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  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  sought 
  for 
  in 
  vain 
  at 
  Swindon. 
  We 
  are 
  led, 
  therefore, 
  to 
  the 
  appa- 
  

   rently 
  strange 
  conclusion 
  that 
  the 
  freshwater 
  strata 
  of 
  Swindon, 
  

   though 
  unconformable 
  to 
  those 
  below, 
  and 
  representing 
  the 
  Purbeck 
  in 
  

   the 
  order 
  of 
  events, 
  are 
  probably 
  in 
  point 
  of 
  actual 
  time 
  as 
  old 
  as 
  some 
  

   parts 
  of 
  the 
  Portland" 
  (loc. 
  cit. 
  p. 
  211). 
  From 
  the 
  4th 
  and 
  5fch 
  

   beds, 
  or 
  sandy 
  beds, 
  Mr. 
  Blake 
  enumerates 
  a 
  large 
  fauna, 
  including 
  

   no 
  less 
  than 
  26 
  genera 
  and 
  41 
  species, 
  35 
  of 
  which 
  are 
  bivalves, 
  

   4 
  univalves, 
  and 
  2 
  Ammonites 
  (A. 
  bipleoc 
  and 
  A. 
  pectinatus). 
  This 
  

   fauna 
  is 
  very 
  distinct 
  from 
  that 
  of 
  the 
  Portland 
  rock. 
  Trigonia 
  

   gibbosa 
  and 
  Cardium 
  dissimile 
  are 
  unknown 
  ; 
  many 
  of 
  the 
  species 
  

   are 
  characteristic 
  of 
  the 
  so-called 
  Middle 
  Portland 
  of 
  Boulogne, 
  or 
  

   of 
  the 
  highest 
  Portlandian 
  beds 
  of 
  other 
  districts. 
  

  

  Buckinghamshire. 
  

  

  The 
  extension 
  of 
  the 
  Portland 
  series 
  through 
  Oxfordshire 
  and 
  

   Buckinghamshire 
  is 
  characterized 
  by 
  much 
  the 
  same 
  conditions 
  

   as 
  that 
  of 
  Swindon, 
  especially 
  through 
  the 
  Limestones, 
  which 
  may 
  be 
  

   an 
  expansion 
  of 
  the 
  Trigonia-be&s 
  ; 
  and 
  it 
  is 
  probable 
  that 
  no 
  higher 
  

   beds 
  were 
  ever 
  deposited 
  in 
  this 
  area 
  above 
  those 
  now 
  exposed. 
  

   Seven 
  beds 
  are 
  recognized 
  in 
  Buckinghamshire. 
  " 
  The 
  creamy 
  

   Limestones 
  of 
  the 
  Brill 
  and 
  Crendon 
  " 
  have 
  yielded 
  a 
  remarkable 
  as- 
  

   semblage 
  of 
  fossils, 
  no 
  less 
  than 
  29 
  genera 
  and 
  45 
  species 
  ; 
  and 
  the 
  

   Bubbly 
  Limestone 
  of 
  bed 
  No. 
  4, 
  19 
  genera 
  and 
  35 
  species. 
  The 
  

   absence 
  of 
  oolitic 
  rocks 
  is 
  remarkable 
  ; 
  the 
  Brill 
  Purbeck 
  beds 
  seem 
  

   to 
  be 
  the 
  only 
  ones 
  possessing 
  that 
  character. 
  

  

  The 
  Bubbly 
  beds 
  at 
  Lodge 
  Hill 
  have 
  yielded 
  a 
  singular 
  assem- 
  

   blage 
  of 
  fossils 
  — 
  few 
  Gasteropoda, 
  but 
  many 
  genera 
  of 
  Bivalves. 
  

   Mr. 
  Blake 
  mentions 
  the 
  important 
  introduction 
  of 
  Ammonites 
  pecti- 
  

   natus 
  of 
  Phillips 
  as 
  argument 
  for 
  correlation. 
  Numerically 
  the 
  

   grouping 
  is 
  as 
  follows 
  : 
  — 
  

  

  Ammonites 
  . 
  . 
  1 
  genus 
  and 
  5 
  species. 
  

  

  Gasteropoda 
  . 
  2 
  genera 
  and 
  2 
  „ 
  

  

  Dimyaria 
  ... 
  9 
  ,, 
  18 
  „ 
  7 
  of 
  these 
  are 
  Trigonice. 
  

  

  Monomyaria 
  . 
  5 
  „ 
  8 
  „ 
  

  

  Annelida 
  ... 
  1 
  „ 
  1 
  „ 
  

  

  Crustacea 
  ... 
  1 
  „ 
  1 
  „ 
  

  

  19 
  35 
  

  

  The 
  Portland 
  rocks 
  of 
  Buckinghamshire 
  probably 
  do 
  not 
  exceed 
  

   60 
  or 
  70 
  feet 
  in 
  thickness, 
  including 
  the 
  sands. 
  This 
  is 
  a 
  con- 
  

   siderable 
  reduction 
  from 
  those 
  of 
  Oxfordshire 
  and 
  Wiltshire. 
  Mr. 
  

   Blake 
  accounts 
  for 
  this 
  in 
  part 
  through 
  the 
  reduction 
  in 
  thickness 
  

   of 
  the 
  Portland 
  Sands 
  ; 
  and 
  he 
  suggests, 
  with 
  regard 
  to 
  the 
  stone, 
  

   that 
  in 
  Buckinghamshire 
  we 
  may 
  have 
  " 
  thin 
  representatives 
  of 
  all 
  

   the 
  Portland 
  deposits, 
  elsewhere 
  reaching 
  a 
  far 
  greater 
  thickness," 
  

   or 
  "that 
  we 
  may 
  match 
  these 
  beds 
  with 
  some 
  part 
  of 
  those 
  at 
  

   Swindon, 
  and 
  that 
  we 
  have 
  in 
  them 
  only 
  a 
  portion 
  of 
  the 
  series 
  

   elsewhere 
  found." 
  

  

  Mr. 
  Blake 
  gives 
  a 
  list 
  of 
  fossils 
  common 
  to 
  the 
  Limestones 
  of 
  

  

  