﻿94 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  the 
  most 
  contracted. 
  The 
  wide 
  caudals 
  continue 
  without 
  contraction 
  to 
  the 
  point 
  where 
  

   the 
  tail 
  reaches 
  the 
  ground. 
  They 
  then 
  begin 
  to 
  elongate. 
  The 
  anterior 
  vertebras 
  thus 
  

   form 
  a 
  massive 
  column, 
  which 
  no 
  doubt 
  supported 
  the 
  weight 
  of 
  these 
  monsters. 
  That 
  

   the 
  ischia 
  performed 
  this 
  function 
  in 
  part 
  in 
  Lselaps, 
  is 
  evident 
  not 
  only 
  from 
  their 
  more 
  

   massive 
  structure, 
  but 
  from 
  the 
  more 
  elongate 
  caudal 
  vertebrae, 
  while 
  the 
  still 
  more 
  slender 
  

   caudals 
  in 
  the 
  known 
  Triassic 
  genera, 
  adds 
  to 
  the 
  evidence 
  derived 
  from 
  the 
  ischia 
  as 
  to 
  

   their 
  use. 
  

  

  In 
  the 
  ilium 
  of 
  Hadrosaurus 
  the 
  slender 
  hooked 
  process 
  and 
  the 
  expanded 
  tuberosity 
  

   both 
  exist, 
  and 
  I 
  am 
  disposed 
  to 
  place 
  the 
  former 
  posteriorly, 
  and 
  the 
  latter 
  anteriorly 
  

   and 
  externally 
  as 
  the 
  most 
  probably 
  correct 
  relation. 
  This, 
  moreover, 
  throws 
  posterior 
  to 
  

   the 
  acetabulum, 
  the 
  more 
  elongate 
  articular 
  face, 
  where 
  one 
  might 
  look 
  for 
  the 
  ischiadic 
  

   suture 
  with 
  propriety. 
  This 
  arrangement, 
  however, 
  presents 
  the 
  apparent 
  anomaly 
  of 
  

   position, 
  that 
  the 
  planes 
  of 
  the 
  inner 
  faces 
  of 
  the 
  ilia 
  are 
  made 
  to 
  converge 
  instead 
  of 
  di- 
  

   verge, 
  thus 
  rendering 
  the 
  interiliac 
  cavity 
  remarkably 
  narrow. 
  There 
  can, 
  however, 
  be 
  

   no 
  doubt 
  that 
  this 
  is 
  really 
  their 
  position 
  in 
  Iguanodon, 
  judging 
  from 
  Owen's 
  figures 
  

   (above), 
  III. 
  and 
  IV., 
  and 
  that 
  the 
  sacral 
  diapophyses 
  really 
  rest 
  on 
  the 
  convergent 
  faces 
  

   of 
  the 
  ilia, 
  whose 
  planes 
  are 
  directed 
  inwards 
  as 
  well 
  as 
  downwards. 
  This 
  adds 
  still 
  fur- 
  

   ther 
  to 
  the 
  peculiar 
  ensemble 
  of 
  characters 
  of 
  these 
  Dinosauria. 
  

  

  This 
  relation 
  has 
  already 
  been 
  described 
  as 
  the 
  true 
  one, 
  by 
  Leidy. 
  

  

  The 
  anterior 
  prolongation 
  of 
  the 
  ilium 
  in 
  Hadrosaurus 
  appears 
  to 
  be 
  less 
  slender 
  and 
  

   more 
  plate-like 
  than 
  in 
  Iguanodon 
  and 
  Scelidosaurus, 
  where 
  it 
  is 
  remarkably 
  produced. 
  

   Nevertheless, 
  in 
  the 
  accompanying 
  cut, 
  the 
  restoration 
  (by 
  Dr. 
  Horn) 
  of 
  the 
  anterior 
  por- 
  

   tion 
  may 
  be 
  too 
  much 
  dilated, 
  and 
  is 
  probably 
  not 
  long 
  enough. 
  

  

  Pubis. 
  This 
  element 
  of 
  Hadrosaurus 
  has 
  never 
  been 
  described. 
  I 
  believe 
  that 
  I 
  find 
  

   it 
  in 
  a 
  proximal 
  portion 
  of 
  a 
  large 
  bone, 
  which 
  occupies 
  this 
  relation 
  very 
  appropriately. 
  

   Its 
  proximal 
  superior 
  subtriangular 
  articular 
  face 
  is 
  naturally 
  associated 
  with 
  the 
  already 
  

   assumed 
  anterior 
  articulation 
  of 
  the 
  ilium, 
  and 
  when 
  so 
  placed, 
  presents 
  outwards 
  the 
  

   smooth 
  articular 
  surface 
  of 
  the 
  anterior 
  part 
  of 
  the 
  acetabulum. 
  It 
  also 
  presents 
  forwards 
  

   a 
  narrowed 
  process, 
  and 
  in 
  line 
  with 
  the 
  same 
  posteriorly, 
  a 
  broad, 
  vertical 
  plate 
  which 
  is 
  

   soon 
  broken 
  off, 
  but 
  which 
  I 
  suppose 
  to 
  have 
  been 
  continued 
  but 
  a 
  short 
  distance. 
  The 
  

   posterior 
  process 
  I 
  suppose 
  has 
  been 
  continued 
  as 
  the 
  support 
  of 
  a 
  slender 
  pubis,* 
  conform- 
  

   ing 
  in 
  this 
  respect 
  to 
  the 
  type 
  of 
  birds. 
  That 
  there 
  is 
  very 
  little 
  trace 
  of 
  articulation 
  for 
  

   ischium 
  behind 
  the 
  acetabulum 
  is 
  obvious, 
  so 
  that 
  it 
  is 
  to 
  be 
  supposed 
  that 
  this 
  element 
  

   was 
  small, 
  vertically 
  dilated 
  proximally, 
  and 
  in 
  contact 
  with 
  the 
  pubis 
  at 
  the 
  superior 
  

   processes 
  on 
  the 
  supero-external 
  margin 
  of 
  the 
  latter. 
  

  

  * 
  A 
  suspicion 
  which 
  I 
  at 
  one 
  time 
  entertained, 
  that 
  the 
  so-called 
  pubis 
  of 
  the 
  Crocodilia 
  was 
  homologous 
  with 
  

   the 
  marsupial 
  bones, 
  has 
  been 
  removed, 
  by 
  reading 
  Rathke's 
  posthumous 
  work 
  on 
  the 
  development 
  of 
  the 
  Crocodile. 
  

  

  