﻿Wieland 
  — 
  Evolution 
  of 
  the 
  Testudinate 
  Humerus. 
  415 
  

  

  the 
  first 
  step 
  towards 
  an 
  ungulate 
  type 
  of 
  foot. 
  As 
  seen 
  in 
  

   the 
  accompanying 
  figs. 
  1-4, 
  the 
  present 
  is 
  a 
  plastic 
  type 
  of 
  

   humerus 
  which 
  may 
  be 
  well 
  marked 
  in 
  the 
  case 
  of 
  forms 
  only 
  

   specifically 
  distinct. 
  The 
  humerus 
  of 
  the 
  senile 
  genus 
  Mio- 
  

   lania 
  Owen 
  (15, 
  22) 
  would 
  probably 
  fall 
  within 
  the 
  parachelic 
  

   series. 
  Testudo 
  polyjphemus 
  — 
  with 
  a 
  complex 
  as 
  opposed 
  to 
  a 
  

   simple 
  carpus, 
  and 
  an 
  innominate 
  pelvis 
  — 
  affords 
  a 
  good 
  

   example 
  of 
  the 
  distal 
  grooving 
  and 
  other 
  modifications 
  here 
  

   emphasized. 
  

  

  Parachelic 
  humeri 
  of 
  Galapagos 
  Islands 
  tortoises. 
  Outlined 
  from 
  Giinther 
  (9),* 
  

   Figures 
  1 
  and 
  4. 
  — 
  Testudo 
  elephantopus 
  Harlan, 
  — 
  ventral 
  and 
  dorsal 
  view. 
  

   Figures 
  2 
  and 
  3. 
  — 
  Testudo 
  ephippium 
  Giinther, 
  f 
  — 
  ventral 
  and 
  dorsal 
  view. 
  

  

  j 
  a, 
  bead: 
  b, 
  radial 
  crest; 
  c, 
  ulnar 
  crest; 
  d, 
  ectepicondyle 
  ; 
  e, 
  ectepi- 
  

   l 
  condylar 
  foramen 
  (or 
  groove); 
  /, 
  ectocondyle; 
  g, 
  entocondyle. 
  

  

  The 
  Chelic 
  humerus. 
  — 
  The 
  fundamental 
  difference 
  between 
  

   the 
  second 
  or 
  chelic 
  type 
  of 
  humerus 
  and 
  the 
  preceding 
  con- 
  

   sists 
  in 
  the 
  straightening 
  of 
  the 
  distal 
  extremity 
  into 
  a 
  simple 
  

   rounded 
  end 
  bearing 
  the 
  articular 
  cartilage, 
  without 
  develop- 
  

   ment 
  into 
  a 
  grooved 
  articular 
  surface. 
  The 
  ulnar 
  crest 
  maybe 
  

   more 
  prominent, 
  and 
  the 
  ectepicondylar 
  foramen 
  oftener 
  seen 
  

   as 
  a 
  groove 
  more 
  distal 
  in 
  position, 
  but 
  always 
  near 
  the 
  outer 
  

   edge. 
  

  

  Most 
  distinctly 
  clawed 
  Testudinates 
  have 
  this 
  form 
  of 
  

   humerus, 
  and 
  as 
  these 
  range 
  from 
  land 
  and 
  freshwater 
  to 
  web- 
  

   toed 
  and 
  partly 
  brackish 
  water 
  species, 
  distinct 
  variations, 
  such 
  

   as 
  increase 
  or 
  decrease 
  in 
  the 
  angle 
  between 
  and 
  size 
  of 
  the 
  

   ulnar 
  and 
  radial 
  crests, 
  may 
  be 
  expected, 
  and 
  are 
  present. 
  

  

  * 
  Nob. 
  in 
  parentheses 
  refer 
  to 
  list 
  of 
  references 
  page 
  423. 
  

  

  f 
  Dr. 
  Baur 
  has 
  proposed 
  to 
  call 
  this 
  tortoise 
  Testudo 
  Abingdonii 
  (3), 
  but 
  Roths- 
  

   child 
  (16) 
  and 
  Giinther 
  (11) 
  have 
  shown 
  that 
  T. 
  ephippium 
  is 
  to 
  be 
  retained. 
  

  

  