﻿584 
  iiR. 
  g. 
  w. 
  Ljjj:PLr&H 
  ox 
  the 
  

  

  more 
  plentifully, 
  and, 
  as 
  we 
  shall 
  presently 
  see, 
  in 
  at 
  least 
  one 
  other 
  

   case 
  they 
  tend 
  to 
  accumulate 
  in 
  a 
  stony 
  layer. 
  These, 
  though 
  as 
  a 
  

   rule 
  smaller 
  than 
  those 
  in 
  the 
  Coprolite-bed, 
  seem 
  to 
  be 
  the 
  same 
  in 
  

   composition, 
  and 
  have 
  probably 
  had 
  the 
  same 
  origin, 
  whatever 
  that 
  

   may 
  have 
  been. 
  And 
  it 
  seems 
  to 
  me 
  that 
  this 
  coprolitic 
  band 
  may 
  

   have 
  been 
  formed 
  during 
  a 
  period 
  when, 
  either 
  through 
  the 
  increased 
  

   strength 
  of 
  the 
  current, 
  or 
  through 
  lack 
  of 
  material, 
  or 
  from 
  some 
  other 
  

   cause, 
  the 
  deposition 
  of 
  the 
  clay 
  ceased 
  and 
  allowed 
  time 
  for 
  the 
  

   heavier 
  nodular 
  matters 
  dropped 
  over 
  the 
  sea-bottom 
  to 
  accumulate 
  

   as 
  a 
  band. 
  

  

  This 
  Coprolite-bed 
  is 
  undoubtedly 
  a 
  most 
  important 
  horizon 
  in 
  

   the 
  series, 
  both 
  stratigraphically 
  and 
  palEeontologically. 
  There 
  is 
  a 
  

   marked 
  change 
  in 
  the 
  character 
  of 
  the 
  deposits 
  almost 
  immediately 
  

   above 
  it. 
  and 
  also 
  in 
  the 
  fauna. 
  Indeed, 
  of 
  the 
  few 
  Jurassic 
  forms 
  

   which 
  pass 
  it, 
  the 
  doubtful 
  Idngula 
  oralis 
  is 
  the 
  only 
  species 
  yet 
  

   found 
  in 
  the 
  bituminous 
  shales, 
  though 
  our 
  limited 
  knowledge 
  of 
  

   their 
  fauna 
  deprives 
  this 
  observation 
  of 
  much 
  force. 
  

  

  ^Vhen 
  we 
  turn 
  to 
  .Judd's 
  section 
  *, 
  we 
  find 
  that 
  between 
  the 
  

   bituminous 
  shales 
  ( 
  Upper 
  Kimeridge) 
  and 
  this 
  Coprolite-bed 
  he 
  

   intercalates 
  a 
  set 
  of 
  beds 
  of 
  Portlandian 
  age, 
  which 
  are 
  stated 
  to 
  

   consist 
  of, 
  first, 
  a 
  " 
  peaty 
  clay 
  with 
  fish-remains,'' 
  and, 
  below 
  this, 
  

   layers 
  of 
  " 
  dark-coloured 
  clay 
  with 
  hard 
  stony 
  bands." 
  containing 
  

   well-preserved 
  Ammonites 
  of 
  the 
  coronated 
  type. 
  The 
  correlation 
  of 
  

   these 
  strata 
  with 
  the 
  Portlandian 
  rests 
  chiefly 
  on 
  these 
  Ammonites. 
  

  

  Judd 
  does 
  not 
  give 
  the 
  thickness 
  of 
  these 
  beds, 
  and 
  says 
  expressly 
  

   that 
  he 
  did 
  not 
  himself 
  see 
  them, 
  but 
  had 
  had 
  his 
  account 
  of 
  them 
  

   from 
  Leckenby. 
  

  

  These 
  " 
  coronated" 
  Ammonites 
  are 
  to 
  be 
  found 
  in 
  all 
  the 
  old 
  col- 
  

   lections 
  made 
  at 
  Speeton, 
  but 
  it 
  is 
  now 
  very 
  difficult 
  to 
  obtain 
  them, 
  

   so 
  that 
  for 
  a 
  long 
  time 
  I 
  could 
  not 
  make 
  out 
  whence 
  they 
  came. 
  I 
  

   could 
  find 
  no 
  beds 
  among 
  those 
  I 
  had 
  examined 
  below 
  the 
  Coprolite-bed 
  

   in 
  which 
  there 
  was 
  any 
  probability 
  of 
  their 
  occurrence, 
  the 
  mode 
  of 
  

   preservation 
  of 
  these 
  highly 
  inflated 
  forms 
  being 
  totally 
  different 
  from 
  

   the 
  compressed 
  character 
  of 
  all 
  the 
  remains 
  in 
  the 
  bituminous 
  shales, 
  

   wherein, 
  as 
  already 
  stated, 
  the 
  fossils 
  are 
  flattened 
  out 
  even 
  when 
  

   included 
  in 
  the 
  nodules. 
  At 
  length, 
  however, 
  during 
  an 
  exposure 
  

   last 
  autumn, 
  I 
  detected 
  traces 
  of 
  them 
  in 
  the 
  clays 
  of 
  the 
  Lateralis- 
  

   zone 
  at 
  some 
  distance 
  above 
  the 
  Coprolite-bed, 
  and 
  following 
  this 
  

   clue, 
  soon 
  succeeded 
  in 
  finding 
  a 
  good 
  specimen 
  at 
  this 
  horizon. 
  

   This 
  caused 
  me 
  to 
  re-examine 
  the 
  evidence 
  on 
  which 
  was 
  based 
  the 
  

   statement 
  that 
  these 
  fossils 
  came 
  from 
  below 
  the 
  Coprolite-bed, 
  and 
  

   in 
  doing 
  so 
  I 
  compared 
  my 
  own 
  section 
  at 
  Speeton 
  with 
  that 
  of 
  

   Leckenby 
  t 
  and 
  with 
  Judd's. 
  It 
  then 
  became 
  evident 
  that 
  what 
  

  

  * 
  Op. 
  cit. 
  p. 
  23] 
  . 
  

  

  + 
  J. 
  Leckenby. 
  ; 
  Geologist," 
  vol. 
  ii. 
  p. 
  9. 
  This 
  paper 
  extends 
  to 
  barely 
  

   three 
  pages, 
  but 
  contains 
  a 
  detailed 
  section 
  of 
  part 
  of 
  the 
  clays, 
  with 
  lists 
  of 
  

   many 
  of 
  the 
  fossils. 
  These 
  lists 
  are 
  somewhat 
  misleading, 
  since 
  many 
  of 
  the 
  

   commoner 
  fossils 
  are 
  omitted, 
  and 
  often 
  only 
  the 
  rarer 
  forms 
  (recorded 
  under 
  

   little-known 
  names) 
  are 
  mentioned 
  ; 
  indeed 
  it 
  is 
  probable 
  that 
  the 
  section 
  has 
  

   been 
  originally 
  compiled 
  more 
  as 
  a 
  guide 
  to 
  the 
  collection 
  of 
  the 
  rarer 
  fossils 
  

   than 
  as 
  a 
  serious 
  attempt 
  to 
  describe 
  the 
  strata. 
  The 
  sequence, 
  however, 
  is 
  

   accurately 
  given, 
  and 
  the 
  paper 
  is 
  of 
  great 
  value 
  for 
  comparison. 
  

  

  