﻿Dr. 
  G. 
  Baur 
  on 
  " 
  Aulacochelys," 
  Lydekker, 
  &c. 
  273 
  

  

  XXIX. 
  — 
  On 
  ft 
  Aulacochelys," 
  Lydekker, 
  and 
  the 
  Systematic 
  

   Position 
  of 
  Anosteira, 
  Leidy, 
  and 
  Pseudotrionyx, 
  Dollo. 
  

   By 
  Dr. 
  Gr. 
  Baur, 
  New 
  Haven, 
  Conn. 
  

  

  In 
  the 
  January 
  number 
  of 
  this 
  Journal 
  Mr. 
  R. 
  Lydekker 
  * 
  

   establislied 
  a 
  genus 
  Aulacochelys 
  for 
  Trionyx 
  circumsulcatus, 
  

   Owen. 
  

  

  The 
  character 
  of 
  this 
  genus 
  consists 
  in 
  the 
  " 
  presence 
  of 
  a 
  

   deep 
  groove 
  in 
  the 
  free 
  border 
  of 
  the 
  costals," 
  and 
  in 
  this 
  it 
  

   is 
  said 
  to 
  differ 
  " 
  from 
  all 
  species 
  of 
  Trionyx." 
  

  

  At 
  first 
  we 
  may 
  ask, 
  Is 
  a 
  groove 
  in 
  a 
  portion 
  of 
  a 
  dermal 
  

   ossification 
  of 
  generic 
  value 
  ? 
  and 
  may 
  safely 
  answer 
  that 
  it 
  

   is 
  not. 
  

  

  Such 
  a 
  groove 
  is 
  very 
  common 
  at 
  the 
  outer 
  end 
  of 
  the 
  

   united 
  hyo- 
  and 
  hypoplastic 
  in 
  the 
  Trionychidae 
  : 
  and 
  this 
  

   fact 
  alone 
  contradicts 
  the 
  generic 
  value 
  of 
  such 
  a 
  structure. 
  

   This 
  groove 
  may 
  be 
  present 
  or 
  absent 
  in 
  the 
  same 
  species 
  ; 
  it 
  

   is 
  generally 
  present 
  in 
  old 
  individuals. 
  But 
  if 
  we 
  find 
  it 
  

   even 
  on 
  the 
  pleuralia 
  (costals) 
  of 
  living 
  Trionychida3, 
  it 
  is 
  

   simply 
  individual 
  and 
  without 
  any 
  systematic 
  value 
  what- 
  

   ever. 
  In 
  old 
  specimens 
  of 
  Aspidonectes 
  fercx, 
  Schn., 
  and 
  

   of 
  Aspidonectes 
  muticus, 
  Les., 
  this 
  groove 
  is 
  very 
  well 
  deve- 
  

   loped. 
  In 
  other 
  specimens 
  of 
  the 
  same 
  species 
  and 
  different 
  

   Trionychidse 
  I 
  find 
  no 
  trace 
  of 
  it. 
  

  

  The 
  genus 
  Aulacochelys, 
  Lydekker, 
  therefore 
  is 
  not 
  entitled 
  

   to 
  recognition 
  as 
  being 
  based 
  upon 
  such 
  trivial 
  characters. 
  

  

  In 
  the 
  same 
  paper 
  a 
  new 
  species 
  of 
  Anosteira 
  is 
  proposed 
  

   and 
  named 
  A. 
  anglica. 
  It 
  is 
  based 
  on 
  one 
  anterior 
  marginal 
  

   and 
  a 
  xiphiplastral. 
  This 
  form 
  cannot 
  be 
  distinguished 
  from 
  

   the 
  Anosteira 
  radulata, 
  Cope 
  f, 
  described 
  in 
  1871 
  and 
  figured 
  

   in 
  Prof. 
  Cope's 
  % 
  well-known 
  work 
  on 
  the 
  Vertebrata 
  of 
  the 
  

   Tertiaries 
  of 
  the 
  West. 
  

  

  It 
  seems 
  that 
  Mr. 
  Lydekker 
  was 
  not 
  aware 
  of 
  the 
  existence 
  

   of 
  another 
  species 
  of 
  Anosteira 
  except 
  Leidy's 
  type. 
  

  

  In 
  the 
  same 
  number 
  of 
  this 
  Magazine 
  § 
  I 
  have 
  remarked 
  

   that 
  Anosteira 
  belongs 
  either 
  to 
  the 
  Staurotypidee 
  or 
  Cino- 
  

  

  * 
  Lydekker, 
  R., 
  " 
  Preliminary 
  Nutice 
  of 
  new 
  Fossil 
  Chelonia," 
  Ann. 
  

   & 
  Mag. 
  Nat. 
  Hist. 
  Jan. 
  1889, 
  p. 
  53. 
  

  

  t 
  Cope, 
  E. 
  D., 
  " 
  Descriptions 
  of 
  new 
  Extinct 
  Reptiles 
  from 
  the 
  Upper 
  

   Green 
  River 
  Eocene 
  Basin, 
  Wyoming,'' 
  Proc. 
  Am. 
  Phil. 
  Soc. 
  vol. 
  xii. 
  

   Jan. 
  1871-Dec. 
  1872 
  : 
  Philadelphia, 
  1873 
  (paper 
  published 
  Oct. 
  12, 
  1871). 
  

  

  X 
  Cope, 
  E. 
  D., 
  ' 
  The 
  Vertebrata 
  of 
  the 
  Tertiary 
  Formations 
  of 
  the 
  

   West,' 
  Book 
  I., 
  Washington, 
  1883 
  (published 
  Jan. 
  1885J, 
  p. 
  128, 
  pi. 
  xviii. 
  

   rigs. 
  18, 
  19. 
  

  

  § 
  Baur, 
  Dr. 
  C, 
  " 
  The 
  .Systematic 
  Position 
  of 
  Melolania, 
  Owen," 
  Ann. 
  

   & 
  Mag. 
  Nat. 
  Hist., 
  Jan. 
  1889, 
  pp. 
  58, 
  59. 
  

  

  