﻿Genus 
  Orbitoides 
  of 
  d* 
  Orbigny 
  . 
  213 
  

  

  the 
  margin, 
  the 
  cells 
  (stolonigerous 
  buds), 
  after 
  their 
  first 
  deve- 
  

   lopment, 
  breaking 
  into 
  each 
  other 
  so 
  generally 
  that 
  the 
  whole 
  

   is 
  thus 
  resolved 
  into 
  a 
  cancellated 
  structure 
  (calcareous 
  skele- 
  

   ton) 
  rilled 
  with 
  continuous 
  sarcode, 
  which 
  issues 
  into 
  the 
  cir- 
  

   cumambient 
  medium 
  by 
  the 
  way 
  mentioned, 
  as 
  in 
  such-like 
  

   Foraminifera. 
  Hence 
  this 
  structure 
  in 
  the 
  central 
  plane 
  of 
  

   Orbitolites 
  Mantelli. 
  

  

  Dr. 
  Carpenter, 
  in 
  his 
  admirable 
  " 
  Monograph 
  of 
  the 
  Genus 
  

   Orbitolites" 
  (Phil. 
  Trans. 
  1856, 
  p. 
  196, 
  pi. 
  vi. 
  fig. 
  5), 
  denies 
  

   the 
  presence 
  of 
  holes 
  in 
  the 
  " 
  shelly 
  substance 
  of 
  the 
  calca- 
  

   reous 
  disks 
  " 
  of 
  Orbitolites, 
  but 
  adds 
  that 
  the 
  " 
  punctated 
  

   marking"" 
  here 
  " 
  may 
  be 
  regarded 
  as 
  the 
  rudiments 
  of 
  those 
  

   minute 
  closely-set 
  apertures 
  which 
  in 
  many 
  Foraminifera 
  give 
  

   passage 
  to 
  pseudopodial 
  extensions 
  of 
  the 
  sarcode." 
  Whether 
  

   this 
  is 
  the 
  case 
  or 
  not 
  I 
  cannot 
  say 
  ; 
  but 
  where 
  the 
  holes 
  

   in 
  the 
  cells 
  are 
  manifest 
  they 
  are 
  situated 
  respectively 
  on 
  

   little 
  tubercles 
  as 
  in 
  other 
  Foraminifera. 
  

  

  The 
  holes 
  seen 
  in 
  the 
  cell-divisions 
  of 
  Orbitoides 
  media, 
  

   d'Orb., 
  in 
  a 
  mounted 
  microscopic 
  horizontal 
  section 
  of 
  the 
  

   erust 
  are 
  merely 
  transverse 
  sections 
  of 
  the 
  minute 
  tubuli 
  which 
  

   extend 
  perpendicularly 
  from 
  one 
  cell 
  to 
  another; 
  and 
  even 
  these 
  

   are 
  not 
  visible 
  on 
  the 
  surface 
  of 
  Orbitolites 
  Mantelli 
  from 
  

   Alabama, 
  where 
  the 
  cellular 
  structure 
  is 
  finally 
  covered 
  in 
  by 
  a 
  

   thin 
  film 
  of 
  ? 
  imperforate 
  homogeneous 
  shell-substance. 
  While 
  

   in 
  the 
  fossilized 
  Orbitolite 
  from 
  the 
  neighbourhood 
  of 
  Jarrak, 
  

   in 
  Lower 
  Sind, 
  &c, 
  which 
  1 
  have 
  designated 
  " 
  pedunculata 
  " 
  

   (' 
  Annals,' 
  1861, 
  vol. 
  viii. 
  p. 
  463, 
  and 
  delineated 
  in 
  that 
  of 
  

   1853, 
  vol. 
  ii. 
  pi. 
  vii. 
  figs. 
  43-45), 
  the 
  peduncle 
  or 
  papillary 
  

   eminence 
  is 
  formed 
  of 
  shell-substance, 
  from 
  which 
  sinuous 
  

   ridges 
  are 
  extended 
  to 
  the 
  circumference 
  in 
  the 
  same 
  way 
  as 
  

   that 
  represented 
  by 
  d'Orbigny 
  in 
  his 
  illustrations 
  of 
  Orbi- 
  

   toides 
  media 
  (op. 
  et 
  loc. 
  cit.). 
  J 
  have 
  already 
  alluded 
  to 
  this 
  

   structure 
  in 
  the 
  'Annals 
  ' 
  of 
  1861 
  {I. 
  c). 
  

  

  So 
  that 
  altogether, 
  part 
  for 
  part, 
  we 
  have 
  the 
  same 
  struc- 
  

   tures 
  in 
  Orbitolites 
  media 
  as 
  in 
  Orbitolites 
  marginalis, 
  saving 
  

   the 
  " 
  crust," 
  and 
  hence 
  the 
  reason 
  for 
  retaining 
  the 
  term 
  

   " 
  Orbitolites 
  " 
  in 
  generic 
  distinction. 
  

  

  Let 
  us 
  now, 
  in 
  conclusion, 
  direct 
  our 
  attention 
  more 
  parti- 
  

   cularly 
  than 
  1 
  have 
  hitherto 
  done 
  to 
  the 
  structure 
  of 
  this 
  

   " 
  crust," 
  for, 
  looking 
  at 
  it 
  in 
  the 
  vertical 
  section, 
  it 
  is 
  seen 
  to 
  

   be 
  composed 
  of 
  columns 
  of 
  vertically 
  compressed 
  cells, 
  which 
  

   are 
  arranged 
  more 
  or 
  less 
  perpendicularly 
  according 
  to 
  their 
  

   position 
  on 
  each 
  side 
  of 
  the 
  central 
  plane, 
  in 
  such 
  a 
  manner 
  as 
  

   to 
  lead 
  to 
  the 
  inference 
  that 
  they 
  are 
  a 
  direct 
  prolongation 
  

   vertically 
  of 
  the 
  spheroidal 
  ones 
  whose 
  regular 
  arrangement 
  

   in 
  the 
  central 
  plane, 
  when 
  viewed 
  horizontally, 
  gives 
  rise 
  to 
  

  

  