﻿ANNIVERSARY 
  ADDRESS 
  OF 
  THE 
  PRESIDENT, 
  lix 
  

  

  But 
  when 
  we 
  come 
  to 
  the 
  Dimyarian 
  Mollusks 
  and 
  the 
  Gaste- 
  

   ropoda, 
  the 
  case 
  is 
  different 
  ; 
  for 
  though, 
  out 
  of 
  27 
  of 
  the 
  former 
  

   and 
  31 
  of 
  the 
  latter 
  (inferred 
  forms) 
  in 
  the 
  Gault, 
  7 
  and 
  8 
  pass 
  

   upwards, 
  yet 
  out 
  of 
  74 
  Dimyaria 
  and 
  62 
  Gasteropoda 
  in 
  the 
  

   Upper 
  Greensand, 
  only 
  1 
  of 
  each 
  goes 
  into 
  the 
  Chalk-marl. 
  With 
  

   the 
  Cephalopoda, 
  however, 
  the 
  proportion 
  of 
  forms 
  of 
  passage 
  is 
  

   much 
  greater, 
  for 
  17 
  inferred 
  (31 
  per 
  cent.) 
  and 
  14 
  known 
  species 
  

   (27 
  per 
  cent.) 
  pass 
  upward 
  from 
  the 
  Gault, 
  and 
  19 
  inferred 
  and 
  14 
  

   known 
  species 
  (46 
  and 
  40 
  per 
  cent.) 
  pass 
  into 
  higher 
  formations 
  from 
  

   the 
  Upper 
  Greensand. 
  I 
  incline 
  with 
  Mr. 
  Godwin- 
  Austen 
  to 
  attribute 
  

   the 
  disappearance 
  of 
  the 
  Dimyaria 
  and 
  Gasteropoda 
  to 
  the 
  deepening 
  

   of 
  the 
  area, 
  accompanied, 
  not 
  by 
  extinction, 
  but 
  by 
  mere 
  migration 
  

   of 
  species. 
  

  

  If 
  we 
  mass 
  the 
  whole, 
  the 
  result 
  is 
  that, 
  out 
  of 
  234 
  inferred, 
  204 
  

   known, 
  and 
  183 
  new 
  forms 
  in 
  the 
  Gault, 
  107, 
  80, 
  and 
  74 
  pass 
  up- 
  

   wards, 
  giving 
  the 
  proportions 
  of 
  about 
  46, 
  40, 
  and 
  40^ 
  per 
  cent., 
  and 
  

   109 
  species 
  are 
  peculiar. 
  

  

  Of 
  412 
  inferred, 
  377 
  known, 
  and 
  305 
  new 
  species 
  in 
  the 
  Upper 
  

   Greensand, 
  109, 
  75, 
  and 
  51 
  pass 
  upward 
  in 
  the 
  proportion 
  of 
  26, 
  

   19|, 
  and 
  about 
  16| 
  per 
  cent. 
  ; 
  while 
  if 
  we 
  eliminate 
  those 
  forms 
  

   specially 
  liable 
  to 
  be 
  affected 
  by 
  change 
  of 
  depth 
  and 
  conditions, 
  

   namely, 
  the 
  Dimyaria 
  and 
  Gasteropoda, 
  the 
  number 
  of 
  species 
  that 
  

   pass 
  upward 
  rises 
  to 
  39 
  per 
  cent. 
  

  

  In 
  the 
  Chalk 
  Marl, 
  of 
  164 
  inferred, 
  93 
  known, 
  and 
  49 
  new 
  

   species, 
  124, 
  55, 
  and 
  33 
  pass 
  up, 
  giving 
  proportions 
  of 
  76, 
  59, 
  

   and 
  67 
  per 
  cent. 
  In 
  the 
  Lower 
  Chalk, 
  of 
  255 
  inferred, 
  223 
  known, 
  

   and 
  130 
  new 
  species, 
  104, 
  69, 
  and 
  39 
  pass 
  into 
  the 
  Upper 
  Chalk, 
  in 
  

   the 
  proportions 
  of 
  about 
  40, 
  31, 
  and 
  30 
  per 
  cent. 
  Here 
  the 
  story 
  ends 
  

   as 
  far 
  as 
  we 
  know 
  it 
  in 
  England 
  ; 
  for 
  of 
  the 
  521 
  species 
  known 
  in 
  our 
  

   Upper 
  Chalk, 
  all, 
  with 
  the 
  exception 
  of 
  Terebratida 
  caput-serpenti$ 
  

   and 
  a 
  few 
  Foraminifera, 
  have 
  apparently 
  become 
  extinct 
  during 
  that 
  

   vast 
  period 
  that 
  elapsed 
  between 
  the 
  close 
  of 
  the 
  Cretaceous 
  and 
  

   the 
  beginning 
  of 
  the 
  Eocene 
  epoch 
  in 
  England 
  — 
  a 
  period 
  of 
  which 
  

   we 
  have 
  no 
  trace 
  in 
  this 
  country, 
  except 
  in 
  the 
  erosion 
  of 
  the 
  Chalk 
  

   and 
  the 
  unconformity 
  of 
  the 
  Eocene 
  beds 
  upon 
  it. 
  

  

  I 
  would 
  fain 
  have 
  continued 
  this 
  discussion, 
  and 
  examined 
  the 
  

   connexion 
  between 
  stratigraphical 
  breaks 
  and 
  breaks 
  in 
  the 
  succes- 
  

   sion 
  of 
  species 
  in 
  the 
  Tertiary 
  epochs; 
  but, 
  though 
  scarcely 
  as 
  a 
  

   connected 
  whole, 
  on 
  this 
  subject 
  much 
  has 
  already 
  been 
  done, 
  and 
  

   for 
  the 
  present 
  I 
  must 
  close 
  with 
  our 
  secondary 
  strata, 
  trusting, 
  if 
  

   worth 
  the 
  pains, 
  to 
  carry 
  on 
  the 
  subject 
  in 
  a 
  special 
  memoir 
  at 
  some 
  

   future 
  time. 
  

  

  The 
  general 
  results 
  obtained 
  from 
  this 
  review 
  of 
  the 
  British 
  secon- 
  

   dary 
  strata 
  may 
  be 
  summed 
  up 
  very 
  briefly. 
  

  

  Between 
  the 
  Bunter 
  and 
  Keuper 
  strata 
  there 
  is 
  a 
  true 
  stratigra- 
  

   phical 
  break, 
  but 
  so 
  difficult 
  to 
  make 
  out, 
  that, 
  until 
  within 
  the 
  last 
  

   few 
  years, 
  the 
  sandy 
  beds 
  at 
  the 
  base 
  of 
  the 
  New 
  Red 
  marl 
  were 
  

   considered 
  part 
  of 
  the 
  Bunter 
  sandstone. 
  Indeed 
  it 
  is 
  only 
  in 
  one 
  

   place 
  observed 
  by 
  Mr. 
  Hull, 
  in 
  a 
  cutting 
  on 
  the 
  St. 
  Helen's 
  railway, 
  

  

  