304 EEPORT — T892. 



of France. Between the Isle of Thanet and Folkestone tbe Chalk, accord- 

 ing to Whitaker, Hebert, Price, and others, is divisible into several 

 groups and zones.' Very few of the sections, however, given by Professor 

 Prestwich contain the whole of the beds found in British Senonian rocks. 

 In the nei.Gfhbourhood of Salisbury, according to Mr. B. Westlake,^ we 

 have something like a typical succession ; consequently I shall take this 

 as a preface to other zonal sections which will follow, and indicate the 

 diflFerences by the letters A, B, C, D, E, (F). 



A. Zone of Belemnitella mucronata. Thickness about 100 feet. 

 , B. „ „ quadmla. „ „ 100 ,, 



C. ,, Marsiipites testudinarius, and Holaster pilula. Thickness 

 about 150 feet. 



D. Zone of Micraster cor-anrjuinum. Thickness about 100 feet. 



E. ,, „ cov-testudinarium . „ „ 50 ,, 



(F.) Base (Turonian ?) zone of ifo^as^erjsZaim^. Thickness about 15 

 feet. 



In East Kent the zonal succession of the Upper Chalk is as follows : — 



D. Chalk with flints. Zone Micraster cor-angidnum, Margate. 



E. ,, „ ,, „ cor-tesludinarium, Ramsgate, 

 Broadstairs. 



(F.) Chalk with flints. Zone Holaster planus, St. Margaret. 



In the Isle of Wight, according to Dr. Ch. Barrois, there is a very 

 large development of Chalk of one particular zone (D). 



A. White Chalk. Zone Belemnitella mucronata, 265 feet, 



D. „ „ „ Micraster cor-anguinum, 525 feet. 



E. „ „ ,, ,, cor-testiidinarium, 165 feet. 

 (F.) ,, „ ,, Holaster planus, 65 feet. 



In Surrey, according to Mr. Caleb Evans (Prestwich, ' Geology,' vol. 

 ii., p. 297), the section of the line from Croydon ^through the North 

 Downs shows the following succession in about the thickness of 250 

 feet : — 



D. Zone of Micraster cor-anguinum, Purley beds. 



E. ,, „ cor-testudinarium, Biddlesdown beds. 

 (F.) ,, Holaster planus, Kenley beds. 



In Buckinghamshire and Cambridgeshire (Prestwich, p. 298) only 

 the base of the Upper Chalk is given, and characterised as 



(P.) Zone of Micraster cor-hovis. Chalk with flints. 



The zone of Holaster planus is regarded as the topmost division 

 of the Middle Chalk. 



The subdivisions of the Chalk in Yorkshire, according to Professor 

 Phillips and Mr. Blake (Prestwich, p. 298), are as follows. The thickness 

 of the strata characterised is about 500 feet. 



' ' Outlines of the Geology of Fordingbridge, &c.,' MitchelVs Fordbighridge Alma- 

 TMcTi and Directory, 1889, separate copy, p. 7. 



