PROM THE WHITE CHALK. 



343 



written, viz. in the year 1864. I append now, however, as a condusion to my work, 

 the following remarks by A. J. Jukes-Brown, Esq., E.G.S., on a proposed new classifi- 

 cation of the English Chalk. 



'' EngHsh geologists have hitherto been accustomed to divide the Chalk into three 

 portions, which have long been known by the name of : (1) Chalk Marl ; (2) Lower 

 Chalk, without jflints ; (3) Upper Chalk, with flints. But recent researches have shown 

 that such an arrangement is not supported by either stratigraphical or palseontological 

 evidence, and that the divisions above named do not constitute natural rock-groups. It 

 is time, therefore, that a new nomenclature should be introduced, founded on a better 

 system of classification. 



"D'Orbigny's divisions of Cenomanian, Turonian, and Senonian have long been 

 adopted on the Continent, and in 1875 they were applied to the English Chalk by Dr. 

 Ch. Barrois, who found that even the zonal subdivisions of the system were substantially 

 the same in both countries.^ That system might be accepted in England. 



The zones of the English Chalk in the Eastern and Southern Counties may be thus 

 stated on the authority of the respective authors whose names are appended. 



Cambridgeshire. 

 Jukes-]{rown. 



aj C Upper zones concealed ") 



p (_ Zone of Micrasters ) 



fChalk Rock 



j Zone of Holaster planus~\ 

 ^ Zone of Terebratulina j 

 '^ \ gracilis \- 



Norfolk. 

 Woodward. 



Zone of Rhynchonella 



Cuvieri 

 Melbouru Rock 



fZone of Holaster sub- 

 globosus 

 c Totternlioe Stone 



^ -1 



,3 Zone of Rhynchonella 

 I Martini 



(^Cambridge Greensand 



"Upper Chalk 



? 



Medial Chalk and 



part of the Lower 



Chalk 



? 



Hunstanton Chalk 



? Inoceramus bed 



? Absent 



Red Chalk in part 



Kent. 

 Price. 



Upper Chalk 



Chalk with flints 



Zone of Terebratulina 



gracilis 



Zone of Cardiaster "pyg- 



moBus 



Belemnite Marl 



Zone of Holaster sub- 



globosus 

 Zone of Ammonites 

 varians 

 Chalk Marl 



Chloritic Marl 



Zone a 

 Zone a 

 Zone a 

 Zone a 



Zone 



Zone a 



Marne 



Zone 



Dorset. 

 Barrois. 



Belemnitelles. ") 



Marsupites. > 



Micraster. ) 



Holaster planus. "^ 



I 



a Terebratulina ! 

 gracilis. j 



Inoceramus labia- \ 

 tus. J 



a Belemnites'^ 

 plenus. 

 a Holaster sub 

 globosus. 



Zone a Pecten asper. J 



" It will be seen from the above that the Lower Chalk, may be defined as including the 

 three minor divisions hitherto called Chloritic ]\Iarl, Chalk Marl, and Grey Chalk ; the 

 Totternhoe Stone being only a local development of sandy stone between the two latter. 

 The Lower Chalk will therefore correspond with the Cenomanian of D'Orbigny. It is 

 characterised by an abundance of Cephalopods, Ammonites, Turrilites, Scaphites and 

 Nautili. The most characteristic species are Ammonites ManteUi, Am. varians. Am. 

 Mhotomagensis, Lima glohosa, Plicatula inflata, JRhynchonella Martini, Holaster sub- 

 glohosus, H. Icsvis and Discoidea suhmula, 



1 Eecherches sur le Terrain Cretace Supcrieur de I'Angleterre et de I'lrlande. Lille, 1876. 



