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  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  Teeth 
  none. 
  

  

  Quadratum 
  immoveably 
  fixed 
  by 
  articulation 
  with 
  the 
  large 
  pro 
  and 
  opisthotics. 
  

  

  Cranial 
  cavity 
  not 
  ossified 
  anteriorly; 
  no 
  ali 
  or 
  orbitosphenoid. 
  

  

  Palatine 
  bones 
  attached 
  anteriorly. 
  

  

  No 
  postorbital 
  or 
  supratemporal 
  elements. 
  

  

  Two 
  sacral 
  vertebrae 
  : 
  ischia 
  and 
  pubes 
  more 
  or 
  less 
  transverse, 
  the 
  latter 
  sometimes 
  not 
  

  

  in 
  contact. 
  

   Costal 
  and 
  vertebral 
  elements 
  usually 
  united 
  into 
  a 
  dorsal 
  shield 
  : 
  dorsal 
  corium 
  ossified. 
  

   Circulatory 
  and 
  Nervous 
  Systems, 
  much 
  as 
  in 
  Lacertilia. 
  

  

  PTEROSAURIA. 
  

  

  Limbs 
  differentiated, 
  one 
  digit 
  excessively 
  elongated 
  for 
  aerial 
  progression. 
  

  

  Postorbital 
  and 
  supratempoial 
  roof 
  wanting. 
  

  

  Sacrum 
  of 
  from 
  three 
  to 
  five 
  vertebra?. 
  

  

  Inferior 
  pelvic 
  elements 
  distinct, 
  the 
  pubes 
  set 
  parallel, 
  directed 
  forwards 
  and 
  not 
  joined. 
  

  

  Neural 
  arches 
  consolidated. 
  

  

  Palatine 
  elements 
  united 
  ; 
  one 
  premaxillary. 
  

  

  LACERTILIA. 
  

  

  The 
  distal 
  parts 
  of 
  limbs 
  differentiated 
  ; 
  no 
  supratemporal 
  or 
  postorbital 
  bones. 
  

   Quadratum 
  not 
  in 
  contact 
  with 
  prootic, 
  articulating 
  freely 
  with 
  opisthotic 
  ; 
  no 
  quadrato- 
  

  

  jugal. 
  

   Opisthotic 
  sessile 
  not 
  distinct. 
  

   Sternum 
  composed 
  of 
  but 
  two 
  elements, 
  which 
  are 
  continuous 
  with 
  remainder 
  of 
  scapular 
  

  

  arch. 
  

   Cranial 
  cavity 
  not 
  ossified 
  anteriorly 
  to 
  prootic. 
  

   Palatine 
  bones 
  solidly 
  attached 
  to 
  maxilla?; 
  a 
  symphysis 
  mandibuli. 
  

   Squamosal 
  usually 
  present; 
  premaxillary 
  usually 
  single. 
  

   Limbs 
  ambulatory, 
  when 
  present. 
  

  

  Sacrum 
  of 
  two 
  vertebra?, 
  when 
  present 
  ; 
  ribs 
  single 
  headed. 
  

   Neural 
  arches 
  not 
  united 
  by 
  suture, 
  chevron 
  bones 
  present. 
  

   Pubes 
  and 
  ischia 
  transverse, 
  united 
  in 
  pairs. 
  

   Circulatory 
  System. 
  Heart 
  with 
  imperfect 
  septum 
  atriorum, 
  no 
  communication 
  between 
  

  

  aorta 
  roots. 
  

   Nervous 
  System. 
  Cerebellum 
  without 
  lateral 
  lobes 
  or 
  plicae. 
  

  

  