Foraminifera of the Gault of Folkestone. By F. Chapman. 17 
stone partakes of tlie nature of a deeper * * * § water deposit, usually con- 
sisting of dark blue clays in the lower part, whilst the upper part is 
usually a pale grey marl. 
We are indebted, as was previously noticed, to the labours of Messrs. 
De Ranee and Price for the division of the Gault into zones. These 
authors differ in a few details, and in the method of numbering the 
zones. In the present work, the latter author’s arrangement is fol- 
lowed.f 
With regard to the zone xi., in. which the Greensand seam occurs, 
it ajipears advisable to make a further division. Hitherto the upper 
56 ft. 3 in. of pale-grey marl has been referred entirely to zone xi., 
exceeding in thickness that of all the other ten zones together. Con- 
cerning this bed, Mr. A. J. Jukes-Browne has suggested to me the 
following modification. Zone xi. to be measured from the base given 
by Mr. Price, J up to the base of the Greensand seam, and giving a 
thickness of 35 ft. 6 in. The Greensand seam (a glauconitic clay) 
measuring 3 ft. 3 in. just south of Martello Tower No. 3, to be called 
zone xii. From the top of the Greensand seam to the base of the 
Chloritic marl, 17 ft. 6 in., constituting zone xiii. 
This subdivision of the extensive thickness of zone xi. will probably 
facilitate the comparison of their fossil contents, These alterations, 
I learn from Mr. Jukes-Browne, are fully endorsed by Mr. Price 
himself. 
The various seams of Greensand and lines of nodules seen at Folke- 
stone can rarely be traced for any distance from the locality. The 
base of the Gault is usually formed by a bed of Greensand ; and in the 
Isle of Wight, notably at Compton Bay, Sandown Bay, and near Bon- 
church, a bed of Carstone is well seen. This Carstone bed occurs about 
the horizon of the Ammonites ( Acanthoceras ) mammillatus zone of the 
Lower Greensand, together with the basement bed of the Gault, and 
these are referred to as the lowest bed of the Gault (Albian Stage) by 
French geologists. 
The bed of Greensand (zone xii.) at Folkestone has also been 
observed at Eastbourne by Mr. Price. 
As an instance of the great variability in the character of certain 
beds of Gault age, it will only be necessary to refer to the beds of 
“ Red Chalk ” at Hunstanton and Speeton, which are probably on the 
same geological horizon as the upper zones of the Gault ; and in this 
respect it will be instructive to make a comparison between the micro- 
zoic faunas of the two deposits.§ 
With reference to strata of similar age on the Continent, in France 
the series to which d’Orbigny gave the name “ Albien,” commences with 
a sandy layer containing Am. {Acanthoceras) mammillatus ; which zone is 
usually grouped with the Aptian beds of the Lower Greensand by 
English geologists. In the eastern part of the Paris basin this bed is 
* This is used in a comparative sense. 
f It will not be necessary to repeat the diagram and measurements of the zones 
at Copt Point ; for this the papers already mentioned by Messrs. De Kauce and 
Price should be consulted. Details of the chief points of interest in the zonal dis- 
tribution of the Foraminifera are given in the latter part of Appendix IV. 
t The seam of phosphatic nodules containing Pecten Baulimcinus. 
§ See pp. 22, 40-42. 
1898 
c 
