36 Mr. Henry Walker's Lecture:
denne and deer that have been excavated from the same
spot. These identical mollusks, remember, were the con-
temporaries of the mammoth in Britain ! They lived in
the waters which the mammoth frequented, as they have
since shared his grave for thousands of years. We will
consign these precious little relics to the small chip boxes
we carry with us for the purpose, and will label them at
home with name and place of discovery.
This fresh-water mollusk, Cyrena fluminalis, has never
been known in British rivers within the historical period.
It is now to be found in the more tepid waters of the Nile,
whither it must have retreated ages ago, when physical
changes of great importance to the biological world began
to take place in Britain. It is also to be found in certain
streams of central Asia. The visitor to the Uphall pits at
Ilford will have no difficulty in securing specimens of Cyrena
fluminalis for his cabinet. The layer which crops out from
the wall on all sides as we stand in the pit is suggestive of
a large colony of happy mollusks who found here a good
feeding-ground in olden time. A further examination shows
that some of them were drifted here in the post-mortem
stage of their history. The geologist will find shells of
Unio and Anodon as well as of Cyrena at Ilford. And he
may find land shells (also of the mammoth period), as well
as the fresh-water shells we have mentioned. The pretty
helix of the woods (Helix nemoralis), known to Saturday
afternoon ramblers in Epping Forest, is sometimes found
in these elephant beds at Ilford with colour-bands looking
almost as fresh as we may see them in their living
descendants in the hedgerows of to-day.
But suddenly an alarm is given. We are not to invade
these sacred haunts of ancient life with impunity. The
aborigines of the country have been gradually closing in
upon us unseen. They now appear, some of gigantic form,
looking down upon us exultingly from the brink of the pit.
We are fairly caught—outflanked and surrounded by a
wily foe. Not an instant is to be lost. With great presence
of mind Sir Antonio, our leader, advances with dignified
mien to parley with the chief. It is an anxious moment.