﻿AXXIYERSARY 
  ADDRESS 
  OF 
  THE 
  PRESIDENT, 
  xli 
  

  

  continuity 
  of 
  life 
  and 
  the 
  coincident 
  stratigraphical 
  breaks 
  in 
  this 
  way, 
  

   namely, 
  that 
  they 
  are 
  probably 
  a 
  necessary 
  accompaniment 
  of 
  the 
  

   influences 
  that 
  produced 
  the 
  change 
  of 
  species, 
  especially 
  if 
  we 
  adopt 
  

   the 
  view 
  of 
  descent 
  with 
  modification, 
  in 
  so 
  far 
  that 
  the 
  gaps 
  in 
  the 
  

   geological 
  series 
  of 
  formations 
  indicated 
  by 
  the 
  unconformities, 
  or, 
  in 
  

   other 
  words, 
  the 
  missing 
  records 
  of 
  palaeozoic 
  time 
  are 
  possibly, 
  and 
  

   I 
  believe 
  probably, 
  much 
  longer 
  than 
  those 
  of 
  which 
  the 
  various 
  ex- 
  

   isting 
  Palaeozoic 
  formations 
  of 
  Great 
  Britain 
  bear 
  witness. 
  

  

  I 
  shall 
  now 
  endeavour 
  to 
  discover 
  how 
  far 
  and 
  in 
  what 
  manner 
  

   the 
  same 
  kind 
  of 
  reasoning 
  is 
  applicable 
  to 
  the 
  Secondary 
  strata 
  ; 
  but 
  

   before 
  entering 
  fairly 
  on 
  the 
  subject, 
  I 
  must 
  make 
  a 
  few 
  remarks 
  on 
  

   some 
  points 
  relating 
  to 
  the 
  Palaeozoic 
  formations, 
  which 
  are, 
  in 
  my 
  

   opinion, 
  intimately 
  connected 
  with 
  the 
  newer 
  phase 
  of 
  life 
  of 
  the 
  

   Mesozoic 
  epoch. 
  

  

  Commencement 
  of 
  the 
  Prevalence 
  of 
  Secondary 
  Genera 
  in 
  Carbo- 
  

   niferous 
  times. 
  — 
  First, 
  then, 
  if 
  we 
  examine 
  all 
  the 
  Palaeozoic 
  fossili- 
  

   ferous 
  formations 
  in 
  the 
  British 
  series, 
  it 
  is 
  evident 
  that 
  there 
  is 
  

   towards 
  the 
  end 
  a 
  state 
  of 
  things 
  showing, 
  as 
  it 
  were, 
  an 
  approxima- 
  

   tion 
  to 
  the 
  peculiar 
  grouping 
  that 
  is 
  characteristic 
  of 
  Mesozoic 
  life. 
  

   Thus, 
  if 
  we 
  take 
  the 
  bivalve 
  Shells, 
  the 
  Gasteropoda, 
  and 
  the 
  Cepha- 
  

   lopoda 
  as 
  tests, 
  we 
  roughly 
  find 
  the 
  proportions 
  given 
  in 
  the 
  Table 
  

   on 
  the 
  next 
  page. 
  

  

  From 
  the 
  Table, 
  it 
  is 
  evident 
  that, 
  massing 
  the 
  individual 
  forma- 
  

   tions 
  and 
  ignoring 
  the 
  finer 
  subdivisions, 
  from 
  Lower 
  Silurian 
  to 
  

   Devonian 
  times, 
  the 
  Lamellibranchiate 
  Mollusks, 
  though 
  equal 
  to 
  or 
  

   more 
  numerous 
  generically 
  than 
  the 
  Brachiopoda, 
  are 
  much 
  less 
  nu- 
  

   merous 
  in 
  sj>ecies, 
  and 
  the 
  excess 
  of 
  the 
  latter 
  in 
  Upper 
  Silurian 
  

   times 
  is, 
  perhaps, 
  not 
  greater 
  than 
  we 
  might 
  expect 
  from 
  local 
  

   circumstances. 
  The 
  same 
  kind 
  of 
  remark 
  applies 
  to 
  the 
  Brachiopoda 
  ; 
  

   but 
  while 
  in 
  the 
  Lower 
  Silurian 
  beds 
  the 
  Lamellibranchiata 
  are 
  

   to 
  the 
  Brachiopoda 
  as 
  2 
  to 
  5, 
  in 
  the 
  ITpper 
  Silurian 
  the 
  proportions 
  

   approximate 
  to 
  3 
  of 
  the 
  former 
  to 
  4 
  of 
  the 
  latter 
  ; 
  while 
  in 
  the 
  De- 
  

   vonian 
  rocks 
  the 
  proportions 
  are 
  very 
  nearly 
  the 
  same 
  as 
  in 
  the 
  Lower 
  

   Silurian. 
  It 
  is 
  worthy 
  of 
  remark 
  that 
  the 
  Devonian 
  grouping 
  of 
  

   bivalves 
  thus 
  approaches 
  closely 
  to 
  that 
  of 
  the 
  Silurian 
  rocks, 
  and 
  is 
  

   in 
  this 
  very 
  far 
  removed 
  from 
  the 
  Carboniferous 
  grouping*. 
  TVhen 
  we 
  

   compare 
  the 
  Carboniferous 
  bivalve-fauna 
  with 
  the 
  more 
  ancient 
  palaeo- 
  

   zoic 
  formations, 
  and 
  specially 
  with 
  the 
  Devonian, 
  we 
  find 
  the 
  propor- 
  

   tions 
  of 
  Lamellibranchiate 
  mollusks 
  to 
  the 
  Brachiopoda 
  suddenly 
  re- 
  

   versed, 
  the 
  former 
  being 
  in 
  the 
  proportion 
  of 
  nearly 
  7 
  to 
  3 
  of 
  the 
  latter. 
  

   Indeed 
  it 
  may 
  be 
  said 
  that, 
  while 
  individually, 
  as 
  specimens, 
  the 
  Car- 
  

   boniferous 
  Brachiopoda 
  generally 
  outnumber 
  the 
  Lamellibranchiata, 
  

   the 
  latter, 
  as 
  species, 
  more 
  than 
  double 
  the 
  former. 
  In 
  the 
  scanty 
  

   and 
  imperfect 
  fauna 
  of 
  the 
  Permian 
  beds 
  an 
  analogous 
  development 
  is 
  

   found 
  ; 
  and 
  in 
  both 
  formations 
  the 
  outnumbering 
  of 
  the 
  Brachiopoda 
  

   by 
  the 
  Lamellibranchiata 
  strongly 
  points 
  towards 
  the 
  marvellous 
  

   decline 
  of 
  the 
  one 
  class 
  and 
  the 
  great 
  development 
  of 
  the 
  other 
  in 
  

  

  * 
  More 
  closely 
  analyzed, 
  the 
  Marwood 
  beds 
  form 
  one 
  of 
  the 
  links 
  between 
  

   true 
  Devonian 
  and 
  true 
  Carboniferous, 
  but 
  their 
  fossils 
  are 
  much 
  closer 
  to 
  the 
  

   Carboniferous 
  than 
  to 
  the 
  Devonian 
  type, 
  

  

  