﻿Hv 
  PROCEEDINGS 
  OP 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  (Ostrea 
  acuminata, 
  Rhynchonella 
  varians, 
  TerebratuJa 
  digona, 
  &c.) 
  

   often 
  occur 
  in 
  great 
  numbers. 
  The 
  majority 
  of 
  the 
  forms 
  that 
  passed 
  

   upwards 
  from 
  the 
  Inferior 
  Oolite 
  limestone 
  seem 
  to 
  have 
  fled 
  the 
  

   muddy 
  bottom 
  of 
  the 
  Fuller's 
  Earth 
  sea, 
  and 
  to 
  have 
  returned 
  to 
  the 
  

   same 
  area 
  when 
  the 
  later 
  period 
  of 
  the 
  Great 
  Oolite 
  began. 
  The 
  

   Fuller's 
  Earth, 
  in 
  fact, 
  may 
  be 
  considered 
  only 
  as 
  a 
  comparatively 
  un- 
  

   fossiliferous 
  and 
  inconstant 
  lower 
  zone 
  of 
  the 
  Great 
  Oolite 
  ; 
  for 
  it 
  thins 
  

   out 
  entirely 
  N.E. 
  of 
  Cheltenham, 
  and 
  is 
  overlapped 
  by 
  the 
  Stonesfield 
  

   Slate, 
  which 
  itself 
  is 
  only 
  an 
  inferior 
  member 
  of 
  the 
  Great 
  Oolite. 
  

  

  Great 
  Oolite. 
  — 
  The 
  leading 
  points 
  respecting 
  this 
  formation 
  are 
  as 
  

   follows. 
  

  

  Thirty 
  species 
  of 
  Zoophyta 
  are 
  known, 
  7 
  of 
  which 
  occur 
  in 
  the 
  

   Inferior 
  Oolite, 
  and 
  3 
  pass 
  upwards. 
  Echinodermata, 
  44 
  known 
  and 
  

   4 
  inferred, 
  48 
  in 
  all, 
  18 
  of 
  which 
  (38 
  per 
  cent.) 
  are 
  found 
  lower 
  

   down, 
  and 
  17 
  (35 
  per 
  cent.) 
  pass 
  up. 
  Brachiopoda, 
  18 
  species, 
  4 
  of 
  

   which 
  (22 
  per 
  cent.) 
  occur 
  below, 
  and 
  9 
  (50 
  per 
  cent.) 
  pass 
  upwards. 
  

   Monomyaria, 
  83 
  species, 
  28 
  of 
  which 
  (34 
  per 
  cent.) 
  occur 
  before, 
  

   and 
  24 
  (29 
  per 
  cent.) 
  after; 
  while 
  of 
  the 
  Dimyaria 
  there 
  are 
  

   169 
  species 
  (160 
  known), 
  50 
  of 
  which 
  come 
  up 
  from 
  older 
  times 
  

   (29| 
  per 
  cent.) 
  and 
  33 
  pass 
  upwards 
  (19 
  per 
  cent.). 
  The 
  Gastero- 
  

   poda 
  are 
  remarkable 
  : 
  of 
  255 
  inferred 
  species, 
  250 
  are 
  known, 
  226 
  

   are 
  new, 
  and 
  215 
  are 
  confined 
  to 
  the 
  Great 
  Oolite, 
  while 
  only 
  29 
  

   (11 
  per 
  cent.), 
  have 
  lived 
  on 
  in 
  this 
  area 
  from 
  older 
  horizons, 
  and 
  19 
  

   (about 
  7j 
  per 
  cent.) 
  pass 
  upwards 
  ; 
  the 
  rest 
  have 
  died 
  out 
  or 
  mi- 
  

   grated. 
  It 
  seems 
  likely, 
  however, 
  that 
  the 
  sudden 
  appearance 
  of 
  

   this 
  vast 
  and 
  unusual 
  number 
  of 
  Gasteropoda 
  was 
  due 
  to 
  local 
  con- 
  

   ditions 
  of 
  depth 
  which 
  we 
  cannot 
  trace, 
  and 
  that 
  they 
  both 
  appeared 
  

   and 
  disappeared 
  so 
  suddenly 
  through 
  migration 
  rather 
  than 
  by 
  sudden 
  

   creation 
  and 
  extinction, 
  which, 
  indeed, 
  I 
  do 
  not 
  believe 
  under 
  any 
  

   circumstances 
  ever 
  happened. 
  Of 
  14 
  species 
  of 
  Cephalopoda, 
  only 
  

   one 
  is 
  found 
  in 
  the 
  Inferior 
  Oolite, 
  while 
  another 
  passes 
  upwards 
  to 
  

   the 
  Cornbrash, 
  and 
  13 
  are 
  peculiar 
  to 
  the 
  formation. 
  Fifty 
  species 
  of 
  

   Fish 
  are 
  known, 
  all 
  peculiar 
  except 
  two, 
  which 
  are 
  common 
  to 
  the 
  

   Inferior 
  Oolite. 
  

  

  Here, 
  as 
  in 
  the 
  Inferior 
  Oolite, 
  the 
  Echinodermata 
  are 
  by 
  no 
  means 
  

   very 
  restricted 
  in 
  range 
  ; 
  for 
  whether 
  we 
  take 
  the 
  known 
  or 
  the 
  in- 
  

   ferred 
  species, 
  more 
  than 
  30 
  per 
  cent, 
  pass 
  both 
  up 
  and 
  down; 
  and 
  the 
  

   result 
  is 
  nearly 
  the 
  same 
  with 
  the 
  bivalve 
  Shells. 
  

  

  Taken 
  as 
  a 
  whole, 
  of 
  698 
  known 
  species, 
  125 
  are 
  found 
  in 
  lower 
  

   formations, 
  and 
  89 
  species 
  pass 
  up 
  ) 
  and 
  of 
  718 
  inferred 
  species, 
  141 
  

   (20 
  per 
  cent.) 
  are 
  found 
  in 
  lower 
  and 
  112 
  species 
  (16 
  per 
  cent.) 
  in 
  

   higher 
  formations. 
  If, 
  however, 
  we 
  eliminate 
  the 
  unusual 
  and 
  pro- 
  

   bably 
  accidental 
  presence 
  of 
  so 
  many 
  Gasteropoda, 
  the 
  proportions 
  

   suddenly 
  rise 
  to 
  24 
  per 
  cent, 
  downwards, 
  and 
  20 
  per 
  cent, 
  upwards. 
  

  

  It 
  would 
  be 
  tedious 
  to 
  repeat 
  this 
  style 
  of 
  analysis 
  for 
  each 
  of 
  the 
  

   formations 
  between 
  the 
  Great 
  Oolite 
  and 
  the 
  Portland 
  limestone. 
  

   Enough 
  has 
  been 
  said 
  to 
  show 
  the 
  manner 
  of 
  proceeding, 
  and 
  by 
  

   reference 
  to 
  the 
  tables 
  any 
  one 
  can 
  do 
  the 
  rest 
  for 
  himself. 
  It 
  will 
  

   then 
  be 
  seen 
  that 
  the 
  averages 
  of 
  passage, 
  now 
  up 
  and 
  now 
  down, 
  

   often 
  range 
  among 
  the 
  Echinodermata 
  and 
  bivalve 
  Shells 
  in 
  the 
  

  

  