﻿J. 
  W. 
  HITLKE 
  OX 
  THE 
  AX 
  ATOMY 
  OF 
  HYPSILOPHODOX 
  FOXII. 
  21 
  

  

  precede 
  the 
  sacrum 
  and 
  cannot 
  follow 
  it 
  ; 
  the 
  sixth 
  vertebra 
  must 
  

   in 
  fine 
  be 
  the 
  last 
  lumbar. 
  

  

  The 
  length 
  of 
  this 
  centrum 
  is 
  rather 
  less 
  than 
  '9 
  inch, 
  the 
  same 
  

   as 
  that 
  of 
  the 
  fifth 
  and 
  fourth 
  centra. 
  Its 
  form 
  is 
  cylindric, 
  its 
  

   contour 
  transversely 
  convex, 
  and 
  longitudinally 
  hollow, 
  tbe 
  middle 
  

   slightly 
  contracted 
  and 
  the 
  ends 
  swollen, 
  particularly 
  that 
  which 
  is 
  

   anchylosed 
  to 
  the 
  first 
  sacral. 
  Its 
  transverse 
  diameter 
  at 
  its 
  middle 
  

   is 
  -6 
  inch, 
  at 
  its 
  front 
  end 
  "8, 
  and 
  at 
  its 
  posterior 
  end 
  somewhat 
  

   more. 
  The 
  transverse 
  processes 
  of 
  the 
  second, 
  third, 
  and 
  fourth 
  

   lumbar 
  vertebrae 
  have 
  slender 
  ribs 
  anchylosed 
  to 
  their 
  extremities, 
  

   a 
  distinct 
  knot 
  marks 
  the 
  union 
  of 
  dia- 
  and 
  pleurapophysis. 
  They 
  

   differ 
  in 
  this 
  respect 
  from 
  the 
  corresponding 
  vertebra? 
  in 
  the 
  Alligator 
  

   (A. 
  lucius) 
  and 
  other 
  existing 
  crocodilians, 
  in 
  which 
  the 
  traces 
  of 
  

   the 
  primitive 
  separateness 
  of 
  the 
  transverse 
  process 
  and 
  rib 
  disappear 
  

   with 
  the 
  maturity 
  of 
  the 
  individual. 
  

  

  The 
  determination 
  of 
  the 
  first 
  lumbar 
  carries 
  with 
  it 
  that 
  of 
  the 
  

   next 
  succeeding 
  vertebra, 
  it 
  is 
  the 
  first 
  sacral 
  (1 
  s.) 
  ; 
  we 
  have 
  then 
  

   the 
  first, 
  and 
  not 
  the 
  posterior 
  moiety 
  of 
  the 
  sacrum. 
  The 
  first 
  and 
  

   second 
  sacral 
  centra 
  are 
  much 
  smaller 
  than 
  the 
  last 
  lumbar, 
  a 
  

   similar 
  difference 
  of 
  bulk 
  obtains 
  in 
  the 
  sacrum 
  assigned 
  to 
  Iguanodon 
  

   Mantelli 
  ; 
  but 
  this 
  difference 
  does 
  not 
  extend 
  to 
  their 
  figure, 
  which 
  

   has 
  a 
  general 
  resemblance 
  to 
  that 
  of 
  the 
  lumbar 
  vertebrae. 
  It 
  too 
  

   is 
  cylindroid, 
  constricted 
  at 
  the 
  middle 
  and 
  expanded 
  at 
  its 
  end, 
  

   which 
  gives 
  the 
  lower 
  contour 
  of 
  the 
  chain 
  a 
  sinuous 
  outline, 
  hollow 
  

   at 
  the 
  middle 
  of 
  the 
  centra 
  and 
  convex 
  at 
  their 
  coalesced 
  extremities. 
  

   The 
  swelling 
  which 
  marks 
  the 
  junction 
  of 
  the 
  coalesced 
  centra 
  is 
  

   not 
  a 
  uniformly 
  tumid 
  nodal 
  ring 
  ; 
  but 
  it 
  is 
  greatest 
  at 
  the 
  union 
  of 
  

   the 
  sides 
  and 
  inferior 
  surface, 
  forming 
  here 
  a 
  pair 
  of 
  small 
  elevations 
  

   similar 
  to 
  those 
  in 
  the 
  reputed 
  sacra 
  of 
  Iguanodon 
  Mantelli 
  and 
  

   Hylceosaurus. 
  The 
  transverse 
  process 
  of 
  the 
  first 
  sacral 
  vertebra 
  

   springs 
  from 
  the 
  junction 
  of 
  this 
  vertebra 
  with 
  the 
  last 
  lumbar, 
  

   standing 
  out 
  from 
  here 
  vertically 
  to 
  the 
  axis 
  of 
  the 
  sacrum. 
  It 
  is 
  

   remarkably 
  stout, 
  the 
  antero-posterior 
  diameter 
  of 
  its 
  root 
  is 
  - 
  6 
  

   inch 
  ; 
  its 
  anterior 
  contour 
  merges 
  into 
  the 
  lateral 
  contour 
  of 
  the 
  last 
  

   lumbar 
  centrum, 
  greatly 
  increasing 
  the 
  apparent 
  bulk 
  of 
  this. 
  At 
  - 
  5 
  

   inch 
  distance 
  from 
  its 
  origin, 
  it 
  bends 
  backwards 
  nearly 
  at 
  a 
  right 
  angle 
  

   to 
  its 
  first 
  direction, 
  and 
  joins 
  the 
  dilated 
  outer 
  end 
  of 
  the 
  second 
  

   transverse 
  process 
  springing 
  from 
  the 
  union 
  of 
  the 
  second 
  and 
  first 
  

   centra, 
  and 
  it 
  includes 
  with 
  this 
  a 
  large 
  subcircular 
  loop. 
  A 
  third 
  

   transverse 
  process 
  in 
  like 
  manner 
  abuts 
  on 
  the 
  junction 
  of 
  the 
  third 
  

   and 
  second 
  sacral 
  centres, 
  and 
  from 
  two 
  of 
  the 
  loops 
  with 
  the 
  second 
  

   and 
  fourth 
  transverse 
  processes, 
  making 
  in 
  all 
  three 
  of 
  those 
  loops 
  

   or 
  nerve-foramina 
  ; 
  but 
  the 
  third 
  and 
  fourth 
  centra 
  are 
  missing, 
  the 
  

   third 
  having 
  been 
  broken 
  off 
  just 
  behind 
  its 
  union 
  with 
  the 
  second. 
  

   Against 
  the 
  strong 
  buttress 
  formed 
  by 
  the 
  confluent 
  dilated 
  ends 
  of 
  

   the 
  transverse 
  processes 
  on 
  the 
  right 
  side 
  lies 
  a 
  fragment 
  of 
  the 
  

   right 
  ileum 
  {II.). 
  

  

  Below 
  this 
  chain 
  of 
  vertebrae 
  lies 
  a 
  second 
  chain 
  of 
  seven 
  

   smaller 
  vertebrae 
  with 
  part 
  of 
  a 
  sacrum 
  including 
  four 
  centra. 
  It 
  

   appeared 
  so 
  unlikely 
  that 
  this 
  should 
  be 
  part 
  of 
  the 
  spinal 
  column 
  

  

  