272 NOTES ON ESSEX GEOLOGY.
Neptunea contraria below (at Beaumont and Walton-on-Naze),
the two being also named as the Oakley Horizon and the
Walton Horizon, a generosity of nomenclature that is hardly to
be recommended.
A list of the. mollusca "most characteristic of the Walton
Crag" is given, with 66 entries, and it is followed by another
list" of northern or recent species . . absent or rare at
Walton," with 28 entries. This seems to be an important
point, and it is one that does not always occur to the compilers
of lists of fossils.
The richness of the Red Crag in fossils is well illustrated by
the work done by Harmer at Beaumont. Many years ago John
Brown, of Stanway, one of the old Essex geologists, got about
100 species of mollusca there, from a pit that was closed years
ago ; but was luckily re-opened in time to absorb some of the
abundant Crag-hunting industry of the author, who succeeded
in finding more than 260 species, including with very few
exceptions, those listed as characteristic of the Walton Crag ;
but also including a few northern shells which are absent or rare
at Walton.
At a new opening which he made at the south-western end
of the Beaumont outlier Harmer got several species that were
not found at the old pit, at the south-eastern end of the outlier,
but which "are all characteristic of the still newer deposit at
Little Oakley."
Five sections in the Little Oakley outlier are marked on
Harmer's map, but apparently from one only, near Poulton Hall,
did he collect, making up, however, for this by fairly exhaustive
work. He says:—"As the Crag of Little Oakley appeared
to be different in age from anything previously known, I de-
termined to work it out as thoroughly as I could," and when
such work has been done by Harmer there can't be much left
for any one else to do.
He succeeded in getting "more than 350 species and well
marked varieties of fossils, some of them new to science, and
many of them known to Wood from the Coralline Crag only.
The presence of so large a number of distinct forms in one
seam, little more than 12 inches thick, and only 10 yards long,
constitutes a striking illustration of the extraordinary richness
of the molluscan fauna of the North Sea at that period." This