﻿E. 
  C. 
  Case 
  — 
  Stylemys 
  nebracensis. 
  135 
  

  

  Aet. 
  XXX. 
  — 
  Notes 
  on 
  a 
  specimen 
  of 
  Stylemys 
  nebra- 
  

   censis 
  Leidy; 
  by 
  E. 
  C. 
  Case. 
  

  

  The 
  University 
  of 
  Michigan 
  expedition 
  to 
  the 
  Big 
  Bad 
  

   Lands 
  of 
  South 
  Dakota, 
  in 
  1917, 
  recovered 
  the 
  shell 
  of 
  a 
  

   large 
  specimen 
  of 
  Stylemys 
  nebracensis 
  in 
  such 
  a 
  good 
  

   state 
  of 
  preservation 
  that 
  it 
  was 
  determined 
  to 
  remove 
  

   the 
  bone 
  from 
  the 
  matrix 
  and 
  mount 
  the 
  shell 
  as 
  a 
  recent 
  

   specimen 
  would 
  be 
  mounted. 
  In 
  removing 
  the 
  shell 
  the 
  

   pelvic 
  and 
  pectoral 
  girdles, 
  one 
  humerus 
  and 
  five 
  poste- 
  

   rior 
  cervical 
  vertebrae 
  were 
  found. 
  The 
  preparation 
  and 
  

   mounting 
  of 
  the 
  parts 
  has 
  added 
  several 
  points 
  to 
  our 
  

   knowledge 
  of 
  the 
  anatomy 
  of 
  this 
  long 
  known 
  form. 
  

  

  In 
  all 
  the 
  published 
  figures 
  of 
  Stylemys 
  the 
  shell 
  has 
  

   been 
  shown 
  as 
  it 
  occurs 
  in 
  the 
  field, 
  more 
  or 
  less 
  crushed 
  

   down. 
  The 
  general 
  impression 
  has 
  been 
  that 
  the 
  form 
  

   was 
  somewhat 
  depressed 
  though 
  Hay 
  has 
  shown 
  that 
  the 
  

   height 
  varies 
  in 
  different 
  individuals 
  with 
  age. 
  This 
  

   specimen 
  mounted 
  with 
  the 
  crushing 
  corrected 
  shows 
  that 
  

   the 
  shell 
  was 
  relatively 
  high 
  with 
  nearly 
  vertical 
  sides, 
  

   quite 
  similar 
  to 
  that 
  of 
  the 
  Galapagos 
  tortoise. 
  

  

  The 
  pelvis, 
  hitherto 
  very 
  imperfectly 
  known, 
  is 
  nearly 
  

   complete. 
  It 
  is 
  typically 
  that 
  of 
  a 
  land 
  turtle, 
  resembling 
  

   most 
  closely 
  the 
  pelvis 
  of 
  Kinixys. 
  The 
  greatest 
  pecu- 
  

   liarity 
  is 
  in 
  the 
  extremely 
  heavy 
  ischial 
  region. 
  The 
  

   symphasis 
  is 
  tightly 
  closed 
  and 
  the 
  posterior 
  ends 
  of 
  the 
  

   ischia 
  are 
  very 
  rugose 
  with 
  the 
  posterior 
  end 
  broadly 
  con- 
  

   cave. 
  This 
  posterior 
  end 
  or 
  edge 
  is 
  sharply 
  down-turned 
  

   so 
  that 
  it 
  overhangs 
  the 
  lower 
  surface 
  and 
  forms 
  deep 
  

   pits 
  of 
  either 
  side. 
  The 
  whole 
  pelvis 
  evidently 
  stood 
  at 
  

   an 
  angle 
  to 
  the 
  inner 
  surface 
  of 
  the 
  plastron 
  as 
  in 
  

   Kinixys. 
  

  

  The 
  pectoral 
  girdle 
  presents 
  no 
  peculiarities. 
  

  

  The 
  free 
  vertebrae 
  include 
  the 
  first 
  dorsal 
  and 
  the 
  fiYQ 
  

   posterior 
  cervicals, 
  hitherto 
  unknown. 
  These 
  are 
  all 
  of 
  

   the 
  testudinate 
  type 
  and 
  closely 
  resemble 
  the 
  correspond- 
  

   ing 
  vertebrae 
  of 
  Gopherus 
  and 
  Kinixys. 
  The 
  anterior 
  

   dorsal 
  is 
  larger 
  than 
  the 
  others, 
  it 
  was 
  free 
  in 
  the 
  shell 
  

   with 
  a 
  strong 
  neural 
  spine 
  for 
  attachment 
  to 
  the 
  cara- 
  

   pace 
  ; 
  there 
  is 
  a 
  pair 
  of 
  small 
  anterior 
  ribs 
  attached 
  to 
  

   the 
  middle 
  of 
  the 
  centrum. 
  Similar 
  ribs 
  were 
  present 
  in 
  

   the 
  specimen 
  of 
  Kinixys 
  examined 
  but 
  not 
  in 
  the 
  speci- 
  

   men 
  of 
  Gopherus; 
  it 
  is 
  said 
  to 
  be 
  a 
  variable 
  character. 
  

  

  