﻿166 
  

  

  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  The 
  plastron 
  of 
  this 
  species 
  is 
  relatively 
  much 
  thinner 
  than 
  in 
  the 
  other 
  species 
  of 
  the 
  genus. 
  

   A 
  sternum, 
  probably, 
  of 
  this 
  species, 
  is 
  in 
  my 
  collection. 
  It 
  is 
  unfortunately 
  without 
  the 
  xiphisternal 
  pieces, 
  but 
  

   conforms 
  in 
  all 
  respects 
  with 
  what 
  we 
  know 
  of 
  P. 
  sulcatus. 
  Its 
  surface 
  has 
  been 
  injured 
  by 
  pyrites. 
  It 
  is 
  character- 
  

   Fig. 
  45. 
  ized 
  by 
  its 
  thinness 
  and 
  general 
  lightness, 
  as 
  well 
  as 
  

  

  by 
  the 
  singular 
  form 
  of 
  the 
  hyosternal 
  element. 
  

   The 
  remains 
  consist 
  of 
  a 
  large 
  portion 
  of 
  the 
  plas- 
  

   tron, 
  and 
  two 
  costal 
  bones, 
  found 
  in 
  the 
  marl 
  ex- 
  

   cavations 
  of 
  the 
  "West 
  Jersey 
  Company, 
  near 
  Bames- 
  

   boro. 
  

  

  The 
  external 
  surface 
  of 
  the 
  plastron 
  exhibits 
  

   neither 
  sculpture 
  nor 
  impression 
  of 
  sutures 
  of 
  

   scutes. 
  It 
  is 
  slightly 
  rugose 
  in 
  some 
  places. 
  The 
  

   free 
  margin 
  at 
  the 
  axillary 
  and 
  inguinal 
  regions 
  is 
  

   obtuse, 
  but 
  becomes 
  thin 
  a 
  little 
  distance 
  before 
  

   reaching 
  the 
  episternal 
  and 
  xiphisternal 
  sutures, 
  re- 
  

   spectively. 
  

  

  The 
  suture 
  between 
  the 
  hyo- 
  and 
  hyposternals 
  is 
  

   straight 
  and 
  fine, 
  while 
  that 
  between 
  hypo- 
  and-xi- 
  

   phisternals 
  is 
  straight 
  and 
  coarse. 
  The 
  longitudinal 
  

   median 
  suture 
  is 
  irregular 
  and 
  very 
  coarse. 
  That 
  

   between 
  hyo- 
  and 
  epistemum 
  is 
  remarkable 
  in 
  its 
  

   direction, 
  thus 
  distinguishing 
  the 
  species 
  from 
  Ado- 
  

   cus. 
  pravus, 
  with 
  which 
  this 
  plastron 
  might 
  oth- 
  

   erwise 
  be 
  compared. 
  It 
  advances 
  posteriorly 
  on 
  the 
  

   outer 
  part 
  of 
  the 
  hyosternal, 
  causing 
  its 
  junction 
  with 
  

   the 
  margin 
  to 
  be 
  an 
  inch 
  behind 
  its 
  junction 
  with 
  the 
  

   mesosternum 
  ; 
  the 
  reverse 
  is 
  the 
  usual 
  relation 
  in 
  

   tortoises. 
  

  

  The 
  bones 
  of 
  the 
  plastron, 
  while 
  more 
  than 
  half 
  

   as 
  wide 
  again 
  as 
  those 
  of 
  A. 
  beatus, 
  are 
  medi- 
  

   ally 
  scarcely 
  half 
  so 
  thick; 
  the 
  thickness 
  increases 
  to 
  

   within 
  a 
  certain 
  distance 
  of 
  the 
  outer 
  margin. 
  

  

  The 
  accompanying 
  restoration 
  of 
  the 
  plastron 
  is 
  

   merely 
  designed 
  to 
  illustrate 
  the 
  form 
  and 
  characters 
  of 
  the 
  sutures 
  described. 
  The 
  outlines 
  of 
  the 
  mesosternum 
  are 
  

   erroneous; 
  the 
  piece 
  is 
  longitudinal, 
  not 
  tranverse; 
  it 
  had 
  not 
  been 
  obtained 
  at 
  the 
  time 
  the 
  cut 
  was 
  made. 
  

  

  Measurements. 
  

   Total 
  width 
  plastron 
  externally, 
  within 
  elevations 
  of 
  bridges, 
  

   Length 
  hyosternal, 
  on 
  margins, 
  from 
  first 
  rise 
  at 
  axilla 
  to 
  episternal 
  suture, 
  

   From 
  latter 
  to 
  mesosternal 
  suture, 
  

   Thickness 
  hyosternal 
  at 
  middle 
  sut., 
  

   " 
  hyposternal 
  " 
  " 
  

  

  In. 
  

  

  Lin. 
  

  

  11 
  

  

  10. 
  

  

  3 
  

  

  8. 
  

  

  1 
  

  

  10.75 
  

  

  

  4.25 
  

  

  

  2.8 
  

  

  TArHROSPHYS 
  LESLIANUS, 
  Cope. 
  

  

  This 
  is 
  a 
  smaller 
  and 
  more 
  delicate 
  species 
  than 
  the 
  last, 
  and 
  differs 
  in 
  many 
  particulars. 
  It 
  is 
  found 
  on 
  a 
  single 
  

   individual, 
  which, 
  though 
  not 
  more 
  than 
  half 
  the 
  size 
  of 
  the 
  T. 
  sulcatus, 
  is 
  evidently 
  adult. 
  The 
  portions 
  preserved 
  

   are 
  a 
  considerable 
  number 
  of 
  the 
  element 
  of 
  carapace 
  and 
  plastron, 
  but 
  none 
  other. 
  The 
  union 
  of 
  the 
  costal 
  and 
  

   marginal 
  bones 
  is 
  complete. 
  The 
  fir&t 
  costal 
  has 
  the 
  same 
  form 
  as 
  in 
  T. 
  molops, 
  bearing 
  as 
  usual, 
  a 
  crest 
  representing 
  

  

  