﻿98 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  The 
  figure 
  29 
  is 
  the 
  result 
  of 
  the 
  preceding 
  considerations, 
  but 
  it 
  is 
  not 
  to 
  be 
  consid- 
  

   ered 
  as 
  completely 
  demonstrated. 
  They 
  all 
  go 
  to 
  show 
  the 
  narrow 
  and 
  prominent 
  form 
  

   of 
  the 
  abdominal 
  region, 
  which 
  was 
  associated 
  with 
  its 
  posterior 
  position, 
  and 
  the 
  great 
  

   lengths 
  of 
  the 
  femora. 
  Fig. 
  a 
  is 
  a 
  front 
  view 
  of 
  the 
  pubis 
  ; 
  b 
  is 
  an 
  internal 
  view 
  of 
  the 
  

   ischium 
  of 
  Clepsysaurus. 
  

  

  Dentition. 
  — 
  The 
  teeth 
  of 
  this 
  genus 
  are 
  very 
  much 
  smaller 
  in 
  relation 
  to 
  the 
  size 
  of 
  

   the 
  animal 
  than 
  in 
  Iguanodon. 
  They 
  bear 
  enamel 
  on 
  one 
  surface 
  only, 
  the 
  external 
  for 
  

   the 
  inferior 
  series 
  as 
  Leidy 
  points 
  out. 
  Thus 
  but 
  one 
  edge 
  of 
  the 
  worn 
  crowns 
  is 
  enam- 
  

   elled, 
  and 
  acts 
  functionally 
  like 
  that 
  of 
  the 
  anterior 
  faces 
  of 
  the 
  incisors 
  of 
  Rodents. 
  They 
  

   produce 
  shear-like 
  edges, 
  cutting 
  the 
  vegetable 
  food 
  by 
  a 
  horizontal 
  transverse 
  motion. 
  

  

  HADROSAURUS 
  MIRABILIS, 
  Leidy. 
  

  

  Proceed. 
  A. 
  N. 
  Sei., 
  Phil., 
  1868, 
  199. 
  

  

  Trachodon 
  mirabilis, 
  Trans. 
  Am. 
  Phil. 
  Soe., 
  XI, 
  1860, 
  140. 
  Tab. 
  

  

  Upper 
  Jurassic 
  Bad 
  Lands 
  of 
  Judith 
  River, 
  Nebraska. 
  

  

  Known 
  from 
  teeth, 
  and 
  perhaps 
  vertebras 
  and 
  phalanges. 
  

  

  HADROSAURUS 
  FOULKII, 
  Leidy. 
  

  

  Proc. 
  Acad. 
  Nat. 
  Sci., 
  Phil., 
  1858, 
  218, 
  Cret. 
  Eept. 
  U. 
  S. 
  76, 
  Tab. 
  XII 
  to 
  XVII. 
  

   Cretaceous 
  green 
  sand, 
  New 
  Jersey. 
  

  

  There 
  are 
  eight 
  localities 
  in 
  the 
  green 
  sand 
  of 
  Cretaceous 
  age 
  in 
  New 
  Jersey, 
  from 
  

   which 
  I 
  have 
  seen 
  portions 
  of 
  this 
  species. 
  

  

  HADROSAURUS 
  ?OCCIDENTALIS, 
  Leidy. 
  

  

  Thespesius 
  occidentalis. 
  Trans. 
  Amer. 
  Philoso. 
  Soc, 
  XI., 
  1860, 
  151, 
  tab. 
  

   ? 
  Cretaceous 
  Beds 
  of 
  Nebraska, 
  between 
  Moreau 
  and 
  Grand 
  Rivers. 
  

  

  Of 
  this 
  supposed 
  species, 
  Leidy 
  says, 
  "Had 
  the 
  remains 
  of 
  Thespesius 
  and 
  Trachodon 
  been 
  found 
  inn 
  deposit 
  of 
  

   the 
  same 
  age, 
  I 
  should 
  have 
  unhesitatingly 
  referred 
  them 
  to 
  the 
  same 
  animal, 
  and 
  I 
  cannot 
  avoid 
  the 
  suspicion 
  that 
  

   future 
  investigation 
  may 
  determine 
  them 
  to 
  be 
  the 
  same." 
  In 
  this 
  he 
  refers 
  to 
  Hadrosaurus 
  mirabilis, 
  which 
  Hayden 
  

   discovered 
  in 
  the 
  Jurassic 
  of 
  Judith 
  River, 
  while 
  the 
  types 
  of 
  Thespesius 
  were 
  found 
  by 
  the 
  same 
  geologist, 
  in 
  a 
  bed 
  

   with 
  other 
  vertebrates, 
  mostly 
  reptiles, 
  which 
  he 
  determined 
  to 
  be 
  of 
  Miocene 
  age. 
  

  

  Now, 
  the 
  extreme 
  improbability 
  of 
  this 
  type 
  occurring 
  in 
  a 
  Miocene 
  bed 
  will 
  occur 
  to 
  many 
  palaeontologists, 
  as 
  

   has 
  to 
  me. 
  With 
  the 
  view 
  of 
  determining 
  this 
  point 
  if 
  possible, 
  I 
  instituted 
  an 
  examination 
  of 
  the 
  forms 
  brought 
  by 
  

   Dr. 
  Hayden 
  from 
  this 
  locality, 
  and 
  first 
  of 
  that 
  most 
  characteristic 
  animal, 
  the 
  Ischyrotherium, 
  of 
  Leidy. 
  This, 
  as 
  

   has 
  appeared 
  in 
  the 
  preceding 
  pages, 
  I 
  believe 
  to 
  be 
  a 
  reptile, 
  allied 
  to 
  Plesiosaurus, 
  a 
  conclusion 
  which 
  at 
  once 
  estab- 
  

   lishes 
  the 
  Mesozic 
  age 
  of 
  the 
  bed. 
  It 
  coincides 
  with 
  the 
  presence 
  of 
  Hadrosaurus, 
  in 
  indicating 
  Cretaceous 
  or 
  upper 
  

   Jurassic 
  age. 
  

  

  