PLEISTOCENE GEOLOGY OF THE THAMES VALLEY. 377
divergence of views. Gravels considered by one observer
to be marine are by another termed fluviatile, whilst a
third pronounces them to be glacial. Into the causes of this
divergence of opinion it would be futile to enter, yet we are
disposed to consider that a careful survey of the Pleistocene
Deposits of the Lower Thames Valley will throw light on many
points and may solve some of the problems. It is our intention
to make a detailed examination of these deposits, and thus to lay
the foundation for further speculation in this connection. The
present paper contains the results of our work in the Grays
district, and we venture to think that the nature of these results
justifies us in bringing them before the Essex Field Club.
We would here take the opportunity of thanking the
numerous friends who have so kindly aided us in our researches,
and we would mention Dr. C. W. Andrews, F.G.S., Dr. H. P.
Blackmore, F.G.S., Dr. Frank Corner, F.G.S., Mr. C. V.
Crook, M.A., Mr. J. P. Johnson, Mr. Clement Reid, F.R.S.,
and Mr. B. B. Woodward, F.G.S. Mr. W. Lewis Reid has
accompanied us in the field on many occasions and has
materially helped us in many ways. To Mr. E. T. Newton,
F.R.S., our warmest thanks are due. He has kindly identified
the fish remains, a truly laborious task, and we are also indebted
to him for the sub-section of this paper dealing with the
Pleistocene Ichthyology of Grays.
The Authors desire to place on record their appreciation of
the great service done them by Mr. F. W. Reader, who has
taken a vast amount of trouble in the preparation of the blocks
illustrating this paper, and they here tender him their best
thanks accordingly.
II. BIBLIOGRAPHY.
Note.—Some of the works in the following list do not relate to the Grays
Thurrock area, but since we have had occasion to refer to them in the pre-
paration of this memoir they merit inclusion here : —
(1.) 1836. Morris (Prof. J.)—"On a Freshwater Deposit containing
Mammalian Remains, recently discovered at Grays, Essex." Mag.
Nat. Hist., vol. ix., p. 261.
(2.) 1838. Morris (Prof. J.)—"On the Deposits containing Carnivora and
other Mammalia in the Valley of the Thames." Mag. Nat. Hist.,
ser. 2, vol. ii., p. 539.