﻿SUBDIVISIONS 
  OF 
  THE 
  SPEETON 
  CLAY. 
  595 
  

  

  Noricus-beds, 
  at 
  which 
  horizon 
  also 
  Leckenby, 
  it 
  will 
  be 
  noticed, 
  

   has 
  placed 
  his 
  " 
  great 
  band 
  of 
  Hamites" 
  (see 
  fig. 
  2). 
  Judd, 
  how- 
  

   ever, 
  has 
  indicated 
  also 
  in 
  his 
  section 
  a 
  lower 
  band 
  with 
  Ancyloceras, 
  

   agreeing 
  well 
  in 
  position 
  with 
  the 
  bed 
  just 
  named, 
  so 
  that 
  his 
  true 
  

   " 
  dncylocer 
  as 
  -~beds 
  " 
  may 
  occur 
  higher 
  up 
  among 
  the 
  sparingly 
  

   fossiiiferous 
  clays, 
  where 
  as 
  yet 
  I 
  have 
  not 
  been 
  able 
  to 
  recognize 
  

   them. 
  At 
  any 
  rate, 
  above 
  these 
  clays 
  with 
  few 
  fossils 
  we 
  reach 
  a 
  

   series 
  of 
  dark 
  gritty 
  clays 
  with 
  green 
  glauconitic 
  grains, 
  alternating 
  

   with 
  pale 
  nodular 
  bands 
  (0 
  4), 
  in 
  some 
  portions 
  of 
  which 
  fossils 
  

   again 
  become 
  plentiful, 
  and 
  these, 
  it 
  is 
  clear, 
  must 
  be 
  well 
  within 
  

   Judd's 
  " 
  zone 
  of 
  Pecten 
  ductus 
  " 
  (" 
  Middle 
  Neocomian 
  "). 
  We 
  here 
  

   find, 
  along 
  with 
  Bel. 
  jaculum 
  and 
  the 
  small 
  Ammonites 
  nucleus, 
  

   numerous 
  large 
  bivalves 
  of 
  the 
  Oyster 
  family, 
  but 
  the 
  shells 
  are 
  so 
  

   much 
  crushed 
  and 
  disintegrated 
  that 
  it 
  is 
  rarely 
  these 
  can 
  be 
  

   identified. 
  Vermicularia 
  Soiverbyi 
  appears 
  for 
  the 
  first 
  time 
  in 
  the 
  

   upper 
  layers 
  of 
  these 
  clays, 
  and 
  I 
  have 
  obtained 
  shattered 
  examples 
  

   of 
  a 
  very 
  fine 
  Pleurotomaria 
  from 
  the 
  same 
  horizon, 
  along 
  with 
  

   some 
  smaller 
  Gasteropods, 
  Rhynchonellge, 
  and 
  other 
  shells, 
  and 
  

   many 
  Crustacean 
  remains; 
  but 
  it 
  is 
  very 
  difficult 
  to 
  obtain 
  deter- 
  

   minable 
  specimens 
  of 
  the 
  characteristic 
  Pecten, 
  which, 
  except 
  when 
  

   preserved 
  in 
  nodules, 
  is 
  crushed 
  to 
  fragments. 
  I 
  do 
  not 
  see 
  what 
  

   there 
  is 
  in 
  the 
  fauna 
  of 
  these 
  beds 
  that 
  led 
  Judd 
  to 
  adopt 
  the 
  

   term 
  " 
  Middle 
  Neocomian 
  " 
  for 
  them, 
  except 
  Pecten 
  cinctus, 
  which 
  

   was 
  taken 
  as 
  one 
  of 
  the 
  most 
  typical 
  fossils. 
  This 
  shell, 
  however, 
  

   is 
  by 
  no 
  means 
  confined 
  to 
  these 
  beds 
  (as 
  Judd 
  himself 
  admits), 
  nor 
  

   is 
  it 
  in 
  any 
  way 
  peculiar 
  to 
  them, 
  and 
  the 
  only 
  really 
  fine 
  example 
  

   I 
  have 
  obtained 
  of 
  it 
  at 
  Speeton 
  (a 
  perfect 
  specimen 
  eight 
  inches 
  

   across) 
  occurred 
  in 
  tlie 
  Compound 
  Nodular 
  Band. 
  It 
  is 
  stated 
  also 
  

   that 
  in 
  some 
  foreign 
  localities 
  this 
  shell 
  is 
  found 
  in' 
  the 
  Lower 
  

   Neocomian 
  * 
  ; 
  and 
  I 
  have 
  myself 
  found 
  it 
  associated 
  with 
  B. 
  lateralis 
  

   in 
  Lincolnshire. 
  

  

  Moreover, 
  as 
  I 
  shall 
  show 
  that 
  in 
  the 
  bed 
  immediately 
  overlying 
  

   these 
  clays 
  several 
  of 
  the 
  Lower 
  Neocomian 
  Ammonites 
  reappear, 
  

   along 
  with 
  other 
  Lower 
  Neocomian 
  types, 
  it 
  seems 
  scarcely 
  possible 
  

   to 
  establish 
  the 
  " 
  Middle 
  JNeocomian 
  " 
  in 
  this 
  part 
  of 
  the 
  section. 
  

   Nor 
  do 
  I 
  see 
  to 
  what 
  part 
  of 
  the 
  Speeton 
  section 
  the 
  term 
  can 
  with 
  

   any 
  degree 
  of 
  utility 
  be 
  applied, 
  since 
  in 
  descending 
  from 
  the 
  

   " 
  Upper 
  Neocomian 
  " 
  to 
  the 
  top 
  of 
  the 
  zone 
  of 
  Bel. 
  jaculum 
  there 
  

   does 
  not 
  seem 
  to 
  be 
  any 
  palseontological 
  break 
  either 
  at 
  the 
  

   " 
  cement 
  beds" 
  or 
  elsewhere, 
  but, 
  rather, 
  a 
  gradual 
  change 
  of 
  fauna 
  

   throughout, 
  as 
  shown 
  by 
  the 
  overlapping 
  ranges 
  of 
  many 
  of 
  the 
  

   typical 
  species. 
  

  

  The 
  Echinospatangus-6<?<i, 
  03. 
  — 
  Next 
  above 
  the 
  dark 
  gritty 
  clays 
  

   we 
  reach 
  the 
  bed 
  in 
  which, 
  as 
  just 
  stated, 
  the 
  " 
  Lower 
  jSTeocomian" 
  

   forms 
  reappear. 
  This 
  forms 
  a 
  band 
  of 
  pale 
  blue 
  clay, 
  fully 
  eight 
  

   feet 
  thick, 
  with 
  a 
  conspicuous 
  pale 
  yellowish 
  or 
  greenish-grey 
  stony 
  

   layer 
  at 
  its 
  base 
  weathering 
  red 
  in 
  the 
  clifT, 
  which 
  can 
  be 
  best 
  

   examined 
  at 
  the 
  cliff- 
  foot 
  in 
  the 
  great 
  slip 
  in 
  Black 
  Cliff. 
  It 
  may 
  

  

  * 
  Judd, 
  Q. 
  J. 
  G. 
  S. 
  vol. 
  xxvi. 
  p. 
  345, 
  footnote. 
  

  

  