Vol. 51.] GREENSAND OF EAST SURREY. 123 



at Nuffield, the possible lacustrine sands of Redhill, and the blue 

 stone and associated calcareous beds of Tilburstow Hill Plantation 

 are local formations which can be accounted for variously in the 

 changing conditions of a marine estuary, but, considering their 

 environment, not easily, I think, in any other way. 



In conclusion, I would point out that the Folkestone Sands show 

 deeper-water conditions at Folkestone, where Dr. Hinde has called 

 attention to the sponge-beds, 1 whereas I have lately received from 

 Mr. H. A. Mangles, F.G.S., a fossil fir-cone found by him during 

 excavation in his grounds at Littleworth Cross, Tongham, in West 

 Surrey, on the same horizon. These two observations, takeu together, 

 show clearly in which direction the land lay at that period. 



Discussion. 



Mr. C. J. A. Meier thought the paper a difficult one to discuss, 

 because the Author had discarded the usual subdivisions of the 

 Lower Greensand. He did not see why deep-sea conditions should 

 be supposed to have prevailed during the deposition of the chert- 

 beds of Leith Hill, and shallow-water conditions at the same time 

 only 5 miles to the north. He thought it probable that the 

 development of chert in sand-beds depended partly on the partial 

 exposure of the sand to atmospheric conditions, and that the almost 

 total absence of chert near the escarpment of the North Downs 

 was due in part to the non-exposure of the sand-beds. 



Dr. G. J. Hinde agreed with the Author as to the important 

 development of the beds of sponge-rock in the Lower Greensand of 

 this district. They varied very much in their characters, from a 

 few loose spicules scattered through the sand to beds of solid chert 

 nearly wholly composed of these small bodies. He thought, how- 

 ever, that the Author was in error in considering the chert-beds or 

 sponge-rock in the Greensand as deep-water deposits, for both the 

 nature of the sponge-remains and the associated sandy sediments 

 clearly indicated that they were not formed in deep water. The 

 cherty sponge-rock was of a very resistant character, and fragments 

 of it were widely distributed in areas where the sandy beds had 

 disappeared. 



Dr. 'J. W. Gregory said that he felt much interest in this paper, as 

 he had examined a good deal of the country in the effort to make a 

 map of the coast-line and shore-deposits of the Lower Greensand 

 sea. He worked over the E.eigate-to-Tilburstow area in the 

 winters of 1887-88 and 1888-89, but had left this, as, though the 

 sections were clear, the mapping was more difficult than farther 

 west. He had expressed views generally similar to those of 

 the Author at an excursion of the Geologists' Association (Proc. 

 Geol. Assoc, vol. xiii. pp. 377-381), but differed in some details. 

 Thus he doubted the value of the pebble-beds as a constant horizon : 

 for example, a section at Betchworth, intermediate between two of 

 those described by the Author, showed more than one pebble-bed. 

 He thought that promontories projected from the coast, while on the 

 two sides different deposits were piled up, and these were not capable 

 1 Phil. Trans. Roy. Soc. vol. ckxvi. (18S5) p. 410. 



