﻿NEWTON: 
  GKOLOGICAL 
  ZONES 
  AND 
  THEIR 
  MOLLUSCA. 
  303 
  

  

  Schloejihachia 
  varians.; 
  Acanthoceras 
  Mantelli, 
  rotomagensis 
  ; 
  Scaphites 
  

   cequalis. 
  Pelecypoda 
  : 
  Inoceramiis 
  latus; 
  Aucellina 
  gryphceoides. 
  

  

  The 
  British 
  Upper 
  Chalk 
  beds 
  were 
  finally 
  classified 
  for 
  the 
  Geological 
  

   Survey 
  by 
  Mr. 
  Jukes-Browne^ 
  in 
  1904, 
  in 
  which 
  the 
  zone 
  of 
  Holaster 
  

   planua 
  was 
  recognized 
  as 
  the 
  base, 
  which 
  differed 
  from 
  liis 
  views 
  of 
  

   1889, 
  when 
  it 
  was 
  regarded 
  as 
  the 
  topmost 
  zone 
  of 
  the 
  Middle 
  Chalk 
  

   (or 
  Turouian), 
  this 
  latter 
  being 
  the 
  position 
  generally 
  acknowledged 
  

   by 
  all 
  authorities 
  on 
  the 
  Chalk 
  zones. 
  

  

  A 
  new 
  zone 
  was 
  established 
  on 
  this 
  occasion 
  for 
  tlie 
  Chalk 
  deposits 
  

   near 
  Trimingham 
  and 
  Mundesley 
  on 
  the 
  Norfolk 
  coast, 
  regarded 
  as 
  the 
  

   highest 
  Chalk 
  of 
  England, 
  which 
  was 
  termed 
  the 
  zone 
  of 
  Odrea 
  

   lunata, 
  its 
  position 
  being 
  just 
  above 
  the 
  Belemnitella 
  mucronata 
  zone. 
  

   The 
  new 
  scheme 
  of 
  zones 
  was 
  as 
  follows 
  : 
  — 
  

  

  Zones. 
  Cuahactekistic 
  Molltjsca. 
  

  

  Ostrea 
  lunata 
  Pelecypoda 
  : 
  Odrea 
  lunata; 
  Pecten 
  

  

  serratus. 
  

   Belemnitella 
  mucronata 
  . 
  . 
  Cephalopoda 
  : 
  Belemnitella 
  mucronata, 
  

  

  lanceolata. 
  

   Actinocamax 
  qiiadratiis 
  . 
  . 
  Cephalopoda 
  : 
  Actinocamax 
  quadratus, 
  

  

  Belemnitella 
  lanceolata. 
  

   Marsupites 
  testudinarius 
  . 
  . 
  Cephalopoda 
  : 
  Ammonites 
  lepto'phyllus 
  ; 
  

  

  Actinocamax 
  verm, 
  granulatus. 
  

   Micraster 
  coranguinum 
  . 
  . 
  Cephalopoda 
  : 
  Actinocamax 
  terns. 
  

  

  Pelecypoda 
  : 
  Inoceramus 
  involutus. 
  

   Micraster 
  cortestudinarium 
  . 
  [No 
  characteristic 
  Mollusca 
  are 
  given.] 
  

   Holaster 
  planus 
  .... 
  Cephalopoda: 
  Heteroceras 
  Reussianiim; 
  

  

  Scaphites 
  Geinit%i 
  ; 
  P 
  achy 
  discus 
  

  

  peramplus. 
  Gastropoda 
  : 
  Trochus 
  

  

  Schliiteri 
  ; 
  SolarieUa 
  gemmata. 
  

  

  Pollowing 
  this, 
  it 
  is 
  important 
  to 
  mention 
  that 
  Mr. 
  li. 
  M. 
  Brydone,- 
  

   wlio 
  had 
  studied 
  the 
  Trimingham 
  Chalk 
  of 
  Norfolk, 
  published, 
  in 
  

   1906, 
  his 
  observations 
  on 
  this 
  subject. 
  He 
  objected 
  to 
  the 
  "zone 
  of 
  

   Ostrea 
  lunata 
  ", 
  established 
  by 
  Mr. 
  Jukes-Browne 
  for 
  the 
  Chalk 
  beds 
  

   of 
  this 
  locality 
  above 
  the 
  Belemnitella 
  mucronata 
  zone, 
  because 
  that 
  

   fossil, 
  although 
  abundantly 
  represented, 
  did 
  not 
  occur 
  throughout 
  the 
  

   whole 
  of 
  the 
  zone; 
  he 
  therefore 
  suggested 
  naming 
  it 
  "the 
  zone 
  of 
  

   Terehratulina 
  gracilis 
  and 
  T. 
  Gisei''\ 
  as 
  those 
  forms 
  of 
  Brachiopods 
  

   were 
  found 
  in 
  ^ 
  all 
  its 
  beds. 
  In 
  a 
  subsequent 
  j)aper 
  on 
  the 
  same 
  subject 
  

   Mr. 
  Brydone 
  again 
  called 
  in 
  question 
  the 
  zone 
  of 
  Ostrea 
  lunata, 
  and 
  

   apparently 
  forgetting 
  that 
  two 
  years 
  previously 
  he 
  had 
  suggested 
  

   anotlier 
  zonal 
  name 
  to 
  take 
  its 
  place, 
  stated 
  that 
  "hence 
  the 
  zone 
  

   of 
  Chalk 
  at 
  Trimingham, 
  lying 
  above 
  the 
  zone 
  oi 
  Belemnitella 
  mucro- 
  

   nata, 
  now 
  divided 
  and 
  defined 
  by 
  me 
  for 
  the 
  first 
  time, 
  requires 
  

   a 
  name 
  ". 
  

  

  ^ 
  Cretaceous 
  Rocks 
  of 
  Britain 
  : 
  The 
  Upper 
  Chalk 
  (Mem. 
  Geol. 
  Surv. 
  United 
  

  

  Kingdom), 
  1904, 
  p. 
  -5. 
  

   " 
  Geological 
  Magazine, 
  1906, 
  p. 
  15. 
  

   " 
  Quart. 
  Journ. 
  Geol. 
  Soc, 
  vol. 
  Ixiv, 
  p. 
  410, 
  1908. 
  

  

  