﻿204 
  H. 
  G. 
  SEELEY 
  ON 
  HTTR^NOSATJRTTS 
  LEEDSII, 
  

  

  the 
  neural 
  arch 
  is 
  inclined 
  very 
  slightly 
  backward. 
  Beyond 
  this 
  

   vertebra, 
  which 
  is 
  the 
  middle 
  of 
  the 
  back, 
  the 
  vertebrae 
  get 
  gradu- 
  

   ally 
  smaller, 
  and 
  the 
  neural 
  spines 
  shorten, 
  though 
  they 
  retain 
  their 
  

   breadth. 
  The 
  sixteenth 
  dorsal 
  has 
  the 
  centrum 
  1-| 
  inch 
  long, 
  and 
  

   measures 
  6| 
  inches 
  from 
  the 
  base 
  of 
  the 
  centrum 
  to 
  the 
  top 
  of 
  the 
  

   neural 
  spine 
  ; 
  the 
  position 
  of 
  the 
  transverse 
  processes 
  remains 
  un- 
  

   changed, 
  but 
  the 
  base 
  of 
  the 
  pedicle 
  has 
  become 
  shorter 
  from 
  front 
  to 
  

   back, 
  and 
  is 
  rhomboidal 
  in 
  section. 
  

  

  Pelvic 
  Vertebrce. 
  

  

  The 
  neural 
  arch 
  is 
  not 
  preserved 
  in 
  the 
  pelvic 
  or 
  sacral 
  vertebrae, 
  

   and 
  the 
  form 
  of 
  the 
  centrum 
  is 
  modified 
  in 
  consequence 
  of 
  the 
  

   descending 
  position 
  of 
  the 
  transverse 
  process. 
  The 
  two 
  middle 
  pelvic 
  

   vertebra? 
  appear 
  to 
  have 
  the 
  centrum 
  shorter 
  from 
  back 
  to 
  front 
  than 
  

   the 
  others, 
  measuring 
  only 
  1| 
  inch. 
  The 
  articular 
  surface 
  of 
  the 
  

   centrum 
  appears 
  to 
  be 
  somewhat 
  depressed 
  from 
  above 
  downward, 
  

   and 
  to 
  be 
  more 
  concave 
  than 
  in 
  the 
  dorsal 
  region, 
  while 
  the 
  under- 
  

   side 
  is 
  less 
  convex 
  from 
  side 
  to 
  side. 
  The 
  transverse 
  process 
  is 
  

   strong, 
  and 
  subquadrate 
  where 
  broken 
  off 
  at 
  the 
  base. 
  In 
  the 
  last 
  

   pelvic 
  vertebra 
  the 
  transverse 
  process 
  appears 
  to 
  have 
  been 
  much 
  

   larger 
  than 
  in 
  the 
  others, 
  and 
  to 
  have 
  come 
  away 
  from 
  the 
  centrum 
  

   by 
  a 
  sutural 
  surface 
  1^ 
  inch 
  deep 
  by 
  1^ 
  inch 
  wide, 
  which 
  stands 
  up 
  

   from 
  the 
  centrum 
  with 
  an 
  elevated 
  margin. 
  

  

  Caudal 
  Vertebrce. 
  

  

  In 
  the 
  next 
  three 
  vertebras 
  the 
  caudal 
  rib 
  has 
  descended 
  to 
  the 
  

   side 
  of 
  the 
  centrum, 
  and 
  is 
  marked 
  by 
  a 
  large 
  thick 
  fragment 
  of 
  a 
  

   rib, 
  which 
  appears 
  to 
  have 
  been 
  anchylosed 
  to 
  the 
  centrum. 
  These 
  

   vertebrae 
  are 
  less 
  than 
  1| 
  inch 
  long, 
  and 
  have 
  the 
  articular 
  centrum- 
  

   margins 
  bevelled 
  as 
  in 
  the 
  neck. 
  As 
  in 
  the 
  pelvic 
  region, 
  the 
  neural 
  

   arch 
  rises 
  from 
  a 
  more 
  anterior 
  part 
  of 
  the 
  centrum 
  than 
  is 
  the 
  

   case 
  with 
  the 
  dorsal 
  vertebras, 
  and 
  is 
  shorter 
  from 
  back 
  to 
  front. 
  The 
  

   third 
  caudal 
  has 
  the 
  neural 
  arch 
  preserved, 
  and 
  shows 
  that 
  the 
  

   zygapophysial 
  facets 
  still 
  retain 
  their 
  quarter-cylinder 
  form 
  : 
  the 
  

   extreme 
  height 
  from 
  the 
  base 
  of 
  the 
  centrum 
  to 
  the 
  top 
  of 
  the 
  neural 
  

   spine 
  is 
  5 
  inches. 
  The 
  neural 
  spine 
  is 
  directed 
  backward, 
  and 
  tapers 
  

   from 
  below 
  upward, 
  where 
  it 
  is 
  rather 
  more 
  than 
  an 
  inch 
  from 
  back 
  

   to 
  front, 
  and 
  is 
  somewhat 
  expanded 
  from 
  side 
  to 
  side 
  at 
  its 
  superior 
  

   termination. 
  

  

  The 
  fifth 
  caudal 
  (fig. 
  5) 
  is 
  the 
  first 
  which 
  gives 
  indications 
  of 
  a 
  

   chevron 
  bone, 
  and 
  that 
  only 
  on 
  the 
  left 
  side. 
  The 
  facets 
  for 
  these 
  

   bones 
  in 
  the 
  succeeding 
  vertebrae 
  are 
  singularly 
  large 
  and 
  elevated, 
  

   and 
  somewhat 
  triangular 
  in 
  form. 
  They 
  raise 
  the 
  side 
  of 
  the 
  centrum 
  

   near 
  them, 
  and 
  are 
  so 
  placed 
  that 
  the 
  chevron 
  bones 
  attached 
  to 
  them 
  

   never 
  impress 
  the 
  articular 
  surface 
  of 
  the 
  succeeding 
  vertebrae 
  (fig. 
  4), 
  

   in 
  this 
  differing 
  from 
  Plesiosaurus 
  and 
  recalling 
  Mosasaurus. 
  In 
  

   the 
  fifth 
  caudal 
  the 
  centrum 
  is 
  1| 
  inch 
  from 
  front 
  to 
  back, 
  1^ 
  inch 
  

   from 
  side 
  to 
  side, 
  and 
  1| 
  inch 
  from 
  above 
  downward. 
  As 
  in 
  all 
  the 
  

   other 
  vertebras, 
  the 
  posterior 
  measurement 
  is 
  slightly 
  longer 
  than 
  the 
  

   anterior 
  measurement. 
  The 
  articular 
  margins 
  do 
  not 
  stand 
  up 
  from 
  

  

  