﻿Systematic 
  Position 
  q/" 
  Meiolania, 
  Owen. 
  59 
  

  

  Opisthocoelian 
  vertebrce 
  are 
  present 
  in 
  those 
  Ckelonians 
  

   which 
  have 
  long 
  free 
  tails. 
  

  

  There 
  are 
  Testudinata 
  with 
  nearly 
  as 
  many 
  caudal 
  verte- 
  

   bras 
  as 
  Chelydra 
  and 
  the 
  others, 
  but 
  in 
  all 
  these 
  the 
  tail 
  is 
  

   not 
  free, 
  but 
  covered 
  for 
  the 
  greater 
  part 
  by 
  the 
  carapace, 
  and 
  

   we 
  never 
  find 
  opisthocoelian 
  vertebras. 
  

  

  Together 
  with 
  the 
  opisthocoelian 
  vertebras 
  we 
  always 
  find 
  

   well-developed 
  intercentra 
  (chevron 
  bones). 
  They 
  may 
  be 
  

   present 
  in 
  rudimentary 
  condition 
  in 
  long 
  tails 
  without 
  opis- 
  

   thocoelian 
  vertebras, 
  as 
  in 
  Emys 
  europcea 
  and 
  Blandingii, 
  in 
  

   Chelymys 
  victories 
  at 
  the 
  posterior 
  end 
  of 
  the 
  tail, 
  and 
  in 
  

   others. 
  In 
  Toxochelys, 
  Cope, 
  they 
  are 
  even 
  well 
  developed. 
  

  

  It 
  was 
  especially 
  the 
  caudal 
  vertebras 
  of 
  Meiolania 
  which 
  

   led 
  Prof. 
  Huxley 
  to 
  the 
  conclusion 
  of 
  its 
  affinity 
  with 
  the 
  

   Chelydridas 
  ; 
  but 
  I 
  think 
  that 
  this 
  character 
  is 
  not 
  conclusive. 
  

   I 
  imagine 
  that 
  opisthocoelian 
  caudal 
  vertebras 
  could 
  be 
  deve- 
  

   loped 
  in 
  any 
  group 
  of 
  the 
  Chelonians. 
  These 
  characters 
  are 
  

   adaptive 
  and 
  cannot 
  be 
  used 
  for 
  the 
  genetic 
  relations 
  of 
  

   groups. 
  

  

  But 
  how 
  can 
  we 
  determine 
  the 
  systematic 
  position 
  of 
  

   Meiolania 
  among 
  the 
  Cryptodira 
  ? 
  

  

  That 
  Meiolania 
  is 
  a 
  terrestrial 
  herbivorous 
  Cryptodiran 
  

   there 
  is 
  no 
  doubt. 
  The 
  only 
  true 
  terrestrial 
  herbivorous 
  

   Cryptodira 
  we 
  know 
  are 
  the 
  Testudinidas 
  ; 
  some 
  more 
  or 
  less 
  

   terrestrial 
  forms 
  we 
  find 
  also 
  among 
  the 
  Emydidas. 
  

  

  We 
  know 
  that 
  the 
  true 
  Testudinidas 
  originated 
  from 
  Emy- 
  

   didas. 
  Why 
  is 
  not 
  Meiolania 
  also 
  a 
  true 
  Testudinid 
  ? 
  Or 
  

   did 
  it 
  take 
  its 
  origin 
  from 
  one 
  of 
  the 
  other 
  families 
  of 
  the 
  

   Cryptodira, 
  the 
  Chelydridas, 
  or 
  Staurotypidas, 
  the 
  Cinoster- 
  

   nidas, 
  or 
  another 
  family 
  ? 
  

  

  I 
  am 
  inclined 
  to 
  consider 
  Meiolania 
  as 
  a 
  highly 
  specialized 
  

   branch 
  of 
  the 
  true 
  land-tortoises, 
  the 
  Testudinidce, 
  the 
  true 
  

   Testudinid 
  characters 
  of 
  which 
  are 
  only 
  obscured 
  by 
  the 
  enor- 
  

   mous 
  development 
  of 
  dermal 
  ossifications, 
  especially 
  on 
  the 
  

   skull, 
  which 
  gave 
  to 
  it 
  quite 
  an 
  extraordinary 
  appearance. 
  

  

  My 
  reasons 
  are 
  the 
  following 
  : 
  — 
  

  

  The 
  lower 
  face 
  of 
  the 
  skull 
  resembles 
  most 
  the 
  Testudinidas 
  

   among 
  the 
  Cryptodira. 
  

  

  The 
  long 
  vomer 
  has 
  the 
  strong 
  characteristic 
  keel. 
  The 
  

   situation 
  and 
  form 
  of 
  the 
  foramina 
  palatina 
  are 
  just 
  as 
  in 
  this 
  

   family, 
  and 
  so 
  are 
  the 
  pterygoids. 
  

  

  either 
  to 
  the 
  Staurotvpidse 
  or 
  to 
  the 
  Cinosternidse. 
  There 
  are 
  only 
  ten 
  

   peripheralia 
  (marginal 
  bones), 
  and 
  the 
  dermal 
  plates 
  are 
  not 
  entirely 
  

   absent. 
  

  

  