﻿62 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  No 
  facial 
  foramen 
  ; 
  muzzle 
  long 
  slender. 
  

  

  HOLOPS. 
  

  

  aa 
  The 
  cervical 
  vertebrae 
  with 
  long 
  simple 
  zygapophyses. 
  

   Muzzle 
  long 
  narrow, 
  with 
  long 
  symphysis 
  ; 
  teeth 
  very 
  unequal. 
  

  

  THECACHAMPSA. 
  

  

  Muzzle 
  broad 
  short, 
  symphysis 
  short. 
  

  

  PLERODON. 
  

  

  AA 
  Teeth 
  crowns 
  a 
  single 
  dentinal 
  cone 
  with 
  enamel 
  sheath. 
  

   Cervical 
  hypapophyses 
  rudimental 
  ; 
  muzzle 
  broad. 
  

  

  BOTTOSAURUS* 
  

  

  Cervical 
  hypapophyses 
  elongate, 
  simple. 
  

  

  EXISTING 
  CROCODILIA. 
  

  

  Species 
  of 
  this 
  order 
  have 
  been 
  abundant 
  in 
  North 
  America 
  from 
  the 
  beginning 
  of 
  the 
  

   Cretaceous 
  period 
  to 
  the 
  end 
  of 
  the 
  Miocene. 
  At 
  present 
  they 
  are 
  confined 
  to 
  its 
  extreme 
  

   southern 
  regions. 
  

  

  The 
  Cretaceous 
  period 
  was 
  more 
  prolific 
  in 
  them 
  than 
  any 
  later 
  one, 
  for 
  then 
  the 
  

   Reptilian 
  type 
  in 
  all 
  its 
  representatives 
  reached 
  its 
  fullest 
  development 
  in 
  the 
  numbers, 
  

   variety 
  and 
  size 
  of 
  its 
  members. 
  Then 
  our 
  sea 
  coasts, 
  estuaries, 
  and 
  fresh 
  waters 
  

   swarmed 
  with 
  them, 
  an 
  indication 
  of 
  the 
  prolific 
  lesser 
  life 
  on 
  which 
  they 
  preyed 
  or 
  

   otherwise 
  vented 
  their 
  powers 
  of 
  destruction. 
  

  

  THECACHAMPSA, 
  Cope. 
  

   Proceedings 
  Academy 
  Natural 
  Sciences, 
  1867, 
  p. 
  143. 
  

  

  This 
  genus 
  was 
  characterized 
  from 
  a 
  few 
  teeth 
  from 
  the 
  Miocene 
  of 
  Maryland. 
  

   Since 
  then 
  additional 
  material 
  has 
  enabled 
  me 
  to 
  construct 
  its 
  characters 
  more 
  fully. 
  

  

  Muzzle 
  elongate, 
  slender, 
  as 
  in 
  Gavialis, 
  the 
  symphysis 
  of 
  the 
  mandible 
  elongate 
  ; 
  den- 
  

   tal 
  series 
  interrupted 
  by 
  larger 
  canine-like 
  teeth. 
  Dentine 
  of 
  the 
  crown 
  arranged 
  in 
  

   concentric 
  cones. 
  Enamel 
  thin, 
  with 
  a 
  delicate 
  anterior 
  and 
  posterior 
  cutting 
  ridge 
  near 
  

   the 
  tip 
  of 
  the 
  crown. 
  Cervical 
  hypapophyses 
  elongate, 
  simple. 
  

  

  The 
  concentric 
  structure 
  of 
  the 
  dentine 
  in 
  this 
  genus 
  is 
  quite 
  the 
  same 
  as 
  in 
  Thora- 
  

   cosaurus. 
  I 
  do 
  not 
  discover 
  in 
  it 
  sections 
  of 
  the 
  teeth 
  of 
  Gavialis, 
  Mecistops 
  and 
  Croco- 
  

   dilus. 
  The 
  cones 
  readily 
  separate 
  and 
  fall 
  out 
  in 
  the 
  fossil 
  specimens. 
  Their 
  existence 
  

   would 
  indicate 
  a 
  periodical 
  cessation 
  of 
  activity 
  in 
  the 
  secretory 
  vessels 
  on 
  the 
  wall 
  of 
  the 
  

   pulp 
  cavity 
  of 
  the 
  teeth, 
  with 
  intervening 
  increase 
  of 
  deposit 
  of 
  dentine. 
  In 
  a 
  shed 
  tooth 
  

   of 
  this 
  genus 
  four 
  such 
  cones 
  may 
  be 
  counted. 
  f 
  

  

  *Probably 
  the 
  thin 
  crown 
  in 
  this 
  genus 
  is 
  composed 
  of 
  several 
  attenuated 
  cones. 
  

  

  \A 
  supposed 
  affinity 
  of 
  this 
  genus 
  to 
  Mosasaurus, 
  which 
  I 
  inserted 
  in 
  the 
  original 
  description, 
  at 
  the 
  suggestion 
  of 
  

   a 
  friend, 
  I 
  do 
  not 
  now 
  recognize. 
  

  

  