100 Dr. J. W. Gregory — Fossils from the Loicer Greensand. 



Yenus parva, etc. The three Brachiopoda nearly always occur in the 

 upper part of the English Lower Greensand, when this is fossil- 

 iferous, as in the Bargate Beds near Gnildfoi'd, and in the outliers at 

 Faringdon and LTpware. These five species may be taken as typical 

 of the stage between the Hythe Beds and the Gault. They do not, 

 however, support the division of this interval into two. The faunas 

 of the Folkestone and Sandgate Beds at Folkestone, have been 

 shown by further collecting to be practically identical. Tlie 

 differences between them appear to be only a lithological accident. 

 The collection from Great Chart confirms this view, as the fauna is 

 equally allied to each of the other two. 



Objections to the identification as Sandgate of sundry isolated 

 patches of rocks in the Lower Greensand of Western Kent and 

 Surrey, have frequently been raised. These seem fully justified by 

 the palgeontological evidence which supports the following triple 

 division of the Lower Greensand deposits of the South-east of 

 England : — 



1. Upper Aptian or Gargasian, including Folkestone Beds of Folkestone (excluding 



the mammillare zone). 



Sandgate Beds. 



Phosphatic Beds of Great Chart. 



Bargate Beds of Guildford. 



Fuller's Earth Series of Nutfield. 



Faringdon Sponge Gravels. 



Lower Greensand of TJpware and Bedford- 

 shire. 



2. Lower Aptian or Bedoulian Hythe Beds and Kentish Eag. 



Main Chert Series of Godalming, Hind- 

 head, Ewhurst, and Leith Hill. 



3. llhodanian Atherfield Clay. 



Y. The Synchronism of Parts op the Gault and the Lower 



Greensand. 



Hitherto it has been generally assumed a change from the 

 deposition of sand to that of clay, marked the division between 

 the times of the Lower Greensand and of the Gault. The sands 

 below a certain line are called the "Folkestone Sands" and are 

 included in the Lower Greensand ; the clay immediately above it 

 is regarded as marking the commencement of the Gault. In the 

 Geological Survey maps this lithological change is taken as the line 

 of separation of these two series. For their purposes, this is the 

 only possible and practically useful course that could have been 

 adopted. The palgeontological evidence is too difficult in application. 

 But when this lithological line is accepted as the definite time limit 

 between the periods of the Gault and the Lower Gi'eensand, it is 

 necessary to demur. Another explanation is possible. 



Mr. Meyer showed,^ more than twenty years ago, that the Upper 

 Greensand of Blackdown is really Upper Gault; M. Barrels ^ has 



1 C. J. A. Meyer, "On the Cretaceous Eocks of Beer Head . . . ." Quart. 

 Joiu'n. Geol. Soc. toI. xxx. 1874, p. 385. 



- C. Barrois, " L'age des couches de Blackdown (Devonshire)," Ann. Soc. geol. 

 Nord. t. iii. 1876, pp. 1-8. " Eecherches sur le terrain Cretace superieur de 

 I'Angleterre et de I'lrlande," Mem. Soc. geol. Nord. t. i. 1876, p. 69. 



