﻿334 
  

  

  BABCOCK: 
  NEW 
  ENGLAND 
  TURTLES. 
  

  

  The 
  weight 
  of 
  the 
  specimen 
  from 
  No 
  Man's 
  Land 
  in 
  the 
  Museum 
  of 
  the 
  Boston 
  Society 
  of 
  

   Natural 
  History 
  was 
  about 
  600 
  pounds. 
  

  

  Color: 
  — 
  Dark 
  brown, 
  greenish, 
  or 
  blackish, 
  sometimes 
  uniform, 
  sometimes 
  spotted 
  with 
  

   yellow. 
  

  

  Description. 
  — 
  The 
  vertebrae 
  and 
  ribs 
  are 
  not 
  fused 
  with 
  the 
  carapace. 
  There 
  are 
  no 
  

   epidermal 
  shields, 
  but 
  the 
  body 
  is 
  covered 
  ^^^th 
  a 
  thick, 
  smooth, 
  leathery 
  skin. 
  The 
  limbs 
  

   are 
  transformed 
  into 
  paddles. 
  The 
  neck 
  is 
  not 
  retractile. 
  The 
  shell 
  has 
  twelve 
  longitudinal 
  

   ridges, 
  seven 
  above 
  and 
  five 
  beneath. 
  

  

  The 
  chief 
  pecuUarity 
  of 
  this 
  turtle 
  consists 
  in 
  the 
  structure 
  of 
  the 
  shell 
  and 
  arrangement 
  

   of 
  the 
  plates. 
  The 
  dorsal 
  and 
  ventral 
  halves 
  are 
  continuous, 
  forming 
  one 
  unbroken 
  case. 
  

   This 
  is 
  composed 
  of 
  many 
  irregular 
  bony 
  plates, 
  fitting 
  closely 
  together 
  and 
  giving 
  the 
  shell 
  a 
  

   "beautiful 
  mosaic 
  appearance." 
  The 
  converging 
  longitudinal 
  ridges 
  are 
  formed 
  by 
  lateral 
  

   rows 
  of 
  larger 
  plates, 
  forming 
  angles 
  in 
  the 
  bony 
  shell. 
  There 
  is 
  no 
  contact 
  between 
  the 
  shell 
  

   and 
  the 
  internal 
  skeleton 
  except 
  in 
  an 
  articulation 
  between 
  the 
  nuchal 
  bone 
  and 
  the 
  eighth 
  

   cervdcal 
  vertebra. 
  Between 
  the 
  epidermis 
  and 
  the 
  shell 
  there 
  is 
  a 
  one-inch 
  layer 
  of 
  fatty 
  tissue. 
  

   The 
  tail 
  is 
  short, 
  although 
  containing 
  about 
  twenty 
  vertebrae. 
  The 
  front 
  flippers 
  are 
  very 
  

   long 
  and 
  large. 
  None 
  of 
  the 
  fingers 
  projects 
  free, 
  hence 
  none 
  has 
  a 
  nail. 
  In 
  another 
  impor- 
  

   tant 
  respect 
  the 
  Leatherback 
  and 
  its 
  few 
  fossil 
  relatives 
  differ 
  from 
  all 
  other 
  turtles. 
  This 
  is 
  

   in 
  the 
  fact 
  that 
  the 
  parietal 
  bone 
  does 
  not 
  send 
  a 
  plate 
  downward 
  in 
  front 
  of 
  the 
  exit 
  of 
  the 
  tri- 
  

   geminal 
  nerve 
  to 
  join 
  the 
  pterygoid 
  (Hay). 
  For 
  a 
  very 
  detailed 
  work 
  on 
  the 
  skull 
  characters, 
  

   see 
  Das 
  Kopfskelet 
  von 
  Dermochelys 
  coriacea 
  L., 
  by 
  Ludwig 
  Nick 
  (1912). 
  

  

  Origin 
  and 
  Development. 
  — 
  The 
  position 
  of 
  this 
  species 
  in 
  the 
  evolutionary 
  system 
  has 
  

   been 
  a 
  much 
  debated 
  subject. 
  One 
  group 
  of 
  naturalists 
  considers 
  it 
  the 
  sole 
  remnant 
  of 
  a 
  

   primitive 
  group, 
  while 
  another 
  looks 
  upon 
  it 
  as 
  a 
  most 
  highly 
  specialized 
  descendant 
  of 
  the 
  

   Chelonidae. 
  

  

  Tekro-Aquatic 
  

  

  Ancestral 
  chelonians 
  with 
  solid 
  cara- 
  

   pace 
  and 
  plastron 
  

  

  h 
  

  

  Aquatic, 
  Flitviatile 
  

  

  ( 
  Primary 
  littoral 
  stage 
  with 
  unim- 
  [ 
  

   Aquatic, 
  Littoral 
  ■— 
  >2 
  i 
  . 
  , 
  j 
  i 
  . 
  i 
  — 
  i 
  

  

  ( 
  paired 
  carapace 
  and 
  plastron 
  ) 
  . 
  

  

  Aquatic, 
  Pelagic 
  

  

  r 
  Primary 
  pelagic 
  stage 
  with 
  cara- 
  | 
  

   — 
  ■>3 
  <. 
  pace 
  and 
  plastron 
  progressively 
  /- 
  

   ( 
  atrophied 
  j 
  

  

  Secondary 
  littoral 
  stage, 
  primary 
  

   carapace 
  and 
  plastron 
  reduced; 
  a 
  

   secondary 
  carapace 
  and 
  plastron 
  

   of 
  dermal 
  ossicles 
  

  

  {Secondary 
  pelagic 
  stage, 
  second- 
  

   ary 
  carapace 
  retrogressive, 
  sec- 
  

   ondary 
  plastron 
  reduced 
  

  

  