﻿crick: 
  on 
  GLYPlIIOCEnAS 
  VESICULIFKRIJM. 
  51 
  

  

  C, 
  composite 
  figure 
  of 
  the 
  ventral 
  portion 
  of 
  the 
  septal 
  suture, 
  formed 
  by 
  

   combining 
  Figs. 
  A 
  and 
  B, 
  the 
  dotted 
  portion 
  being 
  supplied. 
  

  

  D, 
  the 
  dorsal 
  portion 
  of 
  the 
  septal 
  suture. 
  

  

  Drawn 
  from 
  a 
  specimen 
  in 
  the 
  collection 
  of 
  Dr. 
  Wheelton 
  Hind, 
  from 
  the 
  

   Carboniferous 
  Limestone 
  of 
  Elbolton, 
  near 
  Cracoe, 
  Yorkshire, 
  figured 
  in 
  

   Proe. 
  Yorkshire 
  Geol. 
  Soc, 
  vol. 
  xvii, 
  part 
  2, 
  1910, 
  pi. 
  vi, 
  figs. 
  2, 
  2rt, 
  2o. 
  

  

  Fi(i. 
  2. 
  — 
  Reproduction 
  of 
  de 
  Koninck's 
  figui"e 
  of 
  the 
  septal 
  suture 
  of 
  his 
  

   froniatites 
  resiculifer. 
  

  

  Fkj. 
  ii. 
  — 
  Ghipliioccras 
  sphcericum 
  {\N 
  . 
  Martin). 
  

  

  A, 
  ventral 
  and 
  lateral 
  portions 
  of 
  a 
  septal 
  suture, 
  x 
  f 
  . 
  

  

  B, 
  the 
  dorsal 
  portion 
  of 
  a 
  septal 
  suture, 
  x 
  J. 
  For 
  comijarison 
  with 
  

   Fig. 
  1, 
  C 
  and 
  D. 
  

  

  Drawn 
  from 
  the 
  example, 
  from 
  the 
  Carboniferous 
  Limestone 
  of 
  Derby- 
  

   shire, 
  figured 
  by 
  J. 
  Howerby, 
  Min. 
  Conch., 
  vol. 
  i 
  (part 
  10, 
  April, 
  1814), 
  

   p. 
  116, 
  pi. 
  liii, 
  fig. 
  2, 
  now 
  in 
  the 
  British 
  Museum 
  collection 
  [no. 
  43871]. 
  

  

  In 
  all 
  the 
  figures 
  el 
  = 
  external 
  (or 
  ventral) 
  lobe 
  ; 
  es 
  ~ 
  external 
  saddle 
  ; 
  

   iZ 
  = 
  internal 
  (dorsal, 
  columeliar 
  or 
  antisiphonal) 
  lobe 
  ; 
  i/Z 
  = 
  internal 
  lateral 
  

   lobe 
  ; 
  Us 
  = 
  internal 
  lateral 
  saddle 
  ; 
  is 
  = 
  internal 
  (or 
  dorsal) 
  saddle 
  ; 
  

   /.s== 
  lateral 
  saddle 
  ; 
  7H.s 
  = 
  median 
  lor 
  siphonal) 
  saddle 
  ; 
  .s 
  marks 
  the 
  position 
  

   of 
  the 
  suture 
  of 
  the 
  shell 
  ; 
  and 
  n 
  indicates 
  tlie 
  position 
  of 
  the 
  margin 
  of 
  

   the 
  umbilicus. 
  The 
  arrow 
  marks 
  the 
  median 
  line 
  of 
  the 
  peripheral 
  area 
  

   and 
  points 
  toward 
  the 
  aperture. 
  

  

  There 
  is 
  also 
  au 
  example 
  in 
  the 
  Britisli 
  Museum 
  Collection 
  [Geol. 
  

   Dept., 
  register 
  no. 
  C. 
  18509], 
  but 
  unfortunately 
  the 
  locality 
  is 
  

   unrecorded. 
  It 
  is 
  much 
  snuiUer 
  than 
  Dr. 
  Hind's 
  example, 
  being 
  only 
  

   12"5 
  mm. 
  in 
  diameter. 
  It 
  is 
  well 
  preserved, 
  though 
  incomplete, 
  

   being 
  composed 
  of 
  only 
  the 
  septated 
  part 
  of 
  the 
  shell. 
  On 
  the 
  

   peripliery 
  of 
  the 
  youngest 
  part 
  of 
  the 
  last 
  whorl, 
  immediately 
  in 
  

   front 
  of 
  the 
  present 
  anterior 
  end 
  of 
  the 
  specimen, 
  the 
  dorsal 
  edge 
  

   of 
  the 
  last 
  septum 
  is 
  clearly 
  seen, 
  sliowing 
  that 
  the 
  specimen 
  

   lacks 
  the 
  whole 
  of 
  the 
  body-chamber. 
  The 
  longitudinal 
  vesicular 
  

   ridges 
  are 
  quite 
  prominent, 
  extending 
  on 
  one 
  side 
  of 
  the 
  sliell 
  

   over 
  the 
  Avhole 
  length 
  of 
  the 
  outer 
  whorl 
  and 
  on 
  the 
  other 
  side 
  

   to 
  within 
  a 
  short 
  distance 
  of 
  the 
  anterior 
  end 
  of 
  the 
  specimen, 
  

   being 
  highest 
  at 
  the 
  commencement 
  of 
  the 
  whorl 
  and 
  gradually 
  

   decreasing 
  in 
  passing 
  forwards, 
  until 
  near 
  the 
  anterior 
  end 
  eacli 
  

   becomes 
  little 
  more 
  than 
  a 
  relatively 
  coarse 
  meshwork 
  on 
  the 
  

   periphero-lateral 
  surface 
  of 
  the 
  specimen. 
  On 
  the 
  peripheral 
  side 
  

   each 
  vesicular 
  ridge 
  passes 
  into 
  somewhat 
  coarse 
  transverse 
  rugae, 
  

   which 
  soon 
  become 
  very 
  indistinct, 
  and 
  in 
  turn 
  pass 
  into 
  exceedingly 
  

   fine 
  transverse 
  lines 
  which 
  occupy 
  the 
  greater 
  part 
  of 
  the 
  median 
  

   area; 
  whilst 
  on 
  the 
  umbilical 
  side 
  each 
  ridge 
  passes 
  into 
  very 
  fine 
  

   rugae, 
  tlie 
  whole 
  of 
  the 
  lateral 
  area 
  being 
  crossed 
  also 
  by 
  exceedingly 
  

   fine 
  longitudinal 
  lines, 
  imparting 
  to 
  this 
  portion 
  of 
  the 
  fossil 
  a 
  very 
  

   fine 
  cancellated 
  appearance. 
  The 
  portions 
  of 
  the 
  peripheral 
  area 
  

   adjacent 
  to 
  the 
  vesicular 
  bands 
  bear 
  also 
  extremely 
  fine 
  longitudinal 
  

   lines, 
  which 
  at 
  the 
  anterior 
  end 
  of 
  the 
  specimen 
  seem 
  to 
  pass 
  beneath 
  

   the 
  vesicular 
  band, 
  and 
  to 
  be 
  lacking 
  on 
  the 
  median 
  portion 
  of 
  this 
  area. 
  

   The 
  surface 
  of 
  the 
  anterior 
  end 
  of 
  the 
  specimen 
  bears 
  exceedingly 
  fine 
  

   growth-lines, 
  which 
  have 
  an 
  almost 
  radial 
  direction 
  on 
  the 
  inner 
  half 
  

   of 
  the 
  whorl, 
  form 
  a 
  sliallow 
  sinus 
  on 
  the 
  outer 
  half, 
  au 
  obtuse 
  crest 
  

  

  