﻿328 
  BABCOCK: 
  NEW 
  ENGLAND 
  TURTLES. 
  

  

  representatives 
  of 
  which 
  in 
  the 
  present 
  age 
  are 
  but 
  pigmies 
  as 
  compared 
  with 
  the 
  huge 
  rep- 
  

   tilian 
  forms 
  that 
  roamed 
  the 
  earth 
  during 
  the 
  Mesozoic 
  and 
  earUer 
  Tertiary 
  periods 
  when 
  

   they 
  reached 
  their 
  greatest 
  development. 
  In 
  fact, 
  there 
  are 
  only 
  two 
  groups 
  of 
  living 
  turtles 
  

   that 
  at 
  all 
  suggest 
  this 
  wonderful 
  reptilian 
  age: 
  (1) 
  the 
  Giant 
  Land 
  Tortoises 
  of 
  the 
  Galapagos 
  

   Islands 
  (named 
  Galapagos 
  = 
  Tortoise 
  Islands 
  by 
  early 
  Spanish 
  explorers) 
  and 
  of 
  the 
  Aldabra 
  

   Islands, 
  adult 
  specimens 
  of 
  which 
  have 
  been 
  known 
  to 
  weigh 
  several 
  hundred 
  pounds; 
  and 
  

   (2) 
  the 
  Leatherback 
  or 
  Trunk 
  Turtle 
  (a 
  marine 
  species) 
  which 
  is 
  included 
  in 
  the 
  New 
  England 
  

   fauna. 
  Speaking 
  of 
  the 
  order 
  as 
  a 
  whole, 
  Williston 
  (1914, 
  p. 
  216) 
  says: 
  "No 
  order 
  of 
  reptiles 
  

   of 
  the 
  past 
  or 
  present 
  is 
  more 
  sharply 
  and 
  unequivocally 
  distinguished 
  from 
  all 
  others 
  than 
  

   the 
  Chelonia 
  or 
  Testudinata. 
  No 
  order 
  has 
  had 
  a 
  more 
  uniformly 
  continuous 
  and 
  uneventful 
  

   history. 
  None 
  now 
  in 
  existence 
  has 
  had 
  a 
  longer 
  known 
  history, 
  and 
  of 
  none 
  is 
  the 
  origin 
  

   more 
  obscure. 
  The 
  first 
  known 
  members 
  of 
  the 
  order, 
  in 
  Triassic 
  times, 
  were 
  turtles 
  in 
  all 
  

   respects, 
  as 
  well 
  or 
  nearly 
  as 
  well 
  adapted 
  for 
  their 
  pecuhar 
  mode 
  of 
  life 
  as 
  are 
  those 
  now 
  Uving, 
  

   and 
  were 
  they 
  now 
  living 
  they 
  would 
  attract 
  no 
  especial 
  attention 
  from 
  the 
  ordinary 
  observer 
  

   and 
  but 
  little 
  from 
  the 
  naturalist. 
  From 
  time 
  to 
  time 
  some 
  have 
  gone 
  after 
  better 
  things, 
  and 
  

   have 
  come 
  to 
  grief, 
  but 
  the 
  main 
  line 
  has 
  remained 
  mth 
  fewer 
  improvements, 
  fewer 
  evolu- 
  

   tional 
  changes, 
  than 
  any 
  other 
  group 
  of 
  higher 
  vertebrates." 
  

  

  Gadow 
  (1901, 
  p. 
  312) 
  describes 
  turtles 
  as 
  '.'terrestrial 
  or 
  aquatic, 
  pentadactyle 
  reptiles, 
  

   with 
  walking 
  limbs 
  or 
  with 
  paddles; 
  ribs 
  with 
  capitular 
  portions 
  only, 
  two 
  sacral 
  vertebrae, 
  

   humerus 
  with 
  entepicondylar 
  foramen, 
  pubes 
  and 
  ischia 
  forming 
  symphyses, 
  quadrate 
  bones 
  

   fixed, 
  jaws 
  without 
  teeth, 
  but 
  with 
  cutting 
  horny 
  sheaths. 
  Trunk 
  encased 
  in 
  a 
  bony 
  shell, 
  

   composed 
  of 
  numerous 
  dorsal 
  and 
  ventral 
  dermal 
  bones, 
  forming 
  a 
  carapace 
  and 
  a 
  plastron, 
  

   which 
  may 
  or 
  may 
  not 
  be 
  covered 
  with 
  horny 
  shields. 
  Copulatory 
  organ 
  unpaired, 
  cloacal 
  

   opening 
  more 
  longitudinal 
  than 
  round, 
  never 
  transverse. 
  Oviparous." 
  The 
  skull 
  is 
  more 
  

   sohd 
  and 
  compact 
  than 
  in 
  other 
  reptilian 
  orders. 
  The 
  carapace 
  (upper 
  half 
  of 
  shell) 
  and 
  

   plastron 
  (lower 
  half 
  of 
  shell) 
  are 
  usually 
  connected 
  by 
  a 
  bony 
  bridge. 
  In 
  some 
  species, 
  how- 
  

   ever, 
  a 
  ligamentous 
  hinge 
  divides 
  the 
  plastron 
  so 
  that 
  one 
  or 
  both 
  parts 
  are 
  movable 
  as 
  in 
  the 
  

   Box 
  Tortoise. 
  In 
  the 
  genus 
  Cinixys 
  (of 
  the 
  Old 
  World) 
  a 
  similar 
  hinge 
  extends 
  across 
  the 
  

   carapace, 
  the 
  posterior 
  portion 
  being 
  movable. 
  The 
  neck, 
  which 
  may 
  be 
  completely 
  or 
  only 
  

   partially 
  withdrawn 
  into 
  the 
  shell, 
  is 
  an 
  important 
  factor 
  in 
  classification, 
  for 
  in 
  some 
  forms 
  

   it 
  is 
  simply 
  folded 
  sideways 
  (Pleurodira) 
  while 
  in 
  others 
  it 
  is 
  retracted 
  in 
  a 
  sigmoid 
  curve 
  in 
  

   the 
  vertical 
  plane. 
  The 
  various 
  shades 
  and 
  degrees 
  of 
  colors 
  (black, 
  yellow, 
  or 
  red) 
  in 
  turtles 
  

   are 
  due 
  to 
  a 
  pigment 
  formed 
  in 
  the 
  Malpighian 
  layer 
  of 
  the 
  skin. 
  The 
  digestive 
  apparatus 
  

   is 
  simple. 
  The 
  relative 
  length 
  of 
  the 
  different 
  portions 
  of 
  the 
  intestinal 
  tract 
  in 
  different 
  species 
  

   varies 
  to 
  a 
  Considerable 
  extent, 
  so 
  much 
  so 
  that 
  it 
  also 
  becomes 
  a 
  factor 
  in 
  classification. 
  Louis 
  

   Agassiz 
  in 
  his 
  Contributions 
  to 
  the 
  Natural 
  History 
  of 
  the 
  ITnited 
  States 
  of 
  America 
  (1857, 
  

   vol. 
  1, 
  p. 
  279) 
  gives 
  an 
  interesting 
  table 
  illustrating 
  some 
  of 
  these 
  variations. 
  Agassiz 
  calls 
  

  

  