﻿150 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  Ft. 
  

  

  In. 
  

  

  6 
  

  

  10. 
  

  

  2 
  

  

  8.5 
  

  

  The 
  broad, 
  regular 
  alveolar 
  surfaces 
  have 
  no 
  doubt 
  supported 
  a 
  massive 
  corneous 
  table, 
  in 
  some 
  degree 
  like 
  that 
  

   of 
  Platypeltis 
  ferox, 
  and 
  with 
  little 
  or 
  no 
  external 
  cutting 
  margin. 
  This 
  arrangement, 
  as 
  well 
  as 
  the 
  compactness 
  

   of 
  structure, 
  are 
  appropriate 
  to 
  a 
  nutrition 
  dependent 
  on 
  crushing 
  more 
  or 
  less 
  hard 
  bodies, 
  as 
  molluscus. 
  That 
  the 
  

   Ostreae, 
  Terebratulae, 
  etc., 
  of 
  the 
  sea 
  coasts 
  or 
  estuaries 
  in 
  which 
  it 
  lived 
  formed 
  much 
  of 
  its 
  food, 
  is 
  therefore 
  quite 
  

   probable. 
  

  

  Estimating 
  the 
  proportions 
  to 
  have 
  been 
  similar 
  to 
  those 
  of 
  Chelydra 
  serpentina, 
  * 
  the 
  dimensions 
  of 
  the 
  Euclas- 
  

   tes 
  platyops 
  were 
  

  

  Length 
  from 
  end 
  muzzle 
  to 
  end 
  tail, 
  

   ' 
  ' 
  of 
  carapace, 
  

  

  This 
  species 
  belongs 
  most 
  probably 
  to 
  one 
  of 
  the 
  genera 
  of 
  the 
  same 
  type 
  here 
  de- 
  

   scribed, 
  but 
  whether 
  to 
  Peritresius, 
  Propleura 
  or 
  Osteopygis, 
  is 
  not 
  as 
  yet 
  ascertainable. 
  

   In 
  any 
  case, 
  Euclastes 
  is 
  an 
  older 
  name 
  than 
  either 
  of 
  the 
  above. 
  

  

  PERITRESIUS, 
  Cope. 
  

  

  This 
  genus 
  is 
  proposed 
  to 
  express 
  the 
  characters 
  of 
  the 
  Chelone 
  ornata 
  of 
  Leidy. 
  

   Nothing 
  is 
  known 
  of 
  the 
  species 
  but 
  a 
  costal 
  and 
  parts 
  of 
  two 
  adjacent 
  marginal 
  bones. 
  

   These 
  are 
  covered 
  with 
  coarse 
  tubercles, 
  as 
  in 
  some 
  Trionyx, 
  and 
  more 
  as 
  in 
  Prochonias 
  

   nodosus. 
  There 
  are 
  no 
  dermal 
  sutures 
  on 
  the 
  specimens, 
  and 
  it 
  is 
  not 
  probable 
  that 
  

   the 
  dermal 
  covering 
  was 
  corneous 
  or 
  scutiform. 
  The 
  pit 
  for 
  the 
  rib 
  is 
  very 
  small 
  and 
  flat, 
  

   and 
  not 
  at 
  all 
  as 
  in 
  Chelone. 
  Were 
  it 
  not 
  that 
  the 
  head 
  of 
  the 
  rib 
  is 
  not 
  so 
  flattened 
  as 
  

   in 
  Trionychidae, 
  I 
  should 
  imagine 
  the 
  genus 
  might 
  be 
  allied 
  to 
  Emyda, 
  or 
  the 
  Trionyches, 
  

   Avith 
  marginal 
  bones. 
  With 
  our 
  present 
  knowledge, 
  it 
  is 
  better 
  that 
  the 
  costal 
  bone 
  should 
  

   remain 
  near 
  Peritresius. 
  

  

  The 
  structure 
  of 
  the 
  costal 
  bone 
  above 
  the 
  inferior 
  or 
  costal 
  layers 
  is 
  vesicular. 
  The 
  

   entire 
  freedom 
  of 
  the 
  marginal 
  bone 
  separates 
  the 
  form 
  from 
  any 
  of 
  our 
  known 
  Plcurcdira. 
  

  

  PERITRESIUS 
  ORNATUS, 
  Leidy. 
  

  

  C7telone 
  ornata, 
  Leidy, 
  Proc. 
  A. 
  N. 
  Sci., 
  18S6, 
  303 
  Cretaceous 
  Kept., 
  1. 
  c. 
  

  

  Marginal 
  bones, 
  covered 
  with 
  coarse 
  tubercles 
  in 
  the 
  middle, 
  and 
  coarse 
  ridges 
  near 
  the 
  sutures, 
  which 
  are 
  wider 
  

   than 
  the 
  intervals 
  between 
  them. 
  

  

  New 
  Jersey. 
  

  

  TRIONYCHIDAE. 
  

  

  Seven 
  species 
  of 
  this 
  family 
  have 
  been 
  found 
  in 
  the 
  North 
  American 
  strata, 
  all 
  

   referable 
  to 
  

  

  * 
  Compared 
  Inapposltoly 
  with 
  ttydraspis 
  martmiliani 
  in 
  tlie 
  original 
  description. 
  

  

  