﻿70 
  . 
  PKOCEEDLNGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  size'of 
  the 
  British 
  Isles, 
  the 
  breaks 
  in 
  stratigraphy, 
  whether 
  peno- 
  

   logical 
  or 
  palaeontological, 
  must 
  first 
  receive 
  attention, 
  and 
  that 
  such 
  

   breaks 
  must 
  be 
  accepted 
  as 
  limits 
  of 
  the 
  subdivisions 
  in 
  which 
  the 
  

   strata 
  are 
  arranged, 
  — 
  if, 
  in 
  short, 
  it 
  were 
  urged 
  that 
  a 
  local 
  classifi- 
  

   cation 
  must 
  depend 
  upon 
  different 
  considerations 
  from 
  those 
  deemed 
  

   of 
  primary 
  importance 
  in 
  a 
  general 
  classification, 
  his 
  views 
  would 
  

   necessarily 
  deserve 
  acceptance, 
  since 
  he 
  would 
  only 
  recapitulate 
  

   the 
  facts 
  upon 
  which 
  all 
  local 
  classifications 
  have 
  been 
  based. 
  But, 
  

   if 
  I 
  understand 
  him 
  rightly, 
  this 
  is 
  not 
  the 
  position 
  he 
  takes. 
  He 
  

   contends 
  that 
  palaeontological 
  classification, 
  and 
  especially 
  a 
  classi- 
  

   fication 
  by 
  marine 
  or 
  " 
  pelagic 
  " 
  types 
  of 
  life, 
  is 
  artificial, 
  and 
  that 
  

   the 
  only 
  natural 
  classification 
  is 
  founded 
  upon 
  local 
  breaks 
  in 
  sedi- 
  

   mentation 
  or 
  in 
  life. 
  I 
  am 
  unable 
  to 
  agree 
  with 
  any 
  of 
  the 
  above 
  

   contentions, 
  and 
  I 
  must 
  say 
  that 
  I 
  shall 
  be 
  very 
  much 
  surprised 
  if 
  

   in 
  these 
  points 
  Prof. 
  Hughes 
  represents 
  the 
  views 
  of 
  British 
  geolo- 
  

   gists 
  in 
  general. 
  Indeed, 
  in 
  some 
  of 
  the 
  Heports 
  that 
  follow 
  his 
  

   preface, 
  for 
  instance 
  in 
  the 
  remarks 
  by 
  Messrs. 
  Jukes-Browne 
  and 
  

   Topley 
  on 
  the 
  Purbeck 
  beds 
  (p. 
  73), 
  I 
  find 
  precisely 
  the 
  opinions 
  

   put 
  forward 
  with 
  regard 
  to 
  the 
  part 
  played 
  by 
  marine 
  faunas 
  in 
  

   classification 
  that 
  I 
  have 
  hitherto 
  understood 
  to 
  be 
  generally 
  held 
  

   amongst 
  geologists 
  throughout 
  the 
  world. 
  

  

  There 
  can 
  be 
  no 
  question 
  that 
  all 
  breaks 
  in 
  stratigraphy 
  are 
  

   local, 
  and 
  that 
  such 
  breaks 
  are 
  or 
  may 
  be 
  represented 
  elsewhere 
  

   by 
  beds. 
  Moreover 
  local 
  breaks 
  are 
  very 
  often 
  misleading, 
  because 
  

   the 
  amount 
  of 
  change, 
  and 
  especially 
  of 
  unconformity, 
  is 
  not 
  pro- 
  

   portionate 
  to 
  the 
  lapse 
  of 
  time, 
  but 
  depends 
  on 
  phenomena 
  often 
  

   confined 
  to 
  a 
  limited 
  area, 
  and 
  which 
  may 
  have 
  been 
  of 
  no 
  great 
  

   duration 
  or 
  real 
  importance. 
  Thus 
  the 
  great 
  break 
  and 
  uncon- 
  

   formity 
  between 
  the 
  Coal-measures 
  and 
  Permian 
  in 
  Great 
  Britain 
  

   is 
  shown 
  to 
  be 
  representative 
  of 
  but 
  little 
  lapse 
  of 
  time 
  by 
  the 
  fact 
  

   that 
  no 
  change 
  of 
  any 
  importance 
  took 
  place 
  in 
  the 
  marine 
  fauna, 
  

   the 
  alteration 
  in 
  which 
  between 
  the 
  Carboniferous 
  Limestone 
  that 
  

   preceded 
  the 
  Coal-measures, 
  and 
  the 
  Permian 
  magnesian 
  limestone, 
  

   is 
  actually 
  less 
  than 
  that 
  between 
  Devonian 
  and 
  Carboniferous, 
  

   which 
  are 
  not 
  separated 
  by 
  any 
  important 
  stratigraphical 
  break. 
  

   If 
  any 
  great 
  lapse 
  of 
  time, 
  or 
  any 
  widespread 
  physical 
  changes, 
  

   corresponded 
  to 
  the 
  local 
  break 
  between 
  Carboniferous 
  and 
  Per- 
  

   mian 
  in 
  England, 
  it 
  may 
  reasonably 
  be 
  assumed 
  that 
  a 
  great 
  

   change 
  in 
  marine 
  life 
  would 
  have 
  taken 
  place 
  in 
  the 
  interval. 
  

  

  The 
  argument 
  to 
  which 
  Professor 
  Hughes 
  naturally 
  refers, 
  that 
  

   identity 
  of 
  marine 
  fossils 
  in 
  distant 
  localities 
  does 
  not 
  prove 
  

  

  