﻿64 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  alveolus, 
  and 
  whose 
  development 
  had 
  occasioned 
  the 
  absorption 
  of 
  half 
  the 
  fang 
  of 
  the 
  functional 
  tooth. 
  On 
  the 
  basis 
  

   of 
  this 
  tooth 
  I 
  am 
  enabled 
  to 
  determine 
  the 
  distinctness 
  of 
  this 
  crocodile 
  from 
  the 
  T. 
  antiqua. 
  The 
  crown, 
  instead 
  of 
  

   being 
  like 
  that 
  species, 
  a 
  cone 
  with 
  a 
  circular 
  section, 
  with 
  a 
  narrow 
  cutting 
  longitudinal 
  ridge 
  rising 
  abruptly 
  from 
  

   the 
  surface 
  on 
  each 
  side, 
  in 
  this 
  tooth 
  has 
  a 
  lenticular 
  section, 
  with 
  the 
  cutting 
  ridges 
  on 
  the 
  acute 
  opposite 
  angles 
  . 
  

   Tbe 
  external 
  face 
  is 
  strongly 
  convex, 
  though 
  not 
  so 
  much 
  so 
  as 
  in 
  T. 
  antiqua. 
  The 
  edges 
  are 
  crenate, 
  but 
  not 
  so 
  as 
  

   to 
  produce 
  a 
  serration 
  of 
  the 
  margin. 
  Enamel 
  finely 
  obsoletely 
  striate. 
  

  

  The 
  vertebra 
  preserved 
  is 
  a 
  posterior 
  lumbar. 
  The 
  entire 
  coossification 
  of 
  the 
  neurapophysis 
  indicates 
  that 
  the 
  

   animal 
  is 
  adult 
  ; 
  their 
  upper 
  portions 
  are 
  lost. 
  The 
  diapophyses 
  have 
  had 
  an 
  oblique 
  basis, 
  rising 
  anteriorly, 
  their 
  

   middle 
  being 
  opposite 
  the 
  plane 
  of 
  the 
  neural 
  canal, 
  the 
  whole 
  length 
  standing 
  on 
  the 
  anterior 
  two-fifths 
  of 
  the 
  length 
  

   of 
  the 
  centrum. 
  The 
  cup 
  is 
  subcircular, 
  wider 
  transversely 
  ; 
  the 
  centrum 
  is 
  depressed 
  ; 
  below 
  broad, 
  with 
  a 
  median 
  

   longitudinal 
  concavity 
  ; 
  sides 
  vertical. 
  As 
  compared 
  with 
  the 
  dorsal 
  vertebrae 
  of 
  T. 
  antiqua, 
  the 
  latter 
  are 
  much 
  

   more 
  compressed 
  in 
  the 
  centrum 
  ; 
  and 
  although 
  the 
  posterior 
  lumbars 
  are 
  always 
  more 
  depressed 
  than 
  the 
  dorsals, 
  

   yet 
  the 
  present 
  seems 
  too 
  much 
  so 
  to 
  have 
  pertained 
  to 
  the 
  same 
  species. 
  It 
  differs 
  from 
  those 
  of 
  T. 
  antiqua 
  also, 
  

   in 
  that 
  the 
  floor 
  of 
  the 
  neural 
  canal 
  is 
  entirely 
  plane 
  and 
  smooth 
  ; 
  in 
  the 
  latter 
  it 
  is 
  deeply 
  grooved, 
  in 
  consequence 
  of 
  

   the 
  non-coalescence 
  of 
  the 
  expanded 
  bases 
  of 
  the 
  neurapophyses. 
  

  

  Ft. 
  

   Length 
  fragment 
  of 
  mandible, 
  

   Diameter 
  of 
  alveolus, 
  

   Axial 
  width 
  from 
  margin 
  alveolus 
  to 
  symphysis 
  above, 
  

  

  do. 
  do. 
  do. 
  do. 
  below, 
  

  

  Greatest 
  width 
  to 
  median 
  line 
  (behind), 
  

   Long 
  diameter 
  crown, 
  at 
  middle 
  of 
  length, 
  

   Width 
  muzzle, 
  

   Estimated 
  length 
  cranium, 
  

  

  do. 
  total 
  length, 
  33 
  

  

  Length 
  lumbar 
  vertebra 
  (centrum), 
  

   Width 
  cup, 
  

   Height 
  cup, 
  

  

  The 
  above 
  estimate 
  of 
  length 
  is 
  based 
  on 
  the 
  proportions 
  of 
  the 
  Gavialis 
  gangeticus 
  as 
  given 
  by 
  Cuvier. 
  

  

  THECACHAMPSA 
  ANTIQUA, 
  Leidy 
  sp. 
  

  

  Crocodilus 
  anliquus, 
  Leidy. 
  L. 
  c. 
  1851, 
  307. 
  Journ. 
  Ac. 
  N. 
  Sci., 
  II., 
  135. 
  Tab. 
  ? 
  Thecachampsa 
  contusor, 
  Cope. 
  

   Proc. 
  A. 
  N. 
  Sci., 
  1867, 
  143. 
  

  

  This 
  species 
  continues 
  as 
  yet 
  to 
  be 
  represented 
  only 
  by 
  the 
  specimens 
  on 
  which 
  it 
  was 
  based, 
  viz., 
  two 
  teeth, 
  two 
  

   vertebrae, 
  an 
  ungueal 
  phalange, 
  and 
  a 
  rib. 
  These 
  indicate 
  a 
  large 
  species 
  ; 
  the 
  vertebrae 
  are 
  even 
  larger 
  than 
  that 
  of 
  

   the 
  last, 
  and 
  the 
  teeth 
  will 
  not 
  enter 
  its 
  alveolae. 
  It 
  is 
  probably 
  the 
  largest 
  of 
  the 
  known 
  Crocodiles 
  of 
  this 
  country. 
  

   Fig. 
  16. 
  I 
  have 
  noticed 
  only 
  two 
  dentinal 
  cones 
  in 
  the 
  two 
  teeth 
  we 
  possess. 
  

  

  The 
  accompanying 
  outlines 
  are 
  those 
  of 
  sections 
  of 
  the 
  teeth 
  of 
  the 
  present 
  species, 
  

   and 
  the 
  T. 
  sicaria 
  C. 
  Fig. 
  A 
  represesents 
  the 
  former 
  and 
  fig. 
  B 
  the 
  latter. 
  

  

  The 
  peculiar 
  form 
  of 
  the 
  tooth 
  on 
  which 
  T 
  . 
  contusor 
  was 
  based, 
  is 
  due 
  I 
  find 
  to 
  attrition 
  

   and 
  partial 
  destruction 
  of 
  the 
  enamel. 
  

   B 
  A 
  " 
  Eocene 
  " 
  of 
  Eastern 
  Virginia 
  from 
  the 
  banks 
  of 
  the 
  Potomac. 
  

  

  THECACHAMPSA 
  SERICODON, 
  Cope. 
  

   Proceed. 
  Acad. 
  Nat. 
  Sci., 
  Philad., 
  1867, 
  p. 
  143. 
  

  

  This 
  species 
  was 
  established 
  on 
  fragments 
  of 
  three 
  teeth 
  from 
  the 
  Miocene 
  of 
  Maryland. 
  Four 
  additional 
  and 
  

   much 
  more 
  perfect 
  teeth, 
  with 
  fragments 
  of 
  jaws, 
  from 
  New 
  Jersey, 
  presented 
  by 
  my 
  friend, 
  Dr. 
  II. 
  0. 
  Wood, 
  Jr., 
  

   elucidate 
  the 
  characters 
  of 
  both 
  species 
  and 
  genus. 
  

  

  In. 
  

  

  Lin. 
  

  

  8 
  

  

  4. 
  

  

  

  11. 
  

  

  1 
  

  

  4. 
  

  

  2 
  

  

  8. 
  

  

  3 
  

  

  3. 
  

  

  

  8. 
  

  

  2 
  

  

  8. 
  

  

  69 
  

  

  5. 
  

  

  4 
  

  

  

  3 
  

  

  10.5 
  

  

  2 
  

  

  3.5 
  

  

  2 
  

  

  0.8 
  

  

  