﻿412 stjbdivisioxs of the chalk op teimixgha3i. [aug. i908, 



Discussion. 



Mr. Clejient Eeid spoke of the great value of this palaeontological 

 work, but hoped that Mr. Brydone would reconsider his use of the 

 term ' zone of Terebratulina gracilis.' It was true that the original 

 T. gracilis was a British specimen probably from Trimingham, and 

 that the old ' zone of T. gracilis ' (in the Middle Chalk) did not 

 contain that species. Still, to transfer the name to a totallj'- 

 different part of the Chalk would lead to great confusion. He 

 doubted the occurrence of the strong unconformity depicted in the 

 middle of the Chalk, and showed a photograph of the same mass, 

 taken in 1893 by Dr. Strahan. In this photograph the thin sandy 

 bed (taken by Mr. Brydone as the base of his Grey Chalk) was seen to 

 be folded with the other beds, and not to rest unconformably upon 

 them. The speaker still considered that the disturbance was glacial : 

 the upper beds of the Chalk being contorted without being com- 

 pletely detached. 



The Rev. Edwix Hill highly esteemed such careful records, and 

 regretted that the Author's views could not be presented more 

 satisfactorily that evening. Chalk was exposed elsewhere, both at 

 beach-level and higher : he would wish to have heard what these 

 exposures were. This ' bluff ' he thought a displaced mass : the 

 faults described would result from displacement. 



The ArxHOFv, in reply to Mr. Clement Reid, stated that his chief 

 object in discussing the zonal name of the Trimingham Chalk was 

 to show that the ' zone of Ostrea lunata,' proposed by Mr. Jukes- 

 Browne, was associated with a definition which did not wholly 

 apply to the Trimingham Chalk alone, and part of which only applied 

 to less than half of the minimum thickness. So long as an accurate 

 definition was adopted, it was immaterial which of the fossils 

 restricted to Trimingham was adopted as name-fossil. He also 

 pointed out that a proper deduction to be drawn from the fact 

 that the Grey Chalk was clearly unconformable in the l^orth. Bluff 

 at a point where the junction was in easy reach, but had appeared 

 to Mr. Eeid to be conformable at a point where the junction was 

 higher up and less accessible, was that at the latter point the 

 eroded surface of the White Chalk happened to run parallel to the 

 flint-lines. 



In reply to Mr. Hill, he pointed out that erratics were common 

 in the neighbourhood of Cromer, but were in general highly 

 shattered, and were apparently composed of normal B.-mucronata 

 Chalk, differing thus in toto from the Trimingham Chalk. Also 

 that ' Trimingham Bluffs ' had long been an accepted name for the 

 thi'ee bluffs described by LyeU, two of which were the ' North 

 Bluff' and 'South Bluff' dealt with in the paper, and no other 

 bluffs had ever been heard of by the Author in the area mapped. 



