﻿156 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  B. 
  Kinne, 
  Director 
  of 
  the 
  Squankum 
  Company's 
  marl 
  excavations, 
  Squankum, 
  Monmouth 
  

   County, 
  N. 
  J. 
  

  

  PLETJRODIRA. 
  

  

  This 
  division 
  of 
  the 
  order, 
  now 
  found 
  only 
  in 
  the 
  southern 
  hemisphere, 
  had, 
  in 
  Meso- 
  

   zoic 
  and 
  Cainozoic 
  time, 
  as 
  is 
  known 
  to 
  geologists, 
  a 
  much 
  more 
  extended 
  distribution. 
  

   It 
  has 
  presented 
  to 
  various 
  naturalists 
  the 
  appearance 
  of 
  a 
  repetition 
  under 
  another 
  type 
  

   of 
  structure, 
  of 
  the 
  groups 
  of 
  Cryptodira. 
  Agassiz, 
  in 
  his 
  contributions 
  to 
  the 
  Natural 
  His- 
  

   tory 
  of 
  the 
  United 
  States, 
  Vol. 
  I., 
  states 
  that 
  he 
  believes 
  it 
  to 
  form 
  a 
  series 
  of 
  families 
  

   parallel 
  with 
  those 
  of 
  the 
  other 
  suborder 
  ; 
  but 
  he 
  does 
  not 
  attempt 
  to 
  define 
  them. 
  He 
  

   gives 
  as 
  types 
  of 
  these 
  families 
  Chelys, 
  Sternothaerus, 
  Pelomedusa, 
  Hydraspis, 
  Chelodina, 
  

   and 
  Podocnemis. 
  After 
  some 
  examination 
  of 
  their 
  structure, 
  assisted 
  by 
  an 
  essay 
  on 
  

   their 
  cranial 
  characters 
  by 
  Dr. 
  Gray,* 
  I 
  believe 
  that 
  four 
  such 
  families 
  exist, 
  the 
  types 
  

   of 
  which 
  are 
  Pelomedusa, 
  Sternothaerus, 
  Hydraspis, 
  and 
  Podocnemis. 
  I 
  have 
  al- 
  

   ready 
  indicated 
  the 
  fact 
  that 
  Pelomedusa 
  has 
  the 
  foot 
  ' 
  of 
  the 
  Testudinidae. 
  I 
  

   also 
  find 
  that 
  it 
  has 
  the 
  rudimental 
  interstemal 
  bone, 
  as 
  figured 
  by 
  Wagler 
  in 
  

   Podocnemis, 
  and 
  that 
  Sternothaerus 
  has 
  this 
  bone 
  complete 
  on 
  each 
  side, 
  en- 
  

   tirely 
  separating 
  the 
  hyo- 
  and 
  hyposternals, 
  as 
  in 
  the 
  extinct, 
  and 
  till 
  now 
  uncharacterized 
  

   family 
  of 
  the 
  Pleurosternidae. 
  The 
  Hydraspididae 
  have 
  neither 
  this 
  bone 
  nor 
  a 
  zygo- 
  

   matic 
  arch, 
  but 
  a 
  peculiar 
  parieto-mastoid 
  arch, 
  as 
  in 
  the 
  Chamaeleons. 
  These 
  characters 
  

   are 
  shared 
  by 
  Chelys, 
  Chelodina 
  and 
  others. 
  Podocnemis 
  adds 
  to 
  the 
  zygomatic 
  arch, 
  

   the 
  lateral-intersternal 
  bone, 
  an 
  Emydoid 
  foot, 
  and 
  no 
  parieto-mastoid 
  arch. 
  

  

  The 
  extinct 
  species 
  of 
  the 
  Pleurodira, 
  as 
  yet 
  found 
  in 
  Europe, 
  belong 
  to 
  the 
  Sterno- 
  

   thaeridae 
  and 
  Podocnemididae. 
  This 
  I 
  have 
  readily 
  determined 
  from 
  the 
  good 
  descrip- 
  

   tions 
  and 
  figures 
  given 
  by 
  Professor 
  Owen 
  in 
  the 
  Paleontographical 
  Society's 
  volumes. 
  

  

  STERNOTHAEEIDAE. 
  

  

  To 
  this 
  family 
  belongs 
  the 
  Platemys 
  bullockii 
  Owen, 
  from 
  the 
  lower 
  Eocene. 
  It 
  repre- 
  

   sents 
  a 
  genus 
  which 
  I 
  call 
  Digerrhum, 
  which 
  differs 
  from 
  Sternothaerus 
  in 
  having 
  the 
  an- 
  

   terior 
  lobe 
  of 
  the 
  sternum 
  immobile, 
  and 
  two 
  ranges 
  of 
  marginal 
  plates, 
  as 
  in 
  Pleuroster- 
  

   num 
  and 
  Chelone. 
  

  

  PODOCNEMIDIDAE. 
  

  

  To 
  this 
  family 
  belong 
  Emys 
  laevis 
  and 
  Platemys 
  bowerbanlcii 
  of 
  Owen, 
  who 
  com- 
  

   pares 
  the 
  latter 
  species 
  to 
  Podocnemis. 
  So 
  far 
  as 
  I 
  can 
  see 
  they 
  both 
  appear 
  to 
  belong 
  

   to 
  the 
  genus 
  Podocnemis, 
  and 
  may 
  be 
  called 
  Podocnemis 
  laevis, 
  and 
  P. 
  bowerbankii. 
  

  

  To 
  this 
  family 
  may 
  perhaps 
  also 
  belong 
  the 
  genus. 
  

  

  *Proc. 
  Zool. 
  Soc. 
  London, 
  1864. 
  

  

  