Meyer — On the Cretaceous Rocks. 17 



5. The Grault or Folkestone-marl, which, at Folkestone attains a 

 thickness of nearly 130 feet, thins out so considerably to the west 

 of Eeigate as to favour the idea that this bed, like the Sandgate- 

 beds in the Lower Greensand, is, in spite of its great extent, but a 

 subordinate member in the Cretaceous series ; or that, in other 

 words, it may be synchronous in part with the Upper G-reensand, 

 and in part also with the ferruginous beds at the top of the Lower 

 Greensand : as has been suggested by Mr. Seeley with respect to 

 the Carstone-beds of Norfolk. — (Sequence of Eocks and Fossils. 

 Geol. Mag., vol. ii., p. 262.) That such to some extent is the case 

 in the vicinity of Guildford I have little doubt, and probably also in 

 the Isle of Wight, where both the Upper and Lower Greensand 

 strata are so largely developed in comparisen with the Gault. 



Passing further to the westward I should suppose the Gault to be 

 partly represented in the vicinity of Lyme Eegis by the " yellowish- 

 brown sand or Fox Mould" which, forming a bed of from 70 to 80 feet 

 in thickness, ^ interposes itself between the undoubted Upper Green- 

 sand-strata and the Cowstone-beds of the Black Yen section. 



6. The Upper Greensand-strata include, in their passage westward 

 from Folkestone, the Firestone-beds of Godstone and Eeigate, the 

 Malm-rock of Western Sussex, and the Chert-beds of the Isle of 

 Wight ; these latter beds being probably continuous with the 

 " yellowish-brown sandstone with Chert-seams " of Lyme Eegis.. 

 (De la Beche, Trans. Geol. Soc. 2nd ser., vol. ii., p. 113.) 



7. The Chloritic Marl from Folkestone westward to Guildford, is 

 barely recognizable, but becomes a distinct bed in the Isle of Wight. 

 At Pinhay near Lyme Eegis it forms a stratum about four feet in 

 thickness — abounding in fossils, mostly similar to those of Chard- 

 etock and Warminster. 



8. The three succeeding groups — the Chalk-marl, and the Lower 

 and Upper Chalk, are too uniform in their passage from east to west 

 to need special notice, and are therefore merely indicated in the 

 section. 



I have also endeavoured to represent on the section by difference 

 of strength of shading or other markings the lateral passage of 

 argillaceous into arenaceous deposits or of limestone-beds into sand- 

 stone and sand, as in the cases of the Sandgate and Hythe-beds 

 respectively ; the ranges of the particular beds or series of strata 

 named in the margia being shown by the short vertical lines num- 

 bered one to fifteen. The grouping of the faunas, which for want 

 of space I have not mentioned in the text, is also roughly indicated 

 on the section by a series of graduated vertical lines. 



Eegarded as a whole the various groups of strata included in the 

 section are clearly continuous ; that is to say — all were in turn 

 deposited beneath the same ocean without serious break or inter- 

 mission between them. The variations in the mineral character of 

 the beds, and the more or less sudden changes from arenaceous to 

 argillaceous or calcareous deposits being attributable solely to gradual 

 increase or diminution in depth of water, or to change of level, or 

 1 De la Beche, Trans. Geol. Soc, 2nd ser., vol. ii. p. 113. 



VOL. III. — NO. XIX. 2 



