﻿SUBDIVISIONS 
  OF 
  THE 
  SPEETON 
  CLAY. 
  593 
  

  

  by 
  examinations 
  under 
  favourable 
  circumstances 
  of 
  the 
  cliff-foot 
  

   lying 
  opposite 
  and 
  to 
  the 
  northward 
  *. 
  Since 
  this 
  Belemnite 
  and 
  

   the 
  forms 
  grouped 
  around 
  Bel. 
  semicanaliculatus 
  divide 
  between 
  them 
  

   the 
  Lower 
  Cretaceous 
  part 
  of 
  the 
  section, 
  we, 
  might, 
  if 
  the 
  term 
  Neo- 
  

   comian 
  is 
  to 
  be 
  retained 
  in 
  use, 
  appropriately 
  name 
  this 
  zone 
  the 
  

   Lower 
  Neocomian, 
  and 
  if 
  not, 
  the 
  Lower 
  Speeton 
  Beds 
  ; 
  and 
  the 
  

   overlying 
  beds 
  the 
  Upper 
  Neocomian 
  or 
  the 
  Upper 
  Speeton 
  Beds. 
  

   In 
  doing 
  so, 
  we 
  omit 
  the 
  term 
  Middle 
  Neocomian 
  altogether 
  ; 
  but 
  I 
  

   shall 
  show 
  that 
  this 
  term 
  cannot 
  satisfactorily 
  be 
  applied 
  at 
  Speeton. 
  

  

  I 
  think 
  the 
  description 
  which 
  Judd 
  has 
  given 
  of 
  the 
  range 
  of 
  this 
  

   Belemnite 
  needs 
  some 
  correction, 
  as 
  the 
  fossil 
  is 
  nowhere 
  more 
  

   plentiful 
  than 
  in 
  the 
  iVbWcMS-beds 
  (in 
  which 
  it 
  has 
  been 
  said 
  to 
  be 
  

   very 
  rare), 
  and 
  in 
  its 
  upward 
  range, 
  soon 
  after 
  passing 
  the 
  base 
  of 
  

   the 
  Speetonensis-be&s, 
  though 
  still 
  common 
  enough, 
  it 
  becomes 
  de- 
  

   cidedly 
  less 
  abundant. 
  

  

  Amm, 
  noricus-beds. 
  — 
  The 
  range 
  of 
  Ammonites 
  noricus, 
  which, 
  as 
  

   I 
  have 
  stated, 
  commences 
  with 
  the 
  Compound 
  Nodular 
  Band, 
  thus 
  

   just 
  overlapping 
  into 
  the 
  zone 
  of 
  Bel. 
  lateralis, 
  consists, 
  as 
  my 
  section 
  

   shows, 
  of 
  alternating 
  bands 
  of 
  dark 
  blue 
  and 
  pale 
  blue 
  clays, 
  the 
  

   dark 
  beds 
  on 
  the 
  whole 
  predominating. 
  Nearly 
  all 
  these 
  clays 
  

   contain 
  the 
  small 
  brown-coated 
  " 
  potato-nodules," 
  which 
  are 
  not 
  

   usually 
  fossiliferous. 
  The 
  clays 
  themselves, 
  however, 
  are 
  often 
  rich 
  

   in 
  fossils. 
  

  

  The 
  dark 
  clay 
  (0 
  11) 
  immediately 
  overlying 
  the 
  Compound 
  

   Nodular 
  Band 
  is 
  gritty, 
  and 
  full 
  of 
  dark 
  green 
  and 
  black 
  grains 
  

   (glauconite), 
  which 
  tend, 
  towards 
  the 
  top, 
  to 
  form 
  a 
  distinct 
  seam. 
  

   This 
  bed 
  is 
  very 
  fossiliferous, 
  some 
  of 
  its 
  bedding-planes 
  being 
  

   crowded 
  with 
  specimens 
  of 
  Avicula, 
  Pecten, 
  Ostrea 
  (small 
  species), 
  

   Lima, 
  Leda, 
  and 
  other 
  delicate 
  shells, 
  which 
  will 
  scarcely 
  bear 
  re- 
  

   moval 
  and 
  are 
  therefore 
  for 
  the 
  most 
  part 
  as 
  yet 
  undetermined. 
  

  

  Somewhat 
  higher 
  in 
  the 
  zone 
  {C9), 
  the 
  clays 
  are 
  characterized 
  by 
  

   the 
  abundance 
  of 
  a 
  small 
  shell 
  known 
  in 
  our 
  Yorkshire 
  museums 
  

   under 
  the 
  MS, 
  name 
  of 
  Inoceramus 
  venustulus, 
  Bean, 
  which, 
  so 
  far 
  

   as 
  I 
  know, 
  is 
  peculiar 
  to 
  this 
  portion 
  of 
  the 
  section. 
  

  

  In 
  one 
  of 
  the 
  nodular 
  bands 
  of 
  this 
  zone, 
  that 
  at 
  the 
  base 
  of 
  one 
  

   of 
  the 
  pale 
  seams 
  in 
  09, 
  many 
  of 
  the 
  nodules, 
  instead 
  of 
  being 
  of 
  

   the 
  usual 
  rounded 
  oval 
  shape, 
  assume 
  a 
  flattened 
  outline, 
  and 
  these 
  

   are 
  generally 
  found 
  to 
  enclose 
  specimens 
  of 
  Meyeria 
  ornata, 
  Phil., 
  

   or 
  other 
  crustacean 
  remains. 
  This 
  does 
  not 
  seem, 
  however, 
  to 
  be 
  the 
  

   horizon 
  known 
  to 
  early 
  collectors 
  as 
  the 
  " 
  Shrimp-bed," 
  as 
  Leckenby 
  

   and 
  Judd 
  agree 
  in 
  placing 
  that 
  bed 
  higher 
  in 
  the 
  series 
  ; 
  but 
  the 
  

   fossil 
  has 
  a 
  wide 
  range 
  and 
  may 
  occur 
  anywhere 
  within 
  the 
  zone 
  of 
  

   Bel. 
  jaculnm. 
  

  

  It 
  is 
  not 
  easy 
  to 
  define 
  the 
  exact 
  upward 
  limit 
  of 
  the 
  Noricus- 
  

   beds 
  on 
  the 
  shore, 
  as 
  the 
  fossil 
  becomes 
  somewhat 
  rare 
  in 
  the 
  

   uppermost 
  layers; 
  but 
  I 
  have 
  not 
  found 
  it 
  above 
  the 
  lower 
  of 
  

   two 
  well-marked 
  bands 
  of 
  rather 
  large 
  nodules 
  distinguished 
  by 
  

  

  * 
  A 
  good 
  general 
  knowledge 
  of 
  the 
  sequence 
  of 
  the 
  beds 
  in 
  this 
  zone 
  may 
  be 
  

   gained 
  on 
  the 
  ridge 
  between 
  Black 
  and 
  Middle 
  Cliffs, 
  nearly 
  the 
  whole 
  of 
  its 
  

   thickness 
  being 
  there 
  shown, 
  though 
  in 
  places 
  obscurely. 
  

  

  2x2 
  

  

  