210
A MANGANIFEROUS CONGLOMERATE IN ESSEX.
water Entomostraca, but there exist in addition a fair number of
smaller papers on different branches of the same subject, a nearly
complete catalogue of which will be found in the Bibliography
appended.
The really earnest student will, however, soon find the need
of something beyond the exclusively English literature, which,
after all, is comparatively meagre. On the Continent a very
large number of works wholly or partially on fresh-water Ento-
mostraca have been published. To merely enumerate a tithe of
these would take much more space than can be allowed here,
but some of the most useful may be referred to. Of the older
works may be mentioned L. Jurine's Histoire des Monocles
(Geneva, 1820), F. Leydig's Naturgeschichte der Daphniden
(Tubingen, 1860), and C. Claus's Die Freilebenden Copepoden
(Leipzig, 1863). The most important of the newer works are
Weismann's Beitrage zur Naturgeschichte der Daphnoiden (107),
Hellich's Die Cladoceren Bohmens (94), Vavra's Monographic der
Ostracoden Bohmens (105), Schmeil's Deutschlands Freilebende Suss-
wasser Copepoden (103), and Richard's Revision des Cladoceres (101).
The two last named contain splendid bibliographies of their
respective subjects.
[To be continued.]
A MANGAN1FEROUS CONGLOMERATE IN
ESSEX.
By T. S. DYMOND, F.I.C, F.C.S.
[Read December 11th, 1897.]
SOME months ago my attention was drawn by Mr. F. W.
Clarke, of Tendring, to the hard flattened masses of
cemented gravel occurring in that locality so near the surface as
to be frequently turned up by the plough, and varying in size
from a few square inches to a square yard. They are referred to
in the Memoir of the Geological Survey (Sheet 48, S.W.) in the
following words :—"East of Colchester the (Glacial Drift) gravel
passes under a sandy loam that covers most of the County as far
as Tendring, beyond which outlying patches of gravel, loam,