﻿PROP. 
  H. 
  G. 
  SEELET 
  OX 
  THECOSPOXDYLTJS 
  HORNERI. 
  457 
  

  

  44. 
  On 
  Thecospoxdyltjs 
  Horneri, 
  a 
  new 
  Dinosaur 
  from 
  the 
  Hastings 
  

   Saitd, 
  indicated 
  by 
  the 
  Sacrum 
  and 
  the 
  JNeural 
  Canal 
  of 
  the 
  

   Sacral 
  Region. 
  By 
  Prof. 
  H. 
  G. 
  Seeley, 
  F.B.S., 
  F.G.S. 
  &c. 
  

   .(Read 
  June 
  21, 
  1882.) 
  

  

  [Plate 
  XIX.] 
  

  

  Dr. 
  A. 
  C. 
  Horner, 
  of 
  Tonbridge, 
  has 
  obtained 
  from 
  the 
  quarry 
  at 
  

   Southborough 
  in 
  the 
  Hastings 
  Sand, 
  and 
  intrusted 
  to 
  me, 
  what 
  I 
  

   believe 
  to 
  be 
  a 
  unique 
  specimen, 
  so 
  far 
  as 
  this 
  country 
  is 
  concerned, 
  

   exhibiting 
  a 
  mould 
  of 
  the 
  entire 
  neural 
  cavity 
  of 
  the 
  sacral 
  region 
  

   of 
  a 
  Dinosaur. 
  But 
  the 
  specimen 
  is 
  nevertheless 
  peculiarly 
  tan- 
  

   talizing, 
  since 
  the 
  quarryman 
  states 
  that 
  it 
  is 
  the 
  only 
  specimen 
  

   of 
  any 
  kind 
  that 
  he 
  has 
  ever 
  found 
  in 
  the 
  quarry, 
  and 
  enough 
  

   remains 
  of 
  bony 
  tissue 
  upon 
  the 
  cast 
  to 
  render 
  it 
  certain 
  that 
  the 
  

   external 
  mould 
  of 
  the 
  sacrum, 
  if 
  not 
  the 
  bony 
  tissue 
  itself, 
  might 
  

   have 
  been 
  preserved. 
  It 
  is 
  imperfect 
  both 
  anteriorly 
  and 
  posteriorly, 
  

   but 
  measures 
  exactly 
  60 
  centimetres 
  in 
  length. 
  The 
  vertebrae 
  

   which 
  are 
  complete 
  are 
  five 
  in 
  number 
  ; 
  each 
  is 
  11 
  centim. 
  long 
  ; 
  

   but 
  there 
  is 
  a 
  small 
  fragment 
  in 
  front 
  which 
  appears 
  to 
  show 
  that 
  

   there 
  was 
  another 
  vertebra 
  anteriorly 
  (fig. 
  2, 
  l), 
  while 
  the 
  fragment 
  of 
  

   the 
  posterior 
  vertebra 
  (fig. 
  2, 
  7) 
  admits 
  of 
  no 
  question. 
  We 
  have 
  thus 
  

   a 
  sacrum 
  which 
  certainly 
  included 
  six 
  or 
  seven 
  vertebras, 
  and 
  ma)- 
  

   have 
  comprised 
  more. 
  The 
  bony 
  tissue 
  is 
  preserved 
  only 
  upon 
  the 
  

   right 
  side 
  of 
  three 
  consecutive 
  vertebrae. 
  It 
  is 
  a 
  thin 
  film 
  closely 
  

   adherent 
  to 
  the 
  cast, 
  showing 
  a 
  cancellous 
  structure 
  external 
  to 
  the 
  

   thin 
  interior 
  layer 
  (fig. 
  1, 
  b). 
  This 
  film 
  is 
  not 
  more 
  than 
  from 
  1 
  to 
  

   2 
  millim. 
  in 
  thickness, 
  and 
  therefore 
  gives 
  no 
  clue 
  to 
  the 
  form 
  of 
  

   the 
  sacrum 
  ; 
  though 
  other 
  evidence 
  leads 
  me 
  to 
  believe 
  that 
  the 
  

   bone 
  was 
  extremely 
  thin, 
  and 
  pertained 
  to 
  an 
  animal 
  closely 
  allied 
  

   to 
  Ornithopsis. 
  

  

  The 
  neural 
  chamber 
  of 
  this 
  sacrum, 
  besides 
  being 
  remarkable 
  for 
  

   its 
  great 
  length, 
  is 
  singularly 
  compressed 
  from 
  side 
  to 
  side 
  (fig. 
  2), 
  and 
  

   expanded 
  from 
  below 
  upward 
  (fig. 
  1). 
  It 
  is 
  at 
  first 
  sight 
  no 
  easy 
  task 
  

   to 
  distinguish 
  the 
  back 
  from 
  the 
  front. 
  In 
  Anoplosaurus 
  curtonotus 
  

   I 
  figured 
  the 
  neural 
  canal 
  of 
  a 
  Dinosaur 
  (Quart. 
  Journ. 
  Geol. 
  Soc. 
  

   vol. 
  xxxv. 
  pi. 
  xxxiv.), 
  which 
  seemed 
  to 
  prove 
  that 
  the 
  anterior 
  third 
  

   of 
  the 
  neural 
  canal 
  is 
  the 
  part 
  which 
  has 
  the 
  greatest 
  transverse 
  

   expansion. 
  Subsequently 
  Prof. 
  Marsh 
  (Am. 
  Journ. 
  Sci. 
  vol. 
  xxi. 
  pi. 
  

   6, 
  1881) 
  figured 
  a 
  cast 
  of 
  the 
  neural 
  cavity 
  of 
  Stegosaurus, 
  in 
  which 
  

   the 
  sacral 
  canal 
  is 
  about 
  26 
  centim. 
  long, 
  and. 
  where 
  highest, 
  7*6 
  

   centim. 
  high, 
  and 
  4*3 
  centim. 
  wide 
  in 
  front. 
  

  

  Anoplosaurus 
  from 
  the 
  Cambridge 
  Greensand 
  had 
  the 
  sacral 
  

   nerves 
  of 
  moderate 
  size 
  ; 
  but 
  the 
  casts 
  of 
  the 
  foramina 
  between 
  the 
  

   vertebrae, 
  which 
  are 
  represented 
  in 
  Professor 
  Marsh's 
  plate, 
  are 
  deep 
  

   and 
  narrow, 
  and 
  two 
  of 
  them 
  extend 
  the 
  entire 
  height 
  of 
  the 
  neural 
  

   cavity. 
  In 
  regarding 
  the 
  larger 
  portion 
  of 
  the 
  sacrum 
  as 
  anterior, 
  we 
  

   follow 
  what 
  may 
  be 
  termed 
  Dinosaurian 
  precedents 
  : 
  and 
  when 
  we 
  

  

  Q.J.G.S. 
  No". 
  152. 
  2 
  1 
  

  

  