﻿464 
  PKOE. 
  J. 
  W. 
  JTTDD 
  ON 
  THE 
  EOCENE 
  AND 
  OLIGOCENE 
  

  

  majority 
  of 
  continental 
  palaeontologists, 
  I 
  maintain 
  that 
  Gerithium 
  

   concavum 
  and 
  C. 
  pleurotomoides, 
  are 
  mere 
  varieties 
  of 
  one 
  well-marked 
  

   species, 
  and 
  that 
  both 
  the 
  Headon 
  Sands 
  and 
  Clays 
  belong 
  to 
  the 
  

   zone 
  of 
  Gerithium 
  concavum. 
  

  

  In 
  the 
  discussions 
  which 
  have 
  taken 
  place 
  with 
  respect 
  to 
  these 
  

   Lower 
  Tertiary 
  strata, 
  two 
  perfectly 
  distinct 
  questions 
  are 
  involved 
  — 
  

   first, 
  as 
  to 
  the 
  order 
  of 
  succession 
  of 
  the 
  beds 
  in 
  the 
  Hampshire 
  

   basiu, 
  and, 
  secondly, 
  as 
  to 
  the 
  correlation 
  of 
  those 
  beds 
  with 
  the 
  

   deposits 
  formed 
  during 
  the 
  same 
  great 
  geological 
  periods 
  in 
  other 
  

   areas. 
  

  

  It 
  will 
  manifestly 
  facilitate 
  our 
  fair 
  consideration 
  of 
  these 
  two 
  

   questions, 
  if 
  we 
  treat 
  each 
  of 
  them 
  separately 
  : 
  and 
  such 
  a 
  course 
  is 
  

   fortunately 
  rendered 
  possible 
  by 
  the 
  fact 
  that 
  at 
  WhiteclifF 
  Bay, 
  

   in 
  the 
  Isle 
  of 
  Wight, 
  we 
  have 
  a 
  continuous 
  section 
  of 
  about 
  1900 
  

   feet 
  of 
  nearly 
  vertical 
  strata 
  belonging 
  to 
  the 
  Eocene 
  and 
  Lower 
  

   Oligocene 
  periods 
  ; 
  so 
  that 
  here, 
  at 
  all 
  events, 
  the 
  matter 
  is 
  not 
  com- 
  

   plicated 
  by 
  any 
  doubt 
  as 
  to 
  the 
  true 
  order 
  of 
  succession. 
  The 
  

   vertical 
  position 
  of 
  these 
  beds 
  is 
  not 
  very 
  favourable 
  for 
  the 
  collection 
  

   of 
  fossils 
  from 
  them 
  ; 
  but 
  many 
  of 
  the 
  strata 
  are 
  admirably 
  displayed 
  

   at 
  low 
  water, 
  especially 
  during 
  spring-tides, 
  and 
  yield 
  rich 
  and 
  abun- 
  

   dant 
  faunas. 
  The 
  admirable 
  section 
  of 
  Professor 
  Prestwich* 
  enables 
  

   us 
  to 
  refer 
  without 
  risk 
  of 
  being 
  mistaken 
  to 
  any 
  particular 
  stratum 
  ; 
  

   and 
  the 
  thicknesses 
  of 
  the 
  whole 
  of 
  these 
  beds 
  have 
  been 
  carefully 
  cor- 
  

   rected 
  by 
  Mr. 
  Codrington 
  with 
  the 
  aid 
  of 
  the 
  25-inch 
  maps 
  of 
  the 
  

   Ordnance 
  Survey 
  t. 
  

  

  I 
  am 
  greatly 
  indebted 
  to 
  Mr. 
  Codrington 
  for 
  the 
  loan 
  of 
  the 
  

   manuscript 
  of 
  his 
  detailed 
  section 
  of 
  the 
  beds 
  seen 
  in 
  WhiteclifF 
  Bay, 
  

   which 
  has 
  been 
  of 
  great 
  service 
  to 
  me 
  in 
  my 
  studies. 
  

  

  II. 
  Geological 
  Age 
  of 
  the 
  several 
  Series 
  of 
  Beds 
  exhibited 
  in 
  the 
  

   Whitecliff-Bay 
  Section. 
  

  

  The 
  references 
  made 
  to 
  the 
  several 
  portions 
  of 
  the 
  Whitecliff-Bay 
  

   section 
  in 
  the 
  following 
  pages 
  will 
  be 
  facilitated 
  by 
  the 
  accom- 
  

   panying 
  woodcut 
  (p. 
  465), 
  in 
  which 
  the 
  nature 
  of 
  the 
  several 
  beds 
  is 
  

   indicated 
  by 
  shading. 
  The 
  engraver, 
  in 
  reducing 
  the 
  section 
  to 
  the 
  

   limits 
  of 
  the 
  page, 
  has 
  not 
  very 
  accurately 
  preserved.the 
  relative 
  thick- 
  

   ness 
  of 
  the 
  several 
  beds. 
  These 
  thicknesses, 
  however, 
  are 
  stated 
  

   in 
  the 
  text. 
  The 
  numbers 
  are 
  those 
  of 
  Prof. 
  Prestwich's 
  section. 
  

  

  With 
  respect 
  to 
  the 
  portion 
  of 
  the 
  Whitecliff-Bay 
  section 
  which 
  

   represents 
  the 
  Lower 
  Eocene, 
  there 
  is 
  fortunately 
  little 
  ground 
  for 
  

   difference 
  of 
  opinion. 
  The 
  widely 
  distributed 
  Plastic 
  Clay 
  series 
  of 
  

   the 
  Paris, 
  Hampshire, 
  and 
  London 
  basins 
  is, 
  at 
  WhiteclifF 
  Bay, 
  

   represented 
  by 
  Mr. 
  Prestwich's 
  bed 
  2, 
  here 
  200 
  feet 
  in 
  thick- 
  

   ness, 
  and 
  is 
  seen 
  to 
  be 
  overlain 
  by 
  a 
  series 
  of 
  sands 
  and 
  clays 
  (beds 
  

   3 
  and 
  4 
  of 
  Prestwich) 
  with 
  a 
  tolerably 
  abundant 
  fauna. 
  That 
  this 
  

   series 
  of 
  beds, 
  which 
  is 
  about 
  300 
  feet 
  in 
  thickness, 
  is 
  correctly 
  re- 
  

   ferred 
  to 
  the 
  London 
  Clay 
  has 
  been 
  shown 
  by 
  the 
  valuable 
  researches 
  

  

  * 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  ii. 
  (1846) 
  pi. 
  ix. 
  

   t 
  Ibid. 
  vol. 
  xxiv. 
  (1868) 
  p. 
  519. 
  I 
  

  

  