﻿1861.] 



WHITAKER CHALK-ROCK OP BERKS, ETC. 



167 



For some time I thought that this bed had escaped the notice of 

 geologists ; but Mr. Prestwich tells me that he has long known of it. 

 It has also been noticed by Mr. Evans, of Hemel Hempstead, and 

 Mr. W. Cunnington, of Devizes. However, I believe that no account 

 of it has yet been published, with the exception of the short de- 

 scription above referred to. 



My own observations have been confined to the counties of "Wilts, 

 Berks, Oxon, Bucks, and Herts — that is, to the northern side of the 

 western part of the London Basin, — in which area I found that the 

 Chalk-rock reaches its greatest thickness to the west, gradually thin- 

 ning eastwards. 



I have found but few fossils in the Chalk-rock ; but Mr. Evans 

 most kindly sent those that he had collected (near Boxmoor) to the 

 Museum of Practical Geology. They have been determined by 

 Mr. Etheridge, and they make up the greater part of the following 

 list;— 



Fossils of the " Chalk-rock." 



Baculites. Spondylus latus. 



Nautilus. Sp. spinosus. 



Ehyncholites (of Nautilus). 



Turrilites. Rbyncbonella Mantelliana. 



Terebratula biplicata. 



Trochus ? T. seiniglobosa. 



Turbo? 



Parasmilia. 



Inoceramus. ■ 



Pachymya ? Ventriculites. 



In Wiltshire I saw only one section of the Chalk-rock, not having 

 time to search for others ; this, however, showed a far greater thickness 

 of it than I have elsewhere seen. It is in a cutting on the turnpike- 

 road leading up the chalk- escarpment that forms the northern side 

 of the Pewsey Valley, nearly four miles S.S.W. of Marlborough. The 

 Chalk-rock is cut into near the top of the hill ; and the following- 

 alternations may be seen in it : — 



ft. in. 



Nodules, with a little cherty flint at the top "1 



in parts > about 3 3 



Hard rocky chalk J 



Nodules 



Hard chalk 



Nodules 



Hard chalk 



Thin line of nodules 



Hard chalk 



Nodules "] 



Hard rocky chalk I g 4 



Marly seam j " 



Hard chalk J 



Nodules » Q 2 



11 4 

 jr 2 



2 3 

 2 4 



