﻿306 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol.96 
  

  

  and 
  Williston/ 
  we 
  may 
  identify 
  as 
  centrale 
  1. 
  Its 
  outer 
  side 
  is 
  in 
  

   juxtaposition 
  to 
  a 
  smaller 
  pentagonal 
  bone 
  regarded 
  as 
  centrale 
  2. 
  

   These 
  two 
  centralia 
  although 
  distinct 
  elements 
  in 
  this 
  individual 
  are 
  

   often 
  found 
  fused 
  into 
  a 
  single 
  bone, 
  and 
  this 
  appears 
  to 
  have 
  happened 
  

   in 
  specimen 
  No. 
  15874. 
  Williston, 
  in 
  the 
  book 
  cited, 
  observes/' 
  Among 
  

   terrestrial 
  tortoises 
  the 
  radiale 
  has 
  disappeared 
  until 
  nothing 
  is 
  left 
  of 
  

   it 
  but 
  a 
  nodule 
  of 
  cartilage 
  united 
  with 
  the 
  first 
  centrale 
  which 
  has 
  

   usurped 
  its 
  place." 
  Hay, 
  however, 
  in 
  his 
  "Fossil 
  Turtles 
  of 
  North 
  

   America," 
  continues 
  to 
  regard 
  the 
  first 
  centrale 
  as 
  the 
  radiale. 
  

  

  The 
  fifth 
  carpale 
  (pi. 
  44, 
  fig. 
  2, 
  C5) 
  is 
  present 
  and 
  remains 
  in 
  

   articulation 
  with 
  metacarpal 
  5. 
  Carpalia 
  3 
  and 
  4 
  are 
  missing. 
  The 
  

   third 
  digit 
  lacks 
  its 
  metacarpal, 
  and 
  a 
  phalange 
  is 
  missing 
  from 
  the 
  

   fifth 
  digit; 
  otherwise 
  the 
  foot 
  is 
  complete. 
  Comparison 
  of 
  these 
  

   wrist 
  and 
  foot 
  bones 
  with 
  those 
  of 
  the 
  living 
  Galapagos 
  Testudo 
  of 
  

   comparable 
  size 
  shows 
  a 
  close 
  correspondence 
  in 
  form, 
  as 
  well 
  as 
  in 
  the 
  

   arrangement 
  of 
  the 
  individual 
  elements. 
  

  

  The 
  hind 
  foot 
  of 
  No. 
  15878 
  contributes 
  nothing 
  new 
  to 
  our 
  knowl- 
  

   edge 
  of 
  the 
  pes 
  of 
  Testudo. 
  

  

  SUMMARY 
  

  

  In 
  the 
  original 
  description 
  of 
  Testudo 
  praeextans 
  Lambe 
  called 
  

   attention 
  to 
  the 
  close 
  similarity 
  in 
  the 
  form 
  of 
  the 
  epiplastral 
  beak 
  to 
  

   that 
  of 
  T. 
  thomsoni 
  but 
  concluded 
  that 
  the 
  "much 
  greater 
  propor- 
  

   tionate 
  size 
  of 
  the 
  epiplastral 
  lip 
  and 
  differences 
  throughout 
  of 
  the 
  

   elements 
  forming 
  the 
  lobe" 
  were 
  sufficient 
  to 
  indicate 
  their 
  specific 
  

   distinctness. 
  

  

  In 
  view 
  of 
  the 
  very 
  fragmentary 
  character 
  of 
  the 
  type 
  of 
  T. 
  thomsoni, 
  

   and 
  especially 
  of 
  the 
  considerable 
  variation 
  in 
  the 
  form 
  of 
  the 
  anterior 
  

   lobe 
  as 
  shown 
  by 
  the 
  present 
  specimens, 
  it 
  would 
  now 
  appear 
  that 
  

   Lambe 
  was 
  not 
  justified 
  in 
  establishing 
  the 
  new 
  species 
  T. 
  praeextans. 
  

   On 
  plastral 
  parts 
  alone 
  I 
  should 
  unhesitatingly 
  regard 
  T. 
  praeextans 
  to 
  

   be 
  a 
  synonym 
  of 
  T. 
  thomsoni, 
  which 
  has 
  priority 
  by 
  several 
  years. 
  

   However, 
  when 
  the 
  skulls 
  are 
  compared, 
  differences 
  in 
  proportion 
  of 
  

   the 
  elements 
  forming 
  the 
  skull 
  roofs, 
  and 
  the 
  different 
  widths 
  of 
  the 
  

   channels 
  on 
  the 
  triturating 
  surfaces, 
  strongly 
  suggest 
  that 
  the 
  dis- 
  

   covery 
  of 
  more 
  complete 
  materials 
  of 
  T. 
  thomsoni 
  may 
  disclose 
  other 
  

   and 
  more 
  important 
  distinctive 
  characters. 
  For 
  the 
  present, 
  there- 
  

   fore, 
  it 
  seems 
  desirable 
  to 
  continue 
  the 
  use 
  of 
  both 
  names. 
  

  

  In 
  the 
  preliminary 
  study 
  of 
  the 
  present 
  materials 
  it 
  was 
  first 
  

   thought 
  that 
  these 
  specimens 
  could 
  not 
  be 
  specifically 
  distinguished 
  

   from 
  Testudo 
  laticunea 
  Cope 
  and 
  that 
  such 
  differences 
  as 
  existed 
  might 
  

   be 
  attributed 
  to 
  the 
  female 
  sex 
  of 
  the 
  type 
  of 
  that 
  species. 
  This 
  idea 
  

   was 
  abandoned, 
  however, 
  with 
  the 
  discovery 
  that 
  the 
  Wyoming 
  

  

  ' 
  WUliston. 
  S. 
  W., 
  The 
  osteology 
  of 
  the 
  reptiles, 
  p. 
  179, 
  1925. 
  

  

  