﻿102 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  surfaces 
  for 
  chevron 
  bones 
  were 
  much 
  narrowed 
  anterior 
  to 
  the 
  middle 
  of 
  series, 
  so 
  that 
  we 
  can 
  infer 
  that 
  the 
  tail 
  

   was 
  proximally 
  cylindrical. 
  Zygapophyses 
  turned 
  upward, 
  not 
  outward. 
  

  

  The 
  portions 
  of 
  the 
  three 
  sacrals 
  preserved 
  indicate 
  that 
  the 
  centrum 
  is 
  very 
  much 
  compressed, 
  as 
  in 
  other 
  Dino- 
  

   sauria. 
  The 
  proximal 
  caudals, 
  or 
  those 
  with 
  diapophyses, 
  have 
  also 
  compressed 
  centra, 
  though 
  this 
  is 
  less 
  marked 
  

   than 
  in 
  the 
  sacrals. 
  The 
  diapophyses 
  come 
  off 
  from 
  the 
  neural 
  arch 
  above 
  its 
  union 
  with 
  the 
  centrum 
  in 
  four 
  such 
  

   vertebra? 
  preserved. 
  In 
  these 
  the 
  arch 
  is 
  not 
  coossified. 
  In 
  the 
  remaining 
  nine 
  there 
  is 
  no 
  trace 
  of 
  diapophysis 
  

   beyond 
  a 
  ridge 
  visible 
  in 
  the 
  anterior 
  ones, 
  and 
  the 
  arches 
  are 
  coossified. 
  In 
  the 
  four 
  anterior 
  there 
  is 
  on 
  the 
  poste- 
  

   rior 
  half 
  of 
  the 
  median 
  line 
  below, 
  a 
  strong 
  groove 
  ; 
  in 
  the 
  two 
  median, 
  a 
  foramen 
  penetrates 
  the 
  centrum 
  ; 
  in 
  the 
  

   posterior 
  the 
  groove 
  is 
  less 
  posterior 
  in 
  its 
  position. 
  In 
  the 
  posterior 
  series 
  often 
  it 
  is 
  represented 
  by 
  an 
  indistinct 
  

   plane. 
  These 
  vertebrae 
  are 
  relatively 
  less 
  compressed 
  than 
  the 
  first, 
  but 
  have 
  a 
  more 
  concave 
  inferior 
  outline. 
  The 
  

   neural 
  spines 
  of 
  these 
  have 
  been 
  apparently 
  curved 
  upwards 
  and 
  backwards, 
  judging 
  from 
  the 
  direction 
  of 
  the 
  lines 
  

   of 
  ossific 
  growth, 
  as 
  in 
  Poecilopleurum. 
  They 
  originate 
  a 
  little 
  anterior 
  to 
  the 
  middle 
  of 
  the 
  length 
  of 
  the 
  vertebra. 
  

   Anterior 
  to 
  this 
  point 
  the 
  neural 
  canal 
  is 
  only 
  partially 
  roofed 
  over, 
  there 
  being 
  an 
  opening 
  into 
  it 
  just 
  in 
  front 
  of 
  the 
  

   base 
  of 
  the 
  neural 
  arch 
  . 
  Anteriorly 
  the 
  roof 
  would 
  appear 
  to 
  be 
  composed 
  by 
  the 
  union 
  of 
  two 
  horizontal 
  lamin.-e 
  of 
  

   the 
  anterior 
  zygapophyses. 
  The 
  articular 
  faces 
  for 
  chevron 
  bones 
  are 
  small. 
  

  

  Dimensions 
  of 
  an 
  anterior 
  caudal; 
  length 
  centrum, 
  

  

  depth 
  do. 
  from 
  suture 
  of 
  neural 
  arch, 
  

  

  width 
  articular 
  face 
  (anterior), 
  

   " 
  centrum 
  at 
  middle, 
  

   Length 
  of 
  median 
  caudal, 
  

   Breadth 
  centrum, 
  

   Length 
  base 
  neural 
  spine, 
  

   Length 
  of 
  a 
  distal 
  caudal 
  (with 
  neural 
  canal), 
  

   Diameter 
  centrum 
  transverse, 
  

  

  " 
  " 
  vertical, 
  

  

  Proximal 
  caudal 
  (with 
  short 
  diapophysis) 
  length, 
  

   Depth 
  centrum, 
  

   Width 
  " 
  

  

  Three 
  separate 
  vertebra 
  appear 
  to 
  be 
  most 
  probably 
  sacrals, 
  and 
  indicate 
  that 
  this 
  individual 
  was 
  not 
  adult. 
  

   Their 
  form 
  is 
  much 
  compressed, 
  and 
  the 
  articular 
  surfaces 
  are 
  rather 
  expanded 
  and 
  concave. 
  The 
  superficial 
  

   layer 
  of 
  the 
  latter 
  is 
  very 
  thin, 
  and 
  covered 
  with 
  delicate 
  raised 
  strim, 
  mostly 
  transverse 
  in 
  direction. 
  They 
  present 
  

   the 
  appearance 
  of 
  incomplete 
  development, 
  and 
  would 
  no 
  doubt 
  at 
  a 
  later 
  period 
  coossify 
  with 
  those 
  of 
  the 
  adjacent 
  

   vertebrre, 
  forming 
  the 
  long 
  sacrum 
  common 
  to 
  the 
  order. 
  Their 
  exterior 
  dense 
  walls 
  are 
  remarkably 
  thin, 
  and 
  the 
  

   internal 
  structure 
  of 
  the 
  centra 
  is 
  coarsely 
  spongy 
  or 
  almost 
  cavernous, 
  being 
  far 
  less 
  close 
  and 
  compact 
  than 
  that 
  of 
  

   the 
  cancellous 
  centra 
  of 
  the 
  caudals. 
  The 
  largest 
  of 
  these 
  has 
  a 
  strong 
  median 
  groove 
  above, 
  probably 
  that 
  of 
  the 
  

   neural 
  canal: 
  greatest 
  elevation 
  of 
  articular 
  surface 
  5 
  in. 
  2 
  lin., 
  greatest 
  width 
  of 
  same 
  4 
  in. 
  2 
  lin. 
  The 
  tissue 
  of 
  this 
  

   centrum 
  is 
  so 
  coarse 
  as 
  to 
  resemble 
  the 
  borings 
  of 
  Teredo. 
  In 
  another 
  a 
  large 
  foramen 
  marks 
  the 
  mouth 
  of 
  a 
  canal 
  

   which 
  enters 
  the 
  centrum 
  just 
  behind 
  one 
  of 
  the 
  articular 
  surfaces, 
  and 
  above 
  the 
  thickest 
  portion 
  of 
  the 
  centrum. 
  

   It 
  descends 
  obliquely 
  towards 
  the 
  middle 
  of 
  the 
  centrum, 
  but 
  its 
  course 
  can 
  be 
  traced 
  only 
  an 
  inch. 
  Foramen 
  .9 
  inch 
  

   in 
  diameter. 
  

  

  The 
  number 
  of 
  caudals 
  preserved 
  is 
  fourteen. 
  From 
  interruptions 
  in 
  the 
  series 
  I 
  imagine 
  that 
  ten 
  have 
  been 
  

   lost, 
  probably 
  a 
  few 
  more; 
  I 
  think 
  the 
  whole 
  number 
  can 
  be 
  estimated 
  at 
  twenty-five. 
  Both 
  distals 
  and 
  proximals 
  

   are 
  preserved; 
  the 
  former 
  are 
  small 
  and 
  slender, 
  the 
  latter 
  compressed, 
  similar 
  to 
  the 
  sacrals, 
  and 
  with 
  diapophysis, 
  

   and 
  neural 
  arch 
  not 
  coossified. 
  

  

  This 
  furnishes 
  a 
  remarkable 
  contrast 
  to 
  Hidrosaurus, 
  to 
  which 
  Leidy 
  reckons 
  fifty 
  vertebra*, 
  and 
  a 
  depth 
  of 
  

   tail 
  of 
  a 
  foot 
  and 
  a 
  half. 
  

  

  *They 
  thus 
  resemble 
  in 
  Reveral 
  ways, 
  the 
  bone 
  referred 
  by 
  Mantell 
  and 
  Owen 
  to 
  the 
  place 
  of 
  the 
  os 
  quadratum, 
  with 
  doubt. 
  There 
  is 
  little 
  probability 
  

   to 
  my 
  mind, 
  of 
  this 
  reference 
  proving 
  other" 
  than 
  erroneous; 
  see 
  the 
  fig 
  in 
  PI. 
  XI 
  at 
  the 
  end 
  of 
  the 
  volume. 
  

  

  In. 
  

  

  Lin, 
  

  

  4. 
  

  

  3 
  

  

  4.1 
  

  

  

  

  3. 
  

  

  G 
  

  

  2.56 
  

  

  

  

  4.G25 
  

  

  

  2.375 
  

  

  

  3.25 
  

  

  

  2.875 
  

  

  

  1.125 
  

  

  

  .875 
  

  

  

  4.5 
  

  

  

  3.125 
  

  

  

  3. 
  

  

  

  