﻿Systematic 
  Position 
  of 
  Meiolania 
  ; 
  Owen. 
  55 
  

  

  bearing 
  any 
  affinity 
  to 
  the 
  Chelydridse 
  or 
  Platysternidaj, 
  the 
  

   extinct 
  Chelonian 
  belongs, 
  like 
  the 
  recent 
  forms 
  of 
  the 
  Aus- 
  

   tralian 
  region, 
  to 
  the 
  group 
  Pleurodira. 
  

  

  I 
  am 
  indebted 
  to 
  Dr. 
  H. 
  Woodward 
  for 
  permission 
  to 
  

   examine 
  the 
  material 
  of 
  Meiolania 
  in 
  the 
  British 
  Museum. 
  

  

  There 
  can 
  be 
  no 
  doubt 
  whatever 
  that 
  Meiolania 
  is 
  a 
  Che- 
  

   lonian 
  ; 
  and 
  the 
  only 
  question 
  is, 
  does 
  it 
  belong 
  to 
  the 
  

   Cryptodira 
  (the 
  opinion 
  held 
  by 
  Prof. 
  Huxley) 
  or 
  to 
  the 
  

   Pleurodira 
  (the 
  view 
  of 
  Mr. 
  Boulenger) 
  ? 
  

  

  Mr. 
  Boulenger's 
  reasons 
  for 
  the 
  Pleurodiran 
  nature 
  of 
  

   Meiolania 
  are 
  the 
  following 
  : 
  — 
  

  

  " 
  1. 
  The 
  pterygoids 
  are 
  very 
  broad, 
  not 
  narrowed 
  poste- 
  

   riorly 
  ; 
  their 
  outer 
  palatal 
  borders, 
  instead 
  of 
  being 
  emar- 
  

   ginate, 
  form 
  wing-like 
  expansions. 
  

  

  " 
  2. 
  The 
  tympanic 
  cavity 
  is 
  completely 
  surrounded 
  by 
  the 
  

   bony 
  ' 
  roof,' 
  whilst 
  in 
  all 
  known 
  Cryptodira, 
  however 
  great 
  

   the 
  development 
  of 
  the 
  roof, 
  the 
  tympanic 
  disk 
  is 
  free 
  behind. 
  

  

  " 
  3. 
  The 
  mandible 
  articulates 
  with 
  the 
  skull 
  by 
  a 
  condyle 
  

   fitting 
  into 
  an 
  articular 
  concavity 
  of 
  the 
  quadrate 
  — 
  a 
  charac- 
  

   ter 
  by 
  which 
  the 
  Pleurodiran 
  Chelonians 
  differ 
  from 
  all 
  other 
  

   Reptilia, 
  so 
  far 
  as 
  I 
  am 
  aware. 
  

  

  " 
  4. 
  The 
  cervical 
  vertebras 
  are 
  those 
  of 
  a 
  Pleurodiran 
  ; 
  a 
  

   strong 
  and 
  long 
  transverse 
  process 
  is 
  present, 
  and 
  the 
  poste- 
  

   rior 
  borders 
  of 
  the 
  odontoid 
  bone 
  and 
  of 
  the 
  second 
  centrum 
  

   are 
  deeply 
  emarginate 
  interiorly, 
  terminating 
  in 
  two 
  diverging 
  

   processes 
  exactly 
  as 
  in 
  Ghelys." 
  

  

  Now 
  let 
  us 
  consider 
  the 
  principal 
  characters 
  of 
  the 
  

   skull 
  of 
  the 
  Pleurodira, 
  and 
  see 
  how 
  far 
  we 
  find 
  these 
  in 
  

   Meiolania. 
  

  

  The 
  principal 
  characters 
  in 
  the 
  skull 
  in 
  the 
  living 
  Pleuro- 
  

   dira 
  are 
  : 
  — 
  

  

  1. 
  The 
  quadrate 
  is 
  connected 
  with 
  the 
  basisphenoid, 
  some- 
  

   times 
  witli 
  the 
  basioccipital 
  also 
  (Podocnemididaj) 
  ; 
  in 
  all 
  the 
  

   Cryptodira 
  and 
  the 
  Trionychoidea 
  the 
  pterygoids 
  extend 
  

   between 
  these 
  elements. 
  

  

  2. 
  The 
  prefrontals 
  are 
  without 
  descending 
  processes 
  joining 
  

   the 
  vomer 
  (Cope). 
  

  

  3. 
  The 
  pterygoids 
  are 
  turned 
  up 
  at 
  the 
  anterior 
  outer 
  ends. 
  

  

  4. 
  The 
  front 
  of 
  the 
  brain-case, 
  between 
  quadrate 
  and 
  pet- 
  

   rosal 
  (prootic), 
  is 
  not 
  produced, 
  but 
  smooth. 
  (The 
  only 
  

   exception 
  among 
  the 
  Cryptodira, 
  which 
  all 
  show 
  this 
  produc- 
  

   tion, 
  is 
  found 
  in 
  Dermochelys.) 
  

  

  5. 
  There 
  is 
  no 
  free 
  epipterygoid 
  (columella) 
  . 
  

  

  6. 
  The 
  tympanic 
  cavity 
  is 
  more 
  or 
  less 
  surrounded 
  by 
  the 
  

   extension 
  of 
  the 
  quadrate. 
  

  

  