﻿AND 
  AYES 
  OF 
  NORTH 
  AMERICA. 
  27 
  

  

  Opisthotic 
  united 
  with 
  exoccipital 
  ; 
  brain 
  case 
  not 
  closed 
  before 
  prootics 
  ; 
  palatines 
  

   united 
  all 
  round 
  ; 
  sacrum 
  of 
  two 
  or 
  one 
  vertebra 
  ; 
  pubes 
  transverse. 
  

  

  LACERTILIA. 
  

  

  Opisthotic 
  distinct 
  and 
  distally 
  free 
  from 
  the 
  cranium 
  ; 
  brain 
  case 
  partly 
  closed 
  before 
  

   prootic, 
  palatines 
  united. 
  

  

  PYTHONOMORPHA. 
  

  

  Opisthotic 
  distinct, 
  free 
  from 
  cranium 
  except 
  proximally 
  ; 
  brain 
  case 
  nearly 
  closed 
  

   anteriorly, 
  palatines 
  attached 
  behind 
  only. 
  

  

  OPHIDIA. 
  

   ICHTHYOPTERYGIA. 
  

  

  Elements 
  of 
  the 
  limbs 
  beyond 
  the 
  humerus 
  not 
  differentiated, 
  in 
  indefinite 
  number. 
  

  

  Postorbital 
  and 
  supertympanic 
  bones 
  over 
  the 
  temporal 
  fossa. 
  

  

  Quadratum 
  solidly 
  united 
  by 
  suture 
  with 
  the 
  prootic 
  opisthotic 
  and 
  quadratojugal. 
  

  

  Sacrum 
  none. 
  

  

  Pubes 
  and 
  ischia 
  transverse 
  and 
  in 
  contact. 
  Neural 
  arches 
  free. 
  

  

  Premaxillary 
  divided. 
  

  

  ARCHOSAURIA. 
  

  

  Elements 
  of 
  the 
  limbs, 
  of 
  the 
  pes 
  and 
  manus 
  differentiated, 
  in 
  definite 
  number. 
  

  

  " 
  Postorbitals 
  and 
  supratemporals 
  " 
  of 
  Owen 
  wanting. 
  

  

  Quadratum 
  immoveably 
  united 
  by 
  suture 
  with 
  opisthotic, 
  prootic 
  and 
  quadratojugal. 
  

  

  Sacrum 
  of 
  from 
  one 
  to 
  six 
  vertebrae. 
  

  

  Neural 
  arches 
  attached 
  by 
  suture 
  in 
  most. 
  

  

  Premaxillary 
  divided. 
  

  

  Cranial 
  walls 
  cartilaginous 
  anteriorly. 
  

  

  Palatine 
  boners 
  in 
  contact 
  with 
  maxilliaries, 
  and 
  united 
  by 
  suture 
  with 
  them. 
  

  

  Circulatory 
  System 
  (known 
  only 
  in 
  the 
  Crocodilia). 
  Heart 
  with 
  complete 
  septum 
  of 
  the 
  

  

  ventricles 
  ; 
  a 
  communication 
  between 
  aorta 
  roots. 
  

   Nervous 
  System 
  (known 
  only 
  in 
  the 
  Crocodilia). 
  Cerebellum 
  with 
  small 
  lateral 
  lobes 
  and 
  

  

  weak 
  plicae. 
  

  

  TESTUDINATA. 
  

  

  Parts 
  of 
  limbs 
  differentiated. 
  

  

  Dorsal 
  vertebras 
  without 
  mobility 
  : 
  no 
  clavicle, 
  a 
  procoracoid 
  continuous 
  with 
  scapula 
  : 
  

  

  ilium 
  vertical, 
  acetabulum 
  complete. 
  

   Sternum 
  not 
  in 
  connection 
  with 
  coracoid, 
  composed 
  at 
  least 
  of 
  eight 
  or 
  more 
  bilateral 
  

  

  elements, 
  and 
  extending 
  posteriorly 
  to 
  beneath 
  the 
  pelvis. 
  

  

  