palaeolithic sand and loam crumpled and disturbed by the
"trail"; m, dark sand and clays; l, light sand and clay;
k, dark sand and clay ; j, yellow sand; i, red sand ; h, light
sand and clay; g, dark sand and clay; f, red sand; e, yellow
sand; d, red sand; o, sand, almost white; b, buff sand, some-
times full of the fossil shells of land and fresh-water molluscs.
These sands represent the sandy margin of the old Thames,
now four miles distant from this spot. Some of the shells found
in it by me have been kindly named by Dr. J. Gwyn Jeffreys;
the series is probably very imperfect, as the time I have for geo-
logical matters is extremely limited; but no doubt the list is
typical, as I have many times met with the species hereafter
mentioned; other species may be more rare or local:—
1. Corbicula fluminalis, Mull.—Extremely common.
2. Hydrobia marginata, Mich.—Not uncommon.
8. Sphaerium corneum, Linn.
4. Pisidium fontinale, Drap.; var. henslowana, Jen.
5. P. amnicum, Mull.
6. Unio tumidus, Phil.
7. Bythinia tentaculata, Linn.—Extremely common, with
abundant free opercula.
8. Valvata piscinalis, Mull.; var. subcylindrica.
9. Planorbis albus, Mull.
10. P. complanatus, Linn.
11. Limnaea auricularia, Linn.
12. L. truncatula, Mull.
13. L. peregra, Mull.
14. Ancylus fluviatilis, Mull.
15. Helix concinna, Jeffr.
16. H. nemoralis, Linn.
Dr. Jeffreys was good enough to add the following note:—
"The occurrence of Pisidium fontinale, var. henslowana, as
well as the tout ensemble of all these fossil shells, induces me