﻿560 
  ON 
  THE 
  UPPEE 
  JURASSIC 
  CLAYS 
  OF 
  LINCOLNSHIRE. 
  

  

  that 
  the 
  Ampthill 
  Clay, 
  for 
  instance, 
  contained 
  spines 
  of 
  the 
  Corallian 
  

   Urchin 
  Cidaris 
  florigemma. 
  But 
  if 
  from 
  the 
  Corallian 
  rocks 
  we 
  

   eliminate 
  the 
  episodal 
  fauna, 
  we 
  find 
  that 
  a 
  change 
  takes 
  place 
  in 
  

   their 
  midst, 
  the 
  lower 
  portion 
  being 
  Oxfordian, 
  the 
  upper 
  Kimer- 
  

   idgian 
  ; 
  and 
  hence 
  if 
  there 
  be 
  no 
  fossils 
  characteristic 
  of 
  the 
  episode, 
  

   there 
  is 
  little 
  to 
  distinguish 
  the 
  rocks 
  of 
  Corallian 
  age 
  beyond 
  the 
  

   mixture 
  of 
  the 
  two 
  faunas. 
  In 
  Yorkshire 
  Amm. 
  ececavatus 
  is 
  found 
  

   in 
  the 
  Kimeridge 
  Clay. 
  He 
  did 
  not 
  consider 
  the 
  occurrence 
  of 
  

   selenite 
  in 
  the 
  zone 
  as 
  of 
  much 
  value 
  for 
  purposes 
  of 
  correlation 
  ; 
  it 
  

   was 
  a 
  mere 
  question 
  of 
  exposure 
  and 
  oxidation. 
  He 
  referred 
  to 
  

   places 
  in 
  the 
  basal 
  Kimeridge 
  where 
  Ostrea 
  deltoidea 
  is 
  abundant, 
  and 
  

   expressed 
  his 
  agreement 
  with 
  Mr. 
  Roberts 
  . 
  

  

  Mr. 
  Hudleston 
  said 
  that 
  the 
  thanks 
  of 
  geologists 
  were 
  especially 
  

   due 
  to 
  Mr. 
  Roberts 
  for 
  the 
  care 
  he 
  had 
  taken 
  in 
  making 
  out 
  the 
  

   Upper 
  Jurassic 
  Clays 
  of 
  Penland, 
  a 
  task 
  w 
  7 
  hich 
  the 
  nature 
  of 
  the 
  

   country 
  rendered 
  both 
  tiresome 
  and 
  difficult. 
  This 
  paper 
  was 
  a 
  

   supplement 
  to 
  his 
  valuable 
  Sedgwick 
  Prize 
  Essay, 
  and 
  enabled 
  us 
  

   to 
  trace 
  the 
  Corallian 
  Clays 
  of 
  Cambridgeshire 
  still 
  further. 
  But 
  

   in 
  what 
  is 
  now 
  the 
  county 
  of 
  Lincoln 
  the 
  pelolithic 
  conditions 
  of 
  

   the 
  period 
  attained 
  their 
  maximum, 
  and 
  there 
  are 
  neither 
  limestones 
  

   nor 
  grits 
  to 
  help 
  in 
  defining 
  the 
  horizon. 
  Hence 
  the 
  resemblance 
  

   to 
  typical 
  Corallians 
  would 
  naturally 
  be 
  feebler 
  as 
  we 
  proceeded 
  

   northwards 
  from 
  Cambridgeshire. 
  

  

  Notwithstanding 
  the 
  development 
  of 
  typical 
  Corallian 
  rocks 
  round 
  

   the 
  Yale 
  of 
  Pickering, 
  it 
  was 
  found, 
  on 
  making 
  the 
  Hull 
  and 
  Barns- 
  

   ley 
  railway, 
  that 
  the 
  whole 
  of 
  this 
  series 
  of 
  grits 
  and 
  limestones 
  had 
  

   disappeared 
  a 
  few 
  miles 
  south 
  of 
  the 
  Pocklington 
  axis. 
  Hence, 
  

   although 
  the 
  fauna 
  of 
  the 
  Corallian 
  clays 
  of 
  Lincolnshire 
  reminded 
  

   him 
  to 
  a 
  certain 
  extent 
  of 
  the 
  North-Grim 
  ston 
  Cement- 
  stone, 
  the 
  

   affinities 
  of 
  the 
  Lincolnshire 
  beds 
  were 
  rather 
  with 
  those 
  of 
  Cam- 
  

   bridgeshire. 
  Referring 
  to 
  Mr. 
  Roberts's 
  map, 
  he 
  thought 
  that 
  

   possibly 
  the 
  Survey 
  might 
  shrink 
  from 
  the 
  additional 
  task 
  of 
  

   defining 
  the 
  limits 
  of 
  a 
  third 
  clay. 
  

  

  The 
  Author, 
  in 
  reply 
  to 
  Prof. 
  Blake, 
  said 
  that 
  the 
  selenitiferous 
  

   clays 
  contained 
  several 
  characteristic 
  Corallian 
  fossils. 
  The 
  lower 
  

   part 
  of 
  this 
  zone 
  was 
  allied 
  to 
  the 
  Oxford 
  Clay, 
  and 
  its 
  upper 
  part 
  

   to 
  the 
  Kimeridge 
  Clay. 
  He 
  thought 
  there 
  must 
  be 
  some 
  peculiarity 
  

   in 
  the 
  lithological 
  character 
  of 
  those 
  clays 
  which 
  contained 
  so 
  

   much 
  selenite. 
  

  

  