PLEISTOCENE GROLOGV OF THE THAMES VALLEY. 337 



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. 



//. 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 : — 



(i.) 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. 



