FROM THE WHITE CHALK. 



343 



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

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

 cation of the English Chalk. 



" English 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 flints ; (3) Upper Chalk, with flints. But recent researches have shown 

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

 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. 



Cambridgesliire. 

 Jukes-lirowu. 



Norfolk. 

 Woodward. 



a, 



'a 



Upper Chalk 



P 



C Upper zones concealed ■) 



(^ Zone of Micrasters ) 



^Chalk Rock 

 Zone of Holasier planus'] 

 Zone of TerehratuUna \ Medial Chalk and 

 gracilis \- part of the Lower 



"^ Zone of Rhynchonella 

 Cuvieri 

 Melbouru Rock 



L 



o 

 t-1 



Zone of Holaster sitb- 



globosus 

 Totternhoe Stone 



Zone of Rhynchonella 



Martini 

 Cambridge Greensand 



Chalk 



? 



Hunstanton Chalk 

 ? Inpceramus bed 



? Absent 

 Red Chalk in part 



Kent. 

 Price. 



Upper Chalk 



Chalk with flints 



Zone of Terebrahdina 



gracilis 



Zone of Cardiaster yyg- 



mceus 



Belemnite Marl 



Zone of Holaster sub- 



globosus 

 Zone of Ammonites 

 varians 

 Chalk Marl 



Chloritic Marl 



Dorset. 

 Barrois. 



Zone a Belemnitelles. 

 Zone a. Marsupites. 

 Zone a Micraster. 

 Zone a Holaster jilanus. ~) 



Zone a Terebratidina ! 



gracilis. j 



Zone a Inoceramus labia- j 



tus. J 



Marne a Belemnites~) 



plenus. 

 Zone a Holaster sub 



globosus. 



V 



Zone a Pecten asper. 



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

 three minor divisions hitherto called Chloritic Marl, 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 Mantelli, Am. varians, Am. 

 Bhotoma^ensis, Lima glohosa, Tlicatula injlata, Jlhynchonella Martini, Holaster suh- 

 jjldbosus, H. Icevis and Biscoidea subucula. 



^ Eecherches sur le Terrain Cretace Superieur de I'Angleterre et de I'lrlande, Lille, 187G. 



