﻿lx 
  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  near 
  Ormskirk, 
  that 
  anything 
  like 
  actual 
  unconformity 
  has 
  been 
  

   observed, 
  and 
  even 
  there 
  the 
  appearances 
  are 
  scarcely 
  more 
  marked 
  

   than 
  in 
  many 
  a 
  large 
  case 
  of 
  false 
  bedding, 
  where 
  an 
  upper 
  stratum 
  

   lies 
  on 
  the 
  edges 
  of 
  the 
  oblique 
  lamination 
  below. 
  Yet 
  between 
  

   these 
  formations 
  there 
  is, 
  in 
  England, 
  a 
  gap 
  represented 
  on 
  the 
  Con- 
  

   tinent 
  by 
  two 
  important 
  sets 
  of 
  strata, 
  the 
  Muschelkalk 
  and 
  St. 
  Cas- 
  

   sian 
  beds, 
  containing 
  two 
  great 
  assemblages 
  of 
  fossils 
  perfectly 
  

   distinct 
  from 
  each 
  other. 
  No 
  one 
  could 
  have 
  dreamed 
  of 
  this 
  merely 
  

   from 
  an 
  examination 
  of 
  the 
  English 
  Bunter 
  and 
  Keuper 
  strata. 
  

  

  Such 
  a 
  fact 
  as 
  that 
  stated 
  above 
  ought 
  to 
  act 
  as 
  a 
  thorough 
  cau- 
  

   tion 
  against 
  the 
  frequent 
  assumption 
  that 
  even 
  a 
  formation 
  like 
  the 
  

   Lower 
  Lias 
  is 
  complete 
  ; 
  and 
  if 
  of 
  the 
  Lower 
  Lias, 
  far 
  more 
  so 
  of 
  

   the 
  whole 
  of 
  the 
  Lias 
  series 
  ; 
  and 
  stronger 
  still 
  is 
  the 
  warning 
  that 
  

   may 
  be 
  drawn 
  from 
  such 
  phenomena 
  against 
  the 
  supposed 
  complete- 
  

   ness 
  of 
  the 
  Oolitic 
  formations. 
  Conformities 
  are 
  often 
  accidental, 
  

   and 
  amid 
  the 
  obscurities 
  of 
  the 
  Lower 
  Lias 
  plains 
  of 
  England 
  they 
  

   may 
  well 
  be 
  deceptive 
  : 
  in 
  the 
  Oolitic 
  series 
  we 
  have 
  seen 
  that 
  they 
  

   are 
  so. 
  

  

  Erom 
  the 
  base 
  of 
  the 
  Lias 
  to 
  the 
  Portland 
  stone 
  there 
  is 
  no 
  

   thorough 
  break 
  in 
  the 
  succession 
  of 
  species 
  between 
  any 
  two 
  forma- 
  

   tions. 
  Only 
  in 
  two 
  cases 
  does 
  the 
  break 
  approach 
  completeness, 
  and 
  in 
  

   most 
  of 
  the 
  others 
  a 
  goodly 
  proportion 
  of 
  forms 
  are 
  common 
  both 
  

   to 
  lower 
  and 
  upper 
  formations. 
  I 
  believe, 
  therefore, 
  we 
  are 
  fairly 
  

   justified 
  in 
  the 
  inference 
  that, 
  with 
  regard 
  possibly 
  to 
  the 
  Lias 
  and 
  

   very 
  probably 
  to 
  the 
  Oolites, 
  the 
  partial 
  breaks 
  in 
  succession 
  of 
  

   species 
  resolve 
  themselves 
  into 
  a 
  mixed 
  question 
  of 
  migration 
  and 
  of 
  

   actual 
  gaps 
  among 
  the 
  formations 
  unrepresented 
  by 
  strata, 
  and 
  that 
  

   these 
  gaps, 
  if 
  any, 
  imply 
  spaces 
  of 
  what 
  to 
  us 
  may 
  be 
  called 
  lost 
  or 
  

   unrepresented 
  time, 
  long 
  in 
  themselves, 
  but 
  short 
  compared 
  with 
  that 
  

   which 
  lay 
  between 
  the 
  close 
  of 
  the 
  Portland 
  stone 
  and 
  the 
  begin- 
  

   ning 
  of 
  the 
  Lower 
  Greensand 
  ; 
  for 
  

  

  In 
  the 
  Cretaceous 
  series, 
  alike 
  in 
  the 
  comparatively 
  shallow- 
  water 
  

   beds 
  that 
  commence 
  and 
  in 
  the 
  deep-sea 
  beds 
  that 
  close 
  the 
  depo- 
  

   sits, 
  the 
  break 
  between 
  Oolitic 
  and 
  Cretaceous 
  species 
  is 
  so 
  complete, 
  

   and, 
  what 
  is 
  almost 
  more 
  important, 
  the 
  difference 
  in 
  genera 
  is 
  so 
  

   great, 
  that 
  I 
  cannot 
  but 
  connect 
  these 
  facts 
  with 
  the 
  lapse 
  of 
  a 
  vast 
  

   epoch 
  in 
  time, 
  which 
  with 
  us 
  is 
  represented 
  in 
  part 
  or 
  altogether 
  

   by 
  the 
  Purbeck 
  and 
  Wealden 
  strata. 
  

  

  In 
  other 
  words, 
  making, 
  as 
  we 
  can 
  often 
  do, 
  all 
  liberal 
  allowances 
  

   for 
  diversities 
  of 
  marine 
  and 
  terrestrial 
  conditions, 
  I 
  cannot 
  resist 
  

   the 
  general 
  inference 
  that, 
  in 
  cases 
  of 
  superposition, 
  in 
  proportion 
  as 
  

   the 
  species 
  are 
  more 
  or 
  less 
  continuous, 
  that 
  is 
  to 
  say, 
  as 
  the 
  break 
  in 
  

   life 
  is 
  partial 
  or 
  complete, 
  first 
  in 
  the 
  species, 
  but 
  more 
  importantly 
  in 
  

   the 
  loss 
  of 
  old 
  and 
  the 
  appearance 
  of 
  new 
  allied 
  or 
  unallied 
  genera, 
  so 
  

   ivas 
  the 
  interval 
  of 
  time 
  shorter 
  or 
  longer 
  that 
  elapsed 
  between 
  the 
  close 
  

   of 
  the 
  lower 
  and 
  the 
  commencement 
  of 
  the 
  upper 
  formation', 
  and 
  so 
  it 
  

   often 
  happens 
  that 
  strata 
  a 
  few 
  yards 
  in 
  thickness, 
  or, 
  more 
  notably 
  

   still, 
  the 
  absence 
  of 
  these 
  strata, 
  may 
  serve 
  to 
  indicate 
  a 
  period 
  of 
  time 
  

   as 
  great 
  as 
  the 
  vast 
  accumulations 
  of 
  the 
  whole 
  Silurian 
  series. 
  

  

  