﻿MUD 
  TURTLE. 
  363 
  

  

  Kinosternon 
  subrubrum 
  (Lacepede). 
  

  

  Mud 
  Turtle; 
  Fresh- 
  water 
  Box 
  Terrapin. 
  

   Plate 
  22. 
  

  

  Testudo 
  suhruhra 
  Lacepede, 
  Hist. 
  Nat. 
  Quadr. 
  Ovip. 
  Serp., 
  1788, 
  vol. 
  1, 
  Synops. 
  meth., 
  tabl. 
  betw. 
  pp. 
  618 
  

  

  and 
  619 
  (comp. 
  p. 
  132). 
  

   Kinosternon 
  suhritbrum 
  Stejneger 
  and 
  Barbour, 
  Check 
  List 
  No. 
  Amer. 
  Amph. 
  and 
  Rept., 
  1917, 
  p. 
  112. 
  

  

  The 
  Mud 
  Turtle 
  is 
  very 
  closely 
  allied 
  to 
  the 
  preceding 
  Musk 
  Turtle, 
  differing 
  chiefly 
  in 
  

   the 
  formation 
  and 
  size 
  of 
  the 
  plastron. 
  

  

  Size. 
  — 
  Adult 
  specimens 
  seldom 
  exceed 
  a 
  carapace 
  length 
  of 
  four 
  inches. 
  The 
  plastron 
  

   is 
  nearly 
  as 
  long 
  as 
  the 
  carapace. 
  The 
  measurements 
  of 
  a 
  specimen 
  in 
  the 
  Museum 
  of 
  Com- 
  

   parative 
  Zoology 
  at 
  Cambridge, 
  Massachusetts, 
  are: 
  length 
  of 
  carapace, 
  3f 
  inches; 
  width 
  of 
  

   carapace, 
  2J; 
  length 
  of 
  plastron, 
  3|; 
  width 
  of 
  plastron 
  at 
  anterior 
  hinge, 
  lit; 
  length 
  of 
  

   anterior 
  hinge, 
  Ig; 
  length 
  of 
  posterior 
  hinge, 
  1 
  J; 
  width 
  of 
  bridge, 
  ig; 
  width 
  of 
  head, 
  if. 
  

  

  Color. 
  — 
  The 
  upper 
  shell 
  is 
  dull 
  brown, 
  the 
  shields 
  sometimes 
  having 
  black 
  margins. 
  The 
  

   plastron 
  is 
  light 
  brown 
  or 
  yellowish. 
  The 
  head 
  is 
  brown 
  with 
  numerous 
  yellow 
  spots 
  on 
  the 
  

   neck, 
  sometimes 
  arranged 
  in 
  two 
  Unes 
  as 
  in 
  the 
  Musk 
  Turtle, 
  although 
  these 
  markings 
  are 
  

   not 
  constant. 
  There 
  are 
  small 
  horny 
  papillae 
  under 
  the 
  chin. 
  The 
  extremities 
  are 
  brown. 
  

  

  Description. 
  — 
  The 
  carapace, 
  which 
  is 
  completely 
  ossified, 
  is 
  broader 
  and 
  flatter 
  than 
  

   in 
  the 
  preceding 
  species, 
  being 
  wider 
  in 
  front 
  in 
  the 
  female 
  than 
  in 
  the 
  male. 
  The 
  head 
  also 
  

   is 
  not 
  as 
  large 
  proportionately 
  as 
  in 
  the 
  Musk 
  Turtle. 
  Both 
  jaws 
  have 
  sharp 
  cutting 
  edges. 
  

   The 
  plastron 
  in 
  this 
  species 
  is 
  large 
  and 
  nearly 
  covers 
  the 
  under 
  part 
  of 
  the 
  body. 
  It 
  is 
  com- 
  

   posed 
  of 
  eight 
  plates, 
  arranged 
  in 
  pairs, 
  through 
  which 
  a 
  median 
  suture 
  extends 
  without 
  inter- 
  

   ruption. 
  The 
  two 
  middle 
  pairs 
  of 
  plates 
  extend 
  entirely 
  across 
  the 
  body 
  and 
  are 
  sutured 
  to 
  

   the 
  carapace, 
  thus 
  forming 
  a 
  long 
  bridge. 
  The 
  anterior 
  and 
  posterior 
  pairs 
  of 
  plastral 
  plates 
  

   are 
  broad 
  and 
  rounded 
  and 
  are 
  joined 
  to 
  the 
  central 
  pairs 
  by 
  flexible 
  hinges 
  which 
  allow 
  the 
  

   two 
  ends 
  of 
  the 
  plastron 
  to 
  be 
  drawn 
  up 
  against 
  the 
  carapace 
  thus 
  protecting 
  the 
  soft 
  parts. 
  

   These 
  hinges 
  tend 
  to 
  ossify 
  in 
  very 
  old 
  specimens. 
  The 
  movable 
  parts 
  of 
  the 
  plastron 
  in 
  this 
  

   species 
  differ 
  from 
  those 
  of 
  the 
  true 
  Box 
  Tortoise 
  (Terrapene) 
  in 
  that 
  in 
  the 
  latter 
  one 
  hinge 
  

   divides 
  the 
  entire 
  plastron 
  transversely 
  into 
  halves 
  which 
  swing 
  upon 
  each 
  other, 
  while 
  in 
  

   the 
  former 
  they 
  swing 
  upon 
  "an 
  immovable 
  transverse 
  beam" 
  which 
  is 
  united 
  by 
  bony 
  sutui'es 
  

   to 
  the 
  carapace. 
  The 
  plastron 
  in 
  Terrapene 
  is 
  united 
  to 
  the 
  carapace 
  by 
  Ugamentous 
  attach- 
  

   ments 
  only. 
  The 
  feet 
  are 
  short 
  and 
  round, 
  and 
  the 
  toes 
  are 
  well 
  webbed. 
  The 
  tail 
  is 
  small 
  

   and 
  short, 
  but 
  longer 
  in 
  the 
  males, 
  and 
  terminates 
  in 
  a 
  horny 
  nail-Uke 
  point. 
  In 
  young 
  speci- 
  

   mens 
  the 
  carapace 
  shows 
  three 
  blunt 
  keels. 
  

  

  