﻿SUBDIVISIONS 
  OF 
  THE 
  SPEETON 
  CLAY. 
  611 
  

  

  separated 
  as 
  they 
  are 
  by 
  more 
  than 
  120 
  feet 
  of 
  clay 
  in 
  which 
  neither 
  

   occurs, 
  are 
  undoubtedly 
  specifically 
  distinct. 
  

  

  I 
  have 
  not 
  found 
  any 
  Belemnite 
  within 
  the 
  range 
  of 
  Bel. 
  lateralis 
  

   which 
  could 
  not 
  be 
  referred 
  to 
  that 
  species 
  ; 
  nor 
  have 
  I 
  found 
  any 
  

   undoubted 
  specimen 
  of 
  the 
  species 
  above 
  the 
  Compound 
  Nodular 
  

   Band. 
  

  

  Belemnites 
  jacultjm, 
  Phil. 
  

  

  This 
  very 
  well-marked 
  " 
  hastate 
  " 
  form, 
  which 
  occurs 
  in 
  great 
  

   profusion 
  at 
  Speeton, 
  though 
  it 
  varies 
  in 
  shape 
  between 
  the 
  slender 
  

   graceful 
  outline 
  of 
  Bel. 
  subfusiformis, 
  Raspail, 
  and 
  the 
  extremely 
  

   obtuse 
  form 
  of 
  Bel. 
  pistilliformis, 
  Blainville, 
  maintains 
  throughout 
  

   its 
  zone 
  its 
  easily 
  recognizable 
  specific 
  characters. 
  

  

  The 
  variety 
  p\ 
  Istilliformis 
  is 
  most 
  abundant 
  towards 
  the 
  base 
  of 
  the 
  

   Speetonensis-beds, 
  and 
  does 
  not 
  seem 
  to 
  range 
  much 
  higher. 
  The 
  

   slender 
  form, 
  on 
  the 
  other 
  hand, 
  ranges 
  throughout 
  the 
  zone. 
  Spe- 
  

   cimens 
  in 
  which 
  the 
  phragmocone 
  is 
  preserved 
  are 
  rare. 
  

  

  This 
  species 
  does 
  not 
  die 
  out 
  in 
  the 
  abrupt 
  manner 
  of 
  Bel. 
  lateralis, 
  

   but 
  lingers 
  on 
  in 
  a 
  few 
  dwarfed 
  specimens 
  into 
  beds 
  some 
  distance 
  

   above 
  the 
  limits 
  assigned 
  to 
  it 
  in 
  my 
  section. 
  There 
  is 
  also 
  (as 
  

   mentioned 
  at 
  p. 
  600) 
  a 
  form 
  present 
  in 
  the 
  zone 
  of 
  Bel. 
  semicanalicu- 
  

   latus 
  ? 
  which 
  has 
  been 
  supposed 
  to 
  be 
  an 
  extreme 
  variety 
  of 
  this 
  

   species 
  ; 
  but 
  it 
  is 
  so 
  very 
  distinct 
  from 
  the 
  normal 
  type 
  that 
  I 
  think 
  

   it 
  deserves 
  to 
  rank 
  as 
  a 
  separate 
  species, 
  especially 
  as 
  it 
  does 
  not 
  

   occur 
  along 
  with 
  the 
  true 
  form. 
  

  

  One 
  variety 
  of 
  the 
  species 
  is 
  recognized 
  by 
  the 
  Russian 
  geologists 
  

   as 
  corresponding 
  to 
  their 
  Neocomian 
  form 
  Belemnites 
  Jasil'owi, 
  

   Lahus 
  *. 
  

  

  Belemnites 
  semicanaliculattjs 
  ? 
  

  

  I 
  have 
  already 
  mentioned 
  in 
  an 
  earlier 
  page 
  the 
  numerous 
  

   forms 
  of 
  the 
  genus 
  which 
  occur 
  in 
  the 
  upper 
  part 
  of 
  the 
  Speeton 
  

   section, 
  and 
  the 
  difficulties 
  connected 
  with 
  them. 
  They 
  have 
  not 
  

   yet 
  been 
  worked 
  up, 
  and 
  when 
  this 
  is 
  done 
  I 
  think 
  that 
  at 
  least 
  

   three 
  types, 
  and 
  probably 
  more, 
  will 
  be 
  recognized, 
  either 
  as 
  species 
  

   or 
  as 
  very 
  distinct 
  varieties. 
  By 
  far 
  the 
  commonest 
  form 
  is 
  the 
  one 
  

   which 
  was 
  first 
  doubtfully 
  assigned 
  by 
  Judd 
  to 
  Bel. 
  semicanaliculatus 
  

   (non 
  Blainville) 
  t, 
  and 
  afterwards 
  to 
  Bel. 
  bmnsvieensis, 
  Strom- 
  

   beck 
  J. 
  I 
  have 
  felt 
  the 
  inconvenience 
  of 
  denoting 
  a 
  zonal 
  division 
  

   by 
  the 
  name 
  of 
  a 
  doubtful 
  species, 
  but 
  cannot 
  see 
  how 
  to 
  avoid 
  

   doing 
  so, 
  as 
  I 
  have 
  not 
  been 
  able 
  to 
  find 
  any 
  other 
  plentiful 
  fossil 
  

   characteristic 
  of 
  the 
  whole 
  division. 
  I 
  have 
  therefore 
  applied 
  the 
  

   term 
  provisionally. 
  In 
  the 
  lower 
  part 
  of 
  the 
  zone 
  this 
  species 
  is 
  

   represented 
  by 
  a 
  rather 
  long 
  and 
  slender 
  variety 
  which 
  generally 
  

   shows 
  a 
  highly 
  polished 
  surface 
  ; 
  but 
  towards 
  the 
  top 
  of 
  the 
  divisiou 
  

   this 
  is 
  replaced 
  by 
  a 
  shorter 
  and 
  proportionately 
  thicker 
  form. 
  

   Neither 
  variety 
  is 
  grooved; 
  but 
  a 
  deeply 
  grooved 
  species 
  is 
  occa- 
  

  

  * 
  A. 
  Pavlow, 
  sup. 
  cit. 
  p. 
  41, 
  and 
  pi. 
  iii 
  ; 
  and 
  S. 
  Mkitin, 
  sup. 
  cit. 
  p. 
  42. 
  

  

  t 
  Op. 
  cit. 
  p. 
  245. 
  

  

  | 
  In 
  a 
  note 
  to 
  a 
  paper 
  by 
  T. 
  Davidson 
  in 
  Geol. 
  Mag. 
  vol. 
  vi. 
  p. 
  263. 
  

  

  