T7PPER AND LOWER CHALK OF DOVER, ETC. 247 



sions receive further confirmation by the study of the chalk of our 

 Kentish cliffs. 



In conclusion, I must thank the Director of the Geological Survey 

 for his kindness in allowing Messrs. Sharman and ]N'ewton to examine 

 and name my fossils, and these gentlemen also for their trouble in 

 working np my somewhat large and rough collection. I must also 

 thank most heartily Mr. Jukes-Browne, F.G.S., for much valuable 

 advice and assistance. 



Discussion. 



Prof. Seeley called attention to the importance of the proofs of 

 erosion in the midst of the Chalk series which had been brought 

 forward by the authors. He had himself pointed out the existence 

 of current-beddiug in a section at Cherry Hinton, and had since ob- 

 served it in many other sections. He agreed with the late Dr. Gwyn 

 Jeffreys that the lower part of the Chalk at least was deposited in 

 moderately shallow water. There were also proofs that the Upper 

 Greensand and Gault, older rocks, were, in some places, denuded 

 during the deposition of the Lower Chalk. He asked for information 

 as to whether the condition described as " brecciated '' was not really 

 " concretionary," like that seen in the Chalk Rock. He had no faith 

 in the classification of the zones of the Chalk by means of its fossils, 

 as hitherto elaborated ; the range of the species was much longer in 

 time than was here supposed, and their use in classification was 

 made to depend on the accidental local abundance of individuals ; 

 and he took exception to those portions of the paper the conclusions 

 of which were based on palseontological evidence of that kind. 



Mr. Whitaker said that good sections had been revealed by the 

 new railway from Winchester to Newbury, showing the presence in 

 that district both of the Melbourn Rock and of the Ciialk Hock. 

 He was prepared to accept the views of the authors as to the erosion 

 of the Chalk strata. He had himself failed to recognize the Chalk 

 Eock at Dover. He could not agree with Prof. Seeley as to the 

 existence of false-bedding at the Cherry-Hinton pit, thinking that 

 the structure taken as false-bedding is a superinduced structure 

 allied to jointing. This structure is found at a particular horizon 

 at many places and in rather clayey chalk. It was very difficult to 

 use the palajontological zones in the mapping of the Chalk. The 

 Chalk Eock is now being worked in the Midland Counties for road- 

 metal, and more pits are now in it than formerly. The Chalk Eock 

 was distinguished palaeontologically by the occurrence of Gasteropoda, 

 so rare generally in the Chalk. 



Mr. ToPLEY asked for information as to the ground for taking the 

 line of the Melbourn 'Rock as the base of the Middle Chalk, instead 

 of the Belemnite-Marls, which are said to be above the line of 

 erosion. While palaeontological zones cannot be mapped, hard rocky 

 bands can be mapped, and are of great use to the geological surveyor. 

 They are sometimes of great importance as water-bearing beds. 



