﻿302 
  PUOCEEDIITGS 
  OF 
  THE 
  MALACOLOGICAL 
  SOCIETY. 
  

  

  coasidered 
  it 
  to 
  be 
  the 
  topmost 
  bed 
  of 
  the 
  Lower 
  Chalk. 
  Mr. 
  Woods, 
  

   however, 
  regarded 
  it 
  as 
  occurring 
  at 
  the 
  top 
  of 
  the 
  Middle 
  Chalk, 
  that 
  

   is, 
  succeeding 
  the 
  zone 
  of 
  Solader 
  planus 
  and 
  followed 
  by 
  the 
  zone 
  of 
  

   Micraster 
  cortestudinarium. 
  The 
  Chalk 
  E,ock 
  fauna 
  was 
  recognized 
  

   as 
  being 
  distributed 
  over 
  Berkshire, 
  Oxfordshire, 
  Buckinghamshire, 
  

   Wiltshire, 
  Hertfordshire, 
  Kent, 
  Cambridgeshire, 
  and 
  Hampshire, 
  

   being 
  known 
  also 
  on 
  the 
  Continent 
  — 
  France, 
  Germany, 
  etc. 
  As 
  

   in 
  N^orth- 
  Western 
  Germany 
  (Westphalia, 
  etc.), 
  this 
  Chalk 
  bed 
  

   represents 
  the 
  zone 
  of 
  Heteroceras 
  Reussiamim, 
  so 
  Mr. 
  Woods 
  suggested 
  

   the 
  adoption 
  of 
  that 
  name 
  for 
  the 
  zone 
  of 
  the 
  'Chalk 
  Rock' 
  as 
  it 
  

   occurs 
  in 
  this 
  country. 
  The 
  Mollusca 
  described 
  and 
  figured 
  in 
  this 
  

   work 
  comprised 
  Cephalopoda, 
  Gastropoda, 
  Scaphopoda, 
  and 
  Pelecy- 
  

   poda. 
  Instructive 
  tables 
  were 
  given 
  showing 
  the 
  distribution 
  of 
  the 
  

   species 
  throughout 
  the 
  various 
  zones 
  of 
  England, 
  Ireland, 
  and 
  

   European 
  areas. 
  The 
  author 
  considered 
  that 
  the 
  fauna 
  presented 
  

   a 
  Turonian 
  facies, 
  and 
  he 
  also 
  regarded 
  it 
  as 
  of 
  a 
  comparatively 
  

   shallow 
  -water 
  character. 
  

  

  In 
  1889 
  Mr. 
  Jukes-Browne^ 
  formulated 
  a 
  zonal 
  scheme 
  for 
  the 
  

   British 
  Chalk 
  formation, 
  which 
  resembled 
  that 
  of 
  Barrels 
  in 
  its 
  main 
  

   divisions, 
  although 
  fewer 
  Mollusca 
  were 
  used 
  for 
  the 
  index-fossils 
  — 
  

  

  iZone 
  of 
  3[arsupites. 
  

   ,, 
  Micraster 
  coranguinum. 
  

   ,, 
  jlf, 
  cortestudinariuni. 
  

   Chalk 
  Bock. 
  

   / 
  Zone 
  of 
  Ilolaster 
  planus. 
  

   ^^r 
  ^ 
  ] 
  ,, 
  Terehratidina 
  qracilis. 
  

  

  JNilDDLE 
  UHALK 
  > 
  y-,, 
  7 
  77 
  V< 
  • 
  • 
  

  

  j 
  ,, 
  RhynclioneUa 
  Cuvieri. 
  

  

  \ 
  Melbourn 
  Bock 
  at 
  base. 
  

  

  / 
  Zone 
  of 
  Belemnitella 
  plena. 
  

  

  T 
  n 
  ' 
  55 
  Bolaster 
  suhqlohosxis. 
  with 
  Totternhoe 
  Stone 
  

  

  Lower 
  Chalk 
  / 
  " 
  , 
  , 
  J 
  ' 
  

  

  i 
  at 
  base. 
  

  

  ' 
  ,, 
  Ammonites 
  varians. 
  

  

  Another 
  scheme 
  was 
  pi'oposed 
  by 
  Mr. 
  Jukes-Browne- 
  in 
  1903 
  for 
  

   subdividing 
  the 
  Lower 
  and 
  Middle 
  Chalk 
  of 
  England 
  into 
  zones, 
  which 
  

   differed 
  from 
  that 
  of 
  1889, 
  as 
  each 
  division 
  was 
  formed 
  of 
  two 
  zones 
  

   instead 
  of 
  three. 
  These, 
  with 
  their 
  characteristic 
  Mollusca, 
  were 
  as 
  

   follows 
  : 
  — 
  

  

  Middle 
  Chalk 
  (zone 
  of 
  Ih'ehrat^dina 
  gracilis, 
  yhx. 
  lata). 
  Cephalo- 
  

   poda: 
  Prionotropis 
  Woolgari; 
  Pachydiscus 
  peramplus; 
  Ilaploceras 
  

   peramplus. 
  Pelecypoda: 
  Inoceramus 
  Cuvieri; 
  Spo7idylus 
  spinosus. 
  

   (Zone 
  of 
  Rhynchonella 
  Cuvieri.) 
  Cephalopoda 
  : 
  Acanthoeeras 
  

   nodosoides. 
  Pelecypoda 
  : 
  Inoceramiis 
  mytiloides. 
  

   Loaver 
  Chalk 
  (zone 
  of 
  Jlolaster 
  stcbglobosus). 
  Cephalopoda 
  : 
  

   Acanthoeeras 
  navicularis, 
  rotomagensis 
  ; 
  Haploeeras 
  Austeni 
  ; 
  

   Actinocamax 
  plenus. 
  (Zone 
  of 
  Ammonites 
  varians.) 
  Cephalopoda: 
  

  

  ^ 
  In 
  W. 
  Whitaker's 
  The 
  Geology 
  of 
  London 
  (Mem. 
  Geol. 
  Surv. 
  England 
  and 
  

  

  Wales), 
  vol. 
  i, 
  p. 
  58, 
  1889. 
  

   ^ 
  Cretaceous 
  Bods 
  of 
  Britain 
  : 
  The 
  Lotver 
  and 
  Middle 
  Chalk 
  of 
  England 
  

  

  (Mem. 
  Geol. 
  Sm^v. 
  United 
  KmgxTom), 
  1903, 
  p. 
  558. 
  

  

  