﻿DIAMOND-BACK 
  TERRAPIN. 
  381 
  

  

  spotted 
  with 
  black. 
  The 
  head, 
  neck, 
  and 
  extremities 
  are 
  gray, 
  spotted 
  with 
  black, 
  especially 
  

   well 
  marked 
  on 
  the 
  neck. 
  

  

  Description. 
  — 
  Each 
  shield 
  of 
  the 
  carapace 
  contains 
  a 
  nmnber 
  of 
  concentric 
  grooves, 
  rising 
  

   in 
  step-like 
  fashion. 
  There 
  is 
  a 
  well-defined 
  blunt 
  tuberculated 
  keel. 
  In 
  old 
  individuals 
  

   these 
  concentric 
  rings 
  completely 
  disappear, 
  leaving 
  a 
  smooth 
  shell. 
  There 
  are 
  no 
  scales 
  on 
  

   the 
  neck, 
  upper 
  arms, 
  or 
  thighs. 
  The 
  horny 
  sheath 
  of 
  the 
  jaws 
  is 
  straight, 
  strong, 
  and 
  smooth; 
  

   and 
  the 
  alveolar 
  surface 
  flat, 
  broad, 
  and 
  without 
  ridges. 
  In 
  his 
  revision 
  of 
  the 
  genus 
  Mala- 
  

   clemys, 
  W. 
  P. 
  Hay 
  (1905) 
  gives 
  the 
  following 
  characteristics 
  for 
  this 
  subspecies: 
  "The 
  cara- 
  

   pace 
  has 
  in 
  general 
  the 
  form 
  of 
  that 
  of 
  M. 
  centrata, 
  but 
  is 
  broader 
  posteriorly 
  and 
  the 
  marginal 
  

   plates 
  behind 
  the 
  bridge 
  are 
  seldom 
  revolute; 
  the 
  plastron, 
  also, 
  is 
  less 
  convergent 
  posteriorly; 
  

   the 
  plates 
  of 
  the 
  carapace 
  bear 
  conspicuous 
  concentric 
  ridges, 
  but 
  those 
  of 
  the 
  plastron 
  are 
  

   smoother, 
  nearly 
  always, 
  however, 
  except 
  in 
  some 
  old 
  individuals, 
  showing 
  at 
  least 
  traces 
  of 
  

   the 
  Unes 
  of 
  growth; 
  the 
  head 
  is 
  small, 
  narrow, 
  and 
  neatly 
  formed, 
  the 
  top 
  of 
  it 
  flat, 
  givmg 
  the 
  

   nose 
  a 
  sharper 
  appearance 
  than 
  is 
  to 
  be 
  seen 
  in 
  the 
  other 
  form 
  of 
  this 
  species. 
  

  

  "The 
  color 
  varies 
  from 
  uniform 
  black 
  to 
  Ught 
  brown, 
  the 
  latter 
  always 
  marked 
  with 
  darker 
  

   concentric 
  lines 
  on 
  eaich 
  plate 
  of 
  the 
  carapace 
  and 
  more 
  or 
  less 
  blotched 
  with 
  darker 
  on 
  the 
  

   plastron; 
  the 
  skin 
  of 
  the 
  head, 
  legs, 
  and 
  tail 
  varies 
  from 
  nearly 
  pure 
  black 
  to 
  a 
  very 
  Ught 
  green- 
  

   gray, 
  the 
  latter 
  more 
  or 
  less 
  marked 
  with 
  specks 
  and 
  short, 
  crooked 
  hues 
  of 
  black; 
  the 
  hps 
  

   and 
  top 
  of 
  the 
  head 
  are 
  usually 
  dusky, 
  but 
  individuals 
  may 
  be 
  found 
  wdth 
  either 
  or 
  both 
  white. 
  

  

  "The 
  males 
  resemble 
  the 
  females 
  in 
  the 
  shape 
  of 
  the 
  carapace, 
  except 
  that 
  they 
  are 
  a 
  

   little 
  sharper 
  posteriorly 
  and 
  the 
  marginal 
  plates 
  are 
  frequently 
  a 
  little 
  revolute; 
  the 
  nose 
  is 
  

   much 
  sharper 
  than 
  in 
  the 
  females." 
  

  

  Of 
  the 
  differences 
  in 
  sex 
  he 
  says: 
  "The 
  sexual 
  differences 
  . 
  . 
  . 
  aside 
  from 
  the 
  genital 
  parts, 
  

   are 
  greater 
  than 
  in 
  any 
  other 
  group 
  of 
  turtles 
  known 
  to 
  me. 
  The 
  females 
  are 
  much 
  larger 
  

   than 
  the 
  males, 
  they 
  alone 
  attaining 
  the 
  sizes 
  usually 
  cited 
  in 
  descriptions. 
  Their 
  heads 
  are 
  

   heavier 
  and 
  less 
  pointed, 
  their 
  bodies 
  deeper, 
  and 
  their 
  tails 
  shorter. 
  The 
  males 
  seldom, 
  if 
  

   ever, 
  reach 
  a 
  greater 
  length 
  than 
  5 
  inches; 
  the 
  shell 
  is 
  flatter 
  than 
  that 
  of 
  the 
  female, 
  and 
  

   posteriorly 
  more 
  triangular; 
  the 
  marginal 
  plates 
  are 
  apt 
  to 
  be 
  revolute, 
  the 
  head 
  is 
  smaller, 
  

   the 
  nose 
  sharper, 
  and 
  the 
  tail 
  longer." 
  

  

  Malformations 
  have 
  been 
  commonly 
  noted 
  in 
  this 
  species. 
  Coker 
  (1910) 
  found 
  a 
  great 
  

   diversity 
  in 
  the 
  scutes, 
  also 
  in 
  the 
  shape 
  and 
  size 
  of 
  eggs 
  and 
  of 
  young, 
  boldness, 
  habits 
  of 
  

   feeding 
  and 
  of 
  hibernating, 
  in 
  moulting, 
  and 
  in 
  rate 
  of 
  growth. 
  Females 
  show 
  a 
  greater 
  divers- 
  

   ity 
  than 
  males. 
  

  

  Rate 
  of 
  Groivth. 
  — 
  Measuring 
  about 
  one 
  inch 
  (length 
  of 
  plastron) 
  at 
  bu-th, 
  young 
  Terrapins 
  

   increase 
  in 
  length 
  about 
  one 
  inch 
  each 
  year 
  for 
  the 
  first 
  two 
  years, 
  slightly 
  less 
  for 
  the 
  third 
  

   and 
  about 
  one-half 
  inch 
  for 
  each 
  of 
  the 
  fourth 
  and 
  fifth 
  years. 
  This 
  rate 
  is 
  variable, 
  however, 
  

   few 
  six-inch 
  Terrapins 
  being 
  less 
  than 
  seven 
  years 
  of 
  age. 
  As 
  to 
  manner 
  of 
  growth, 
  Coker 
  

  

  