﻿136 
  PE0CEED1XGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  Plate 
  xxvi. 
  exhibits 
  22 
  vertical 
  comparative 
  sections 
  of 
  the 
  Upper 
  

   Jurassic 
  rocks 
  of 
  the 
  Paris 
  basin 
  and 
  England, 
  — 
  16 
  French, 
  and 
  

   6 
  English. 
  The 
  French 
  series 
  commences 
  with 
  the 
  Ardennes 
  and 
  

   finishes 
  with 
  the 
  Boulonnais, 
  through 
  which 
  every 
  division 
  discussed 
  

   in 
  the 
  paper 
  is 
  shown. 
  Those 
  for 
  England 
  are 
  Dorset, 
  N. 
  Wilts, 
  

   Oxford 
  and 
  Bucks, 
  Cambridge 
  and 
  Lincolnshire, 
  S. 
  Yorkshire 
  and 
  

   ]N*. 
  Yorkshire. 
  The 
  careful 
  perusal 
  of 
  this 
  table 
  will 
  show 
  the 
  nature 
  

   and 
  value 
  of 
  the 
  paper 
  contributed 
  to 
  the 
  Society. 
  

  

  § 
  3. 
  Lias. 
  

  

  The 
  division 
  of 
  the 
  Lias 
  of 
  England 
  into 
  life-zones 
  is 
  of 
  high 
  

   importance 
  ; 
  and 
  of 
  all 
  the 
  zoological 
  groups 
  that 
  afford 
  us 
  reliable 
  

   data 
  for 
  stratigraphical 
  sequence, 
  as 
  indicated 
  by 
  organic 
  remains, 
  

   that 
  of 
  the 
  Cephalopoda 
  stands 
  preeminent. 
  

  

  The 
  tripartite 
  division 
  of 
  the 
  Lias 
  of 
  England 
  is 
  now 
  admitted 
  to 
  

   be 
  the 
  true 
  reading, 
  whether 
  physically 
  or 
  palaeontologically 
  con- 
  

   sidered, 
  and 
  each 
  method 
  confirms 
  the 
  other 
  ; 
  the 
  same 
  law 
  of 
  

   succession 
  and 
  distribution 
  holds 
  good 
  throughout 
  Europe 
  and, 
  where 
  

   known, 
  in 
  America. 
  Taking 
  as 
  examples 
  the 
  magnificent 
  sections 
  

   on 
  the 
  Yorkshire 
  and 
  Dorsetshire 
  coasts, 
  the 
  many 
  localities 
  and 
  

   sections 
  between, 
  and 
  the 
  equivalent 
  succession 
  of 
  strata 
  in 
  France 
  

   and 
  Germany, 
  important 
  generalizations 
  are 
  to 
  be 
  deduced. 
  The 
  

   division 
  of 
  the 
  Lias 
  into 
  three 
  stages 
  is 
  now 
  an 
  acknowledged 
  fact 
  

   throughout 
  Europe 
  ; 
  and 
  these 
  three 
  stages 
  are 
  again 
  subdivided 
  into 
  

   beds 
  or 
  zones 
  which 
  are 
  characterized 
  by 
  certain 
  species 
  of 
  Ammo- 
  

   nites. 
  

  

  The 
  Lower 
  Lias 
  is 
  clearly 
  divisible 
  into 
  seven 
  well-defined 
  hori- 
  

   zons, 
  or 
  zones, 
  characterized 
  b}^ 
  as 
  many 
  species 
  ; 
  reading 
  upwards 
  

   they 
  are 
  as 
  follows 
  : 
  — 
  

  

  7. 
  Arietites 
  (Ammonites) 
  raricostatus, 
  Ziet. 
  

   6. 
  AmcdtJieus 
  (Ammonites) 
  oxynotus, 
  Quenst. 
  

   5. 
  Arietites 
  (Ammonites) 
  obtusus, 
  Sow. 
  

   4. 
  Arietites 
  (Ammonites) 
  Turneri, 
  Sow. 
  

   3. 
  Arietites 
  (Ammonites) 
  BucJdandi, 
  Sow. 
  

   2. 
  JEgoceras 
  (Ammonites) 
  angulatum, 
  Schloth. 
  

   1. 
  JEgoceras 
  (Ammonites) 
  planorbis, 
  Sow. 
  

  

  Below 
  the 
  last-named 
  zone 
  no 
  Ammonite 
  has 
  yet 
  occurred 
  in 
  the 
  

   British 
  Islands. 
  JEgoceras 
  planorbis, 
  either 
  in 
  shales 
  or 
  hard 
  lime- 
  

   stones, 
  rests 
  immediately 
  upon 
  the 
  Rhaetic 
  or 
  Avicula-contorta 
  series, 
  

   with 
  its 
  ever 
  accompanying 
  bed 
  containing 
  remains 
  of 
  reptiles 
  and 
  

   fish, 
  representing 
  the 
  close 
  of 
  the 
  Triassic 
  period 
  or 
  the 
  Passage-beds 
  

   between 
  the 
  Trias 
  (Keuper) 
  and 
  Lower 
  Lias. 
  

  

  Succeeding 
  this, 
  yet 
  physically 
  conformable, 
  although 
  differing 
  

   lithoiogically 
  and 
  largely 
  palaeontologically, 
  comes 
  the 
  middle 
  division 
  

   of 
  the 
  Lias 
  or 
  the 
  "Middle 
  Lias," 
  a 
  series 
  of 
  sandy, 
  marly, 
  and 
  

   usually 
  ferruginous 
  limestones. 
  This 
  group 
  of 
  strata 
  is 
  also 
  essen- 
  

   tially 
  characterized 
  by 
  Cephalopoda 
  (Ammonites), 
  certain 
  forms 
  of 
  

   which 
  hold 
  restricted 
  vertical 
  ranges 
  through 
  this 
  stage. 
  We 
  

  

  