﻿86 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  ZDI3SrOSA.T_X:R,I.A.. 
  

  

  The 
  ilium 
  extended 
  horizontally 
  forwards, 
  and 
  supporting 
  a 
  number 
  of 
  vertebrae 
  

   anterior 
  to 
  the 
  two 
  sacrals 
  of 
  other 
  Reptilia. 
  Acetabulum 
  perforate, 
  and 
  partly 
  en- 
  

   closed 
  peripherally 
  by 
  the 
  ilium 
  and 
  pubis. 
  Pubes 
  elongate, 
  parallel 
  ; 
  ischia 
  longitudinal, 
  

   in 
  plane 
  of 
  ilium, 
  elongate, 
  with 
  distinct 
  head 
  for 
  pubis. 
  Femur 
  with 
  transverse 
  neck 
  and 
  

   head, 
  and 
  third 
  trochanter. 
  " 
  Cervical 
  and 
  anterior 
  dorsal 
  vertebra? 
  with 
  par 
  and 
  diapo- 
  

   physes, 
  for 
  articulation 
  with 
  bifurcate 
  ribs." 
  Neural 
  arches 
  of 
  dorsal 
  vertebrae 
  attached 
  

   by 
  suture 
  ; 
  of 
  sacrals, 
  shifted 
  over 
  the 
  intervertebral 
  sutures. 
  

  

  The 
  structures 
  presented 
  by 
  the 
  Dinosauria 
  have 
  presented 
  greater 
  difficulty 
  of 
  expla- 
  

   nation 
  than 
  any 
  other 
  type 
  of 
  extinct 
  vertebrates.* 
  This 
  has 
  in 
  part 
  resulted 
  from 
  the 
  

   attempt 
  so 
  assign 
  them 
  to 
  types 
  already 
  known, 
  and 
  to 
  explain 
  their 
  structures 
  in 
  accord- 
  

   ance 
  therewith 
  ; 
  a 
  course 
  scarcely 
  consistent 
  with 
  our 
  present 
  knowledge 
  of 
  the 
  peculiari- 
  

   ties 
  of 
  the 
  parts 
  themselves. 
  The 
  type 
  is 
  a 
  good 
  illustration 
  of 
  the 
  necessity 
  of 
  

   interpreting 
  extinct 
  forms 
  by 
  a 
  combination 
  of 
  the 
  " 
  law 
  of 
  successional 
  relation," 
  Avith 
  

   " 
  the 
  law 
  of 
  types 
  " 
  or 
  of 
  morphological 
  " 
  correllation," 
  and 
  not 
  by 
  either 
  alone. 
  

  

  The 
  direction 
  assigned 
  to 
  pubes 
  in 
  this 
  order, 
  is 
  suggested 
  by 
  considerations 
  explained 
  

   below. 
  They 
  have 
  probably 
  diverged 
  forwards 
  and 
  downwards 
  from 
  the 
  vertebral 
  column 
  

   and 
  their 
  great 
  length 
  indicates 
  a 
  prominent 
  abdomen. 
  The 
  only 
  Dinosaurs 
  where 
  they 
  

   are 
  preserved 
  in 
  place, 
  the 
  Stenopelix 
  valdensis 
  of 
  Von 
  Meyer, 
  and 
  Compsognathus 
  

   longipes 
  of 
  Wagner, 
  justify 
  this 
  proposition. 
  The 
  ischium 
  in 
  Stenopelix 
  and 
  Teratosaurus 
  

   is 
  a 
  broad 
  flattened 
  bone 
  slightly 
  curved 
  in 
  the 
  lateral 
  direction, 
  and 
  of 
  sufficient 
  strength 
  

   with 
  its 
  fellow, 
  to 
  support 
  the 
  weight 
  of 
  the 
  animal 
  when 
  in 
  a 
  sitting 
  posture. 
  The 
  

   pubes 
  in 
  Hadrosaurus 
  and 
  Compsognathus 
  are 
  much 
  more 
  slender 
  and 
  proximally 
  dilated 
  ; 
  

   as 
  in 
  the 
  Crocodiles 
  the 
  chief 
  support 
  of 
  each 
  is 
  derived 
  from 
  the 
  articulation 
  with 
  an 
  

   anterior 
  tuberosity 
  of 
  the 
  ischium. 
  The 
  articulation 
  with 
  the 
  ischium 
  is 
  probably 
  wanting 
  

   or 
  very 
  slight 
  and 
  ligamentous, 
  and 
  the 
  acetabulum 
  was 
  thus 
  open, 
  a 
  large 
  foramen 
  being 
  

   included 
  by 
  the 
  three 
  bones 
  which 
  usually 
  compose 
  it. 
  

  

  The 
  head 
  of 
  the 
  femur 
  is 
  transverse 
  to 
  the 
  direction 
  of 
  motion 
  of 
  the 
  condyles, 
  and 
  

   not 
  oblique 
  as 
  in 
  modern 
  lizards. 
  Hence 
  the 
  motion 
  of 
  this 
  element 
  was 
  in 
  a 
  line 
  paral- 
  

   lel 
  with 
  the 
  axis 
  of 
  the 
  body, 
  and 
  the 
  limb 
  could 
  not 
  be 
  directed 
  obliquely 
  from 
  that 
  axis 
  

   so 
  as 
  to 
  allow 
  the 
  body 
  to 
  rest 
  on 
  the 
  ground 
  between 
  them 
  in 
  the 
  ordinary 
  progression 
  of 
  

   the 
  animal, 
  as 
  is 
  the 
  case 
  with 
  Iguanas, 
  Crocodiles, 
  etc. 
  

  

  The 
  fore 
  limbs 
  appear 
  to 
  have 
  been 
  weak, 
  even 
  when 
  somewhat 
  elongate, 
  as 
  in 
  

   Iguanodon. 
  Their 
  articulation 
  with 
  the 
  scapula 
  is 
  a 
  singular 
  part 
  of 
  the 
  structure. 
  In 
  

  

  * 
  For 
  discussions 
  of 
  these 
  relations 
  see 
  Proceed. 
  Ac, 
  Nat. 
  Sci., 
  Phila., 
  1866, 
  317, 
  and 
  Proceed. 
  Amer. 
  Pliilos. 
  

   Soc, 
  I860, 
  10. 
  

  

  