﻿96 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  Owen 
  in 
  Iguanodon 
  Avith 
  clavicles, 
  and 
  by 
  Leidy 
  in 
  Hadrosaurus 
  with 
  the 
  pubes. 
  The 
  

   Director 
  in 
  the 
  British 
  Museum 
  has 
  well 
  pointed 
  out 
  the 
  possibility 
  of 
  such 
  a 
  form 
  of 
  

   clavicle 
  being 
  probable, 
  after 
  a 
  comprehension 
  of 
  the 
  variations 
  presented 
  by 
  the 
  modern 
  

   Sauria, 
  and 
  the 
  not 
  dissimilar 
  form 
  in 
  Trachysaurus 
  and 
  Cyclodus. 
  Leidy, 
  however, 
  is 
  of 
  

   opinion 
  that 
  similar 
  bones 
  in 
  Hadrosaurus 
  resemble 
  rather 
  the 
  pubic 
  bones 
  of 
  Iguana, 
  and 
  

   calls 
  them 
  pubes, 
  with 
  doubt. 
  The 
  writer 
  sees 
  a 
  much 
  greater 
  resemblance 
  between 
  them 
  

   and 
  the 
  elements 
  called 
  ischia 
  by 
  Wagner 
  in 
  the 
  Compsognathus, 
  and 
  which 
  are 
  homolo- 
  

   gous 
  with 
  the 
  posteriorly 
  directed 
  bone 
  so 
  called 
  in 
  birds. 
  

  

  It 
  is 
  noticeable 
  that 
  in 
  the 
  great 
  Dinosauria 
  the 
  supposed 
  clavicles 
  do 
  not 
  diminish 
  in 
  

   length 
  in 
  the 
  same 
  proportion 
  as 
  do 
  the 
  humeri, 
  as 
  one 
  would 
  be 
  led 
  to 
  expect 
  were 
  they 
  

   clavicles. 
  The 
  relative 
  lengths 
  in 
  three 
  species 
  are 
  as 
  follows 
  : 
  — 
  

  

  Inches. 
  

  

  Iguanodon 
  anglicus 
  ; 
  humerus, 
  35. 
  

  

  os 
  ischium, 
  29. 
  

  

  Hadrosaurus 
  foulkii 
  ; 
  humerus, 
  22.5 
  

  

  os 
  ischium, 
  27. 
  

  

  Laelaps 
  aquilunguis; 
  humerus, 
  12. 
  

  

  os 
  ischium, 
  20. 
  

  

  Their 
  density 
  and 
  strength 
  in 
  the 
  last 
  named 
  species 
  are 
  not 
  readily 
  reconcilable 
  with 
  

   the 
  needs 
  of 
  such 
  small 
  fore 
  limbs. 
  Further, 
  in 
  Stenopelix 
  Myr. 
  and 
  Compsognathus, 
  

   where 
  similar 
  elements 
  exist 
  in 
  the 
  position 
  of 
  pubes 
  and 
  ischia, 
  no 
  clavicles 
  have 
  been 
  

   preserved 
  to 
  us. 
  

  

  The 
  more 
  or 
  less 
  normal 
  position 
  in 
  which 
  these 
  bones 
  were 
  found 
  in 
  the 
  Maidstone 
  

   specimen 
  of 
  the 
  Iguanodon, 
  as 
  given 
  in 
  the 
  figure 
  accompanying 
  Prof. 
  Owen's 
  monograph, 
  

   has 
  been 
  already 
  alluded 
  to 
  ; 
  the 
  ilia 
  were 
  lying 
  parallel 
  with 
  each 
  other, 
  their 
  extremities 
  

   similarly 
  directed. 
  The 
  ischiadic 
  bones 
  lay 
  across 
  the 
  ilia 
  in 
  their 
  axes, 
  the 
  anterior 
  dilated 
  

   extremities 
  lying 
  not 
  far 
  from 
  the 
  position 
  of 
  the 
  lost 
  pubes, 
  the 
  posterior 
  directed 
  far 
  be- 
  

   hind 
  the 
  iliac 
  crests, 
  parallel 
  to 
  their 
  axes. 
  The 
  similarity 
  of 
  position 
  in 
  both, 
  and 
  the 
  

   preservation 
  of 
  relation 
  between 
  many 
  of 
  the 
  other 
  bones, 
  renders 
  it 
  probable 
  that 
  their 
  

   identification 
  with 
  ischia 
  also 
  indicates 
  their 
  natural 
  relation. 
  

  

  The 
  direction 
  of 
  the 
  ischia 
  is 
  a 
  difficult 
  point 
  to 
  determine, 
  but 
  may 
  be 
  best 
  understood 
  

   by 
  reference 
  to 
  those 
  of 
  Megadactylus 
  and 
  Clepsysaurus. 
  In 
  Hadrosaurus 
  (see 
  Lcidy's 
  

   plate 
  in 
  Cret. 
  Rept. 
  U. 
  S.) 
  this 
  bone 
  consists 
  of 
  a 
  long 
  slender 
  subcylindric 
  shaft 
  with 
  

   dilated 
  extremity. 
  The 
  dilated 
  portion 
  thin, 
  a 
  part 
  in 
  line 
  with 
  the 
  shaft 
  and 
  truncate, 
  and 
  

  

  