﻿64 
  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [Nov. 
  18, 
  

  

  Starting 
  with 
  this 
  principle, 
  it 
  remains 
  to 
  be 
  seen 
  what 
  is 
  the 
  per- 
  

   centage 
  of 
  existing 
  species 
  in 
  the 
  Javan 
  deposit. 
  

  

  2. 
  Percentage 
  of 
  Recent 
  Species. 
  — 
  From 
  the 
  foregoing 
  descriptions 
  

   and 
  Table 
  it 
  will 
  be 
  seen 
  that 
  Mijnheer 
  de 
  Groot's 
  collection 
  contains 
  

   22 
  species 
  of 
  Mollusca, 
  of 
  which 
  six 
  have 
  not 
  been 
  determined, 
  for 
  

   the 
  reasons 
  already 
  stated 
  ; 
  and 
  that, 
  of 
  the 
  remainder, 
  three 
  are 
  

   still 
  living, 
  and 
  13 
  are 
  new 
  species. 
  

  

  "When 
  it 
  is 
  remembered 
  that 
  only 
  one 
  fossil 
  Shell 
  from 
  Java 
  has 
  

   hitherto 
  been 
  described, 
  and 
  when 
  the 
  distance 
  of 
  the 
  Island 
  from 
  

   any 
  locality 
  where 
  the 
  Tertiary 
  rocks 
  have 
  been 
  well 
  worked 
  out, 
  

   and 
  their 
  fossils 
  properly 
  determined, 
  is 
  taken 
  into 
  consideration, 
  this 
  

   large 
  proportion 
  of 
  new 
  species 
  will 
  not 
  be 
  thought 
  so 
  remarkable 
  

   as 
  might 
  at 
  first 
  sight 
  appear. 
  

  

  As 
  they 
  seem 
  to 
  be 
  unknown 
  forms, 
  it 
  may, 
  perhaps, 
  be 
  assumed 
  

   that 
  all 
  the 
  new 
  species 
  are 
  extinct 
  — 
  although 
  it 
  is 
  probable 
  that 
  

   some 
  of 
  them 
  may 
  eventually 
  be 
  found 
  to 
  exist 
  on 
  the 
  coasts 
  of 
  Java 
  

   or 
  of 
  other 
  islands 
  of 
  the 
  Indian 
  Ocean. 
  If 
  it 
  be 
  granted, 
  then, 
  

   that 
  13 
  out 
  of 
  16 
  species 
  are 
  extinct, 
  the 
  existing 
  species 
  do 
  not 
  con- 
  

   stitute 
  more 
  than 
  19 
  per 
  cent, 
  of 
  the 
  whole; 
  so 
  that, 
  if 
  the 
  percentage 
  

   test 
  can 
  be 
  applied 
  to 
  so 
  small 
  a 
  number 
  of 
  species, 
  these 
  fossils 
  

   must 
  be 
  considered, 
  according 
  to 
  that 
  method, 
  to 
  be 
  approximately 
  

   of 
  the 
  age 
  of 
  the 
  Miocene 
  deposits 
  of 
  Bordeaux 
  and 
  of 
  the 
  Vienna 
  

   Basin. 
  

  

  3. 
  Affinities 
  of 
  the 
  New 
  Species. 
  — 
  The 
  number 
  of 
  species 
  having 
  

   recent 
  alliances 
  is 
  seven 
  ; 
  and 
  the 
  following 
  Table 
  will 
  show 
  that 
  

   these 
  allies 
  all 
  inhabit 
  the 
  Indian 
  Ocean, 
  which 
  is 
  also 
  the 
  habitat 
  

   of 
  the 
  existing 
  species 
  contained 
  in 
  the 
  collection. 
  The 
  extreme 
  

   range 
  of 
  habitat 
  on 
  either 
  side 
  (east 
  and 
  west) 
  occurs 
  in 
  the 
  case 
  of 
  

   known 
  species 
  — 
  namely, 
  Torres 
  Straits, 
  on 
  the 
  east, 
  which 
  is 
  the 
  

   habitat 
  of 
  Pyrula 
  cochlidium, 
  and 
  Africa, 
  on 
  the 
  west, 
  the 
  coasts 
  of 
  

   that 
  continent 
  being 
  the 
  habitat 
  of 
  Oliva 
  utriculus. 
  

  

  Analysis 
  of 
  the 
  Species 
  contained 
  in 
  M. 
  de 
  Groot's 
  Collection. 
  

   A. 
  Recent 
  Species. 
  

  

  Descriptive 
  

   Number. 
  

  

  Species. 
  

  

  Habitat. 
  

  

  5. 
  

  

  7. 
  

  

  11. 
  

  

  

  Torres 
  Straits. 
  

  

  Africa. 
  

  

  Philippines. 
  

  

  

  organic 
  contents 
  of 
  two 
  formations, 
  as 
  shown 
  by 
  the 
  presence 
  of 
  either 
  identical 
  

   or 
  representative 
  species, 
  was 
  a 
  proof 
  of 
  difference 
  in 
  the 
  age 
  of 
  the 
  deposits 
  ; 
  

   more 
  recently, 
  Prof. 
  Huxley 
  has 
  endeavoured 
  to 
  show 
  that 
  faunas 
  and 
  floras 
  

   having 
  distinct 
  facies 
  may 
  be 
  contemporaneous 
  ; 
  but 
  I 
  am 
  not 
  aware 
  that 
  any 
  

   one 
  has 
  yet 
  attempted 
  to 
  prove 
  which 
  of 
  two 
  apparently 
  contemporaneous 
  de- 
  

   posits 
  is 
  the 
  older 
  or 
  the 
  newer. 
  The 
  particular 
  conclusion 
  here 
  arrived 
  at 
  may 
  

   or 
  may 
  not 
  be 
  correct, 
  but 
  I 
  am 
  convinced 
  of 
  the 
  truth 
  of 
  the 
  principles 
  employed, 
  

   and 
  of 
  the 
  importance 
  of 
  the 
  mode 
  of 
  reasoning 
  followed 
  in 
  the 
  above 
  argument. 
  

  

  