170 



white, blue, calcareous matter again occur, containing Ammonites 

 rhotomagensis and manteUi, offering a striking contrast to the beds 

 above them and the rock gault immediately below : through this 

 portion again traces of animal life are hardly to be found. 



The gault clay contains Ammonites splendens, A. interruptus, A, 

 auritus, Baculites and Inoceramus gryphaoides, in considerable num- 

 bers, which are continued down into the beds of marly green earth 

 below. c 



This terminates a long-estabHshed division in the cretaceous sefies^ 

 and the abrupt manner in which some of the changes in mineral cha- 

 racter, as from clays to sands or limestone, takes place, is very re- 

 markable. 



Greensand Series. 



Dr. Fitton remarks *, that the tract on the south and west of Guild- 

 ford forms one of the most extensive surfaces of the lower greensand 

 to be found in England ; and he illustrates the succession of the strata 

 in this district by a section from Farnham across Hindhead to the 

 Weald. This line, however, which is taken near the western extre- 

 mity of the major axis of the Wealden denudation, does not exhibit 

 the disturbance to which the preservation of this larger area of lower 

 greensand is due ; and a better line for this purpose is one which 

 may be taken due south from the town of Guildford, and which will 

 cut across the small valley of denudation, which occurs within the 

 said area of the greensand formation, between the chalk range of the 

 North Downs and the escarpment of the Weald valley. 



This denudation has cut through all the beds of the greensand 

 series, as represented, and has laid bare, in the lower parts of the 

 valley, the clays of the Wealden series. 



These clays are noticed by Dr. Fitton f, who states that his atten- 

 tion was first called to them by Mr. Murchison. The discovery of 

 Wealden fossils has enabled the author to confirm Dr. Fitton's con- 

 jecture as to the age of the lowest clays of the Pease marsh, which, 

 even without such aid, is sufficiently established by the general ar- 

 rangement of the greensand series which succeeds it. This structure 

 of the Pease marsh valley had been long known and mapped by Mr. 

 H. L. Long. 



This valley of denudation is rudely elliptical, and like that of the 

 Weald, has its larger axes extended due east and west. The out- 

 ward dip of the beds is most clearly marked, and the general nature 

 of the disturbance can be easily traced by a series of transverse sec- 

 tions, along which the beds of the greensand will be seen to be raised 

 on the north and depressed on the south of the line of disturbance. 



The author considers that an interesting and important member of 

 this group has been overlooked in England, and proposes to adopt (fqr 

 the south-east of England at least) the following subdivisions :— rl' 



a. Upper, ferruginous. 



h. Middle, containing Bargate and Kentish Rag. 



c. Argillaceous [Neocomian of Leymerie and D'Orbigny]. 



* Geo]. Trans., vol. iy. p. 143. f Ibid, p. 149. 



