﻿AND 
  AYES 
  OF 
  NORTH 
  AMERICA. 
  129 
  

  

  It 
  also 
  possesses 
  a 
  character 
  of 
  Pleurosternum 
  in 
  the 
  presence 
  of 
  a 
  series 
  of 
  marginal 
  

   dermal 
  plates 
  on 
  the 
  sternal 
  bridge. 
  It 
  belongs 
  to 
  the 
  true 
  Emydidae, 
  having 
  the 
  eight 
  

   paired 
  sternal 
  bones 
  instead 
  of 
  ten 
  of 
  the 
  first 
  mentioned. 
  The 
  markings 
  of 
  the 
  dermal 
  

   plates 
  of 
  the 
  plastron 
  are 
  not 
  distinct. 
  

  

  ADOCUS 
  BEATUS, 
  Leidy. 
  

  

  Emys 
  beatus, 
  Leidy, 
  Cretaceous 
  Reptiles, 
  Smithson. 
  Contrih. 
  1804, 
  107. 
  

  

  Remains 
  of 
  a 
  considerable 
  portion 
  of 
  the 
  plastron 
  and 
  carapace 
  of 
  this 
  species 
  from 
  

   the 
  marl 
  excavations 
  of 
  David 
  Haines 
  near 
  Medford, 
  N. 
  J., 
  furnish 
  important 
  characters, 
  

   as 
  already 
  indicated. 
  The 
  posterior 
  lobe 
  of 
  the 
  sternum 
  is 
  long 
  and 
  flat, 
  and 
  strongly 
  

   emarginate 
  behind; 
  its 
  greatest 
  length 
  is 
  5 
  in. 
  9 
  lin., 
  greatest 
  (anterior) 
  width 
  5 
  in. 
  8 
  lin. 
  

   The 
  thickness 
  of 
  the 
  hyosternal 
  bones 
  is 
  a 
  little 
  greater 
  at 
  the 
  sides 
  than 
  at 
  the 
  median 
  

   portion 
  ; 
  latter 
  measurement 
  7 
  lines 
  ; 
  all 
  the 
  pieces 
  of 
  the 
  plastron 
  are 
  thicker 
  than 
  those 
  

   of 
  the 
  carapace. 
  

  

  The 
  anterior 
  lobe 
  of 
  the 
  sternum 
  in 
  A. 
  beatus 
  would 
  appear 
  to 
  have 
  been 
  more 
  or 
  

   less 
  moveable. 
  

  

  ADOCUS 
  PRAVUS, 
  Leidy. 
  

  

  Emys.pravus, 
  Leidy, 
  Proceed. 
  Ac. 
  Nat. 
  Sci., 
  1856, 
  312, 
  Cretaceous 
  Rept. 
  Tab. 
  

   Middlebed, 
  or 
  uppe?; 
  Cretaceous 
  green 
  sand 
  New 
  Jersey. 
  

  

  This 
  species 
  is 
  referred 
  here 
  because 
  of 
  its 
  general 
  resemblance 
  to 
  the 
  others 
  of 
  the 
  

   genus. 
  Its 
  costal 
  bones 
  have 
  not 
  yet 
  been 
  procured. 
  

  

  PLEUROSTERNUM, 
  Bell. 
  

  

  Some 
  of 
  the 
  Emydinae 
  of 
  the 
  New 
  Jersey 
  Green 
  Sand 
  exhibit 
  only 
  faint 
  impressions 
  

   of 
  the 
  usual 
  horny 
  dermal 
  plates. 
  It 
  is 
  probable 
  therefore 
  that 
  such 
  Avere 
  covered 
  

   with 
  coriaceous 
  plates 
  as 
  in 
  the 
  genus 
  Dermatemys 
  and 
  some 
  species 
  of 
  Hydraspididae. 
  

  

  The 
  species 
  which 
  is 
  referred 
  to 
  Dermatemys, 
  D. 
  mavei 
  Gray 
  from 
  Mexico, 
  is 
  further 
  

   distinguished 
  generically 
  by 
  a 
  series 
  of 
  marginal 
  plates 
  between 
  the 
  axilla 
  and 
  groin 
  on 
  

   each 
  side, 
  within 
  the 
  usual 
  marginal 
  series. 
  The 
  same 
  peculiarity 
  characterizes 
  also 
  the 
  

   genus 
  Macrochelys, 
  Avhich 
  has 
  however 
  no 
  affinity 
  with 
  the 
  present. 
  

  

  The 
  hyosternal 
  bones, 
  quite 
  perfectly 
  preserved, 
  of 
  an 
  aquatic 
  tortoise, 
  from 
  the 
  farm 
  

   of 
  David 
  Haines 
  near 
  Medford, 
  present 
  the 
  double 
  marginal 
  series 
  of 
  Dermatemys. 
  It 
  

   differs 
  from 
  the 
  species 
  of 
  that 
  genus 
  in 
  the 
  apparent 
  fusion 
  of 
  the 
  pectoral 
  and 
  humeral 
  

   dermal 
  scuta, 
  a 
  peculiarity 
  which 
  I 
  have 
  not 
  seen 
  in 
  any 
  modern 
  genus 
  of 
  Emydidae 
  or 
  

   Hvdraspididae. 
  This 
  is 
  characteristic 
  of 
  Pleurosternum, 
  and 
  the 
  scuta 
  are 
  really 
  distinct, 
  

   the 
  pectoral 
  having 
  an 
  unusually 
  posterior 
  position, 
  on 
  account 
  of 
  the 
  intercalated 
  sternal 
  

  

  AMERI. 
  PHILOSO. 
  SOC 
  VOL. 
  XIV. 
  33 
  

  

  