22 The Ancient Fauna of Essex. 
in age with the Cyrena- beds of Grays, Erith, and Cray- 
ford. 
“ Such being the case, so much of the Section No. 8, 
given at in 61 of the ‘ Geological Magazine,’ 1866, vol. iii., 
as shows this brick-earth (x 4') underlying the gravel (x 4"), 
is incorrect. 
“The subject, however, is obscure; and while the brick- 
earth at Ilford, Grays, and Erith lies low, and forms a lower 
terrace to the main sheet of the Thames gravel, it rises at 
Crayford to a greater elevation, nearly eighty or ninety feet 
in parts, and forms a high terrace above the gravel of the 
Cray and Darent Valleys, but below the main gravel sheet 
which forms Dartford Heath (see bed h of Section, fig. 9). 
“This anomaly and seeming contradiction is due in my 
view to the reversal of the drainage during the progress of 
the formation of the Thames Valley and the denudation of 
the Weald, as discussed by me in my paper in the Quart. 
Journ. Geol. Soc., 1871, vol. xxviii., p. 3.” 
In order to make the foregoing view more intelligible, 
Mr. S. V. Wood has most obligingly prepared the accom¬ 
panying Section 12 (fig. 9), and adds :— 
“ Crayford is nearer to the region of Wealden elevation 
than the other localities of the Cyrena hrick-eartli; and this 
brick-earth has there been so elevated that the gravel of the 
Cray and Darent Valleys (c of fig. 9) forms in places a very 
distinct deposit occupying the valley-bottoms, and lying at a 
level considerably below that of the Cyrena hrick-eartli. 
This gravel c is, iu my view, a deposit formed since the 
drainage was reversed into its present direction; the Cyrena 
brick-earth, on the other hand, having been deposited while 
the drainage from the Thames Valley flowed into the sea 
which covered the Weald. (See Section). 
“ I should, however, point out, as one of the perplexing 
features of this obscure subject, that if we follow the gravel c 
from the Cray and Darent Valleys to the edge of the Stone 
Marshes, and crossing the Thames pursue it from its re¬ 
appearance above the West Thurrock Marshes to the edge of 
13 Fig. 9 is reproduced from Sir Antonio Brady's ‘ Catalogue of the 
Pleistocene Vertebrata from the Neighbourhood of Ilford, Essex,’ London, 
1874. For other sections prepared by Mr. S. Y. Wood to illustrate the 
Geology of this area, see “ A Day’s Elephant Hunting in Essex,” by Mr. 
Henry Walker, F.G.S., with folding plate of lithographed sections, aud two 
woodcut sections on p. 82, Trans. Essex Field Club, vol. i., pp. 27—58 
(September, 1880). 
