﻿38 
  C. 
  Schicchert— 
  HebeH 
  '«? 
  Views 
  of 
  1857 
  

  

  mud 
  in 
  quiet 
  waters, 
  wherein 
  lived 
  great 
  numbers 
  of 
  quite 
  large 
  

   cephalopods 
  for 
  which 
  waters 
  of 
  a 
  certain 
  depth 
  were 
  necessary. 
  

   That 
  the 
  Coral 
  Rag, 
  from 
  its 
  contact 
  with 
  the 
  Oxford 
  clay, 
  

   was 
  deposited 
  in 
  shallow 
  waters, 
  under 
  physical 
  conditions 
  

   altogether 
  different 
  from 
  those 
  of 
  the 
  preceding 
  epoch, 
  is 
  evi- 
  

   denced 
  by 
  the 
  abundance 
  of 
  zoophytes, 
  often 
  in 
  their 
  original 
  

   places 
  of 
  growth, 
  by 
  the 
  nature 
  of 
  the 
  oolites 
  which 
  make 
  up 
  

   almost 
  all 
  of 
  its 
  mass, 
  by 
  the 
  pebbles 
  or 
  water-worn 
  fossils 
  

   which 
  occur 
  so 
  abundantly, 
  and 
  by 
  the 
  almost 
  complete 
  absence 
  

   in 
  the 
  Paris 
  basin 
  of 
  cephalopods. 
  The 
  Kimmeridge 
  clay, 
  

   including 
  the 
  Astarte 
  limestone 
  and 
  the 
  Portlandian 
  limestone, 
  

   has 
  exactly 
  the 
  same 
  character 
  as 
  the 
  Oxford 
  clay. 
  However, 
  

   it 
  is 
  to 
  the 
  beginning 
  of 
  the 
  Portlandian 
  limestone 
  that 
  the 
  

   maximum 
  depth 
  of 
  seas 
  must 
  correspond 
  ; 
  the 
  end 
  of 
  the 
  

   Jurassic, 
  on 
  the 
  contrary, 
  marked 
  by 
  the 
  Portlandian 
  oolite 
  and 
  

   subordinate 
  beds 
  which 
  do 
  not 
  appear 
  to 
  have 
  been 
  as 
  wide- 
  

   spread 
  as 
  the 
  preceding 
  formations, 
  saw 
  very 
  shallow 
  waters 
  

   covering 
  no 
  more 
  than 
  the 
  center 
  of 
  the 
  basin. 
  Soon 
  the 
  sea 
  

   withdrew 
  completely, 
  and 
  the 
  greatest 
  depression 
  was 
  occupied 
  

   by 
  fresh 
  waters, 
  whose 
  sediments 
  are 
  quite 
  analogous 
  to 
  the 
  

   Purbeck 
  beds. 
  

  

  This 
  progressive 
  upward 
  movement 
  terminated 
  in 
  the 
  emer- 
  

   gence 
  of 
  the 
  basin, 
  which, 
  though 
  not 
  a 
  state 
  of 
  absolute 
  immo- 
  

   bility, 
  lasted 
  during 
  considerable 
  time. 
  

  

  It 
  is 
  to 
  be 
  noted 
  that 
  the 
  same 
  upward 
  movement 
  occurred 
  

   not 
  only 
  in 
  the 
  basin 
  of 
  Aquitaine, 
  but 
  in 
  the 
  Alps 
  and 
  the 
  

   Jura 
  as 
  well. 
  There, 
  as 
  in 
  the 
  Paris 
  basin, 
  the 
  Upper 
  Jurassic 
  

   beds 
  of 
  the 
  Oxfordian 
  stage 
  are 
  superposed, 
  each 
  one 
  " 
  in 
  

   retreat" 
  with 
  respect 
  to 
  the 
  preceding. 
  The 
  sea 
  withdrew 
  

   from 
  this 
  region 
  at 
  the 
  end 
  of 
  the 
  Jurassic, 
  and 
  the 
  final 
  

   depression 
  w 
  T 
  as 
  occupied 
  by 
  fresh 
  waters 
  before 
  the 
  time 
  of 
  the 
  

   Neocomian, 
  according 
  to 
  Lory. 
  This 
  shows 
  that 
  the 
  Paris 
  

   basin 
  took 
  part 
  in 
  a 
  very 
  general 
  movement 
  which 
  affected 
  

   the 
  Aquitaine 
  basin, 
  the 
  Jura 
  and 
  the 
  Alps, 
  i. 
  e., 
  almost 
  all 
  of 
  

   France 
  and 
  probably 
  a 
  great 
  part 
  of 
  Europe. 
  

  

  If 
  we 
  seek 
  to 
  fix 
  exactlv 
  the 
  secondarv 
  movements 
  during 
  

   the 
  emergent 
  period, 
  we 
  shall 
  see 
  that 
  the* 
  depth 
  of 
  water 
  

   must 
  have 
  increased 
  during 
  the 
  whole 
  of 
  the 
  Oxford 
  clay. 
  

   With 
  the 
  beginning 
  of 
  the 
  Coral 
  Pag, 
  and 
  probably 
  also 
  after 
  

   quite 
  a 
  long 
  interruption 
  in 
  sedimentation, 
  the 
  upward 
  move- 
  

   ment 
  again 
  predominated. 
  Then 
  appeared 
  a 
  considerable 
  

   change 
  of 
  fauna 
  without 
  gradual 
  transition. 
  Thus, 
  at 
  the 
  end 
  

   of 
  Oxford 
  time 
  there 
  was 
  not 
  a 
  polyp 
  left 
  in 
  the 
  Paris 
  gulf 
  ; 
  at 
  

   the 
  beginning 
  of 
  the 
  Coral 
  Pag, 
  on 
  the 
  contrary, 
  zoophytes 
  

   were 
  widely 
  spread 
  and 
  the 
  mode 
  of 
  sedimentary 
  formation 
  

   followed 
  altogether 
  different 
  laws. 
  

  

  