﻿114 
  THE 
  EXTINCT 
  BATRACHIA, 
  REPTILIA 
  

  

  familiar 
  to 
  all 
  since 
  the 
  publication 
  by 
  Hitchcock 
  and 
  Deane 
  of 
  the 
  histories 
  of 
  the 
  great 
  

   foot 
  tracks 
  of 
  the 
  Triassic 
  Red 
  Sandstone 
  of 
  the 
  Connecticut 
  Valley. 
  Such 
  tracks 
  have 
  

   been 
  discovered 
  by 
  John 
  Srnock 
  in 
  the 
  same 
  formation 
  in 
  New 
  Jersey, 
  and 
  by 
  Dr. 
  Chas. 
  

   Hitchcock 
  in 
  Pennsylvania. 
  Prof. 
  Hitchcock 
  ascribed 
  the 
  tracks 
  described 
  by 
  him 
  to 
  

   birds. 
  Prof. 
  Agassiz* 
  expresses 
  the 
  belief 
  that 
  they 
  were 
  made 
  by 
  vertebrates 
  combining 
  

   characters 
  of 
  existing 
  classes, 
  perhaps 
  of 
  Reptiles 
  and 
  Mammals, 
  rather 
  than 
  by 
  birds. 
  

   Now 
  a 
  carnivorous 
  Dinosaur 
  probably 
  allied 
  to 
  Laelaps, 
  as 
  proven 
  by 
  a 
  portion 
  of 
  the 
  jaw 
  

   with 
  teeth, 
  in 
  the 
  Academy's 
  Museum, 
  the 
  Bathygnathus 
  borealis 
  of 
  Leidy, 
  has 
  left 
  its 
  re- 
  

   mains 
  in 
  the 
  red 
  sandstone 
  of 
  Prince 
  Edward's 
  Island, 
  of 
  the 
  same 
  age, 
  and 
  we 
  safely 
  con- 
  

   clude 
  that 
  some 
  of 
  the 
  large 
  clawed 
  biped 
  tracks 
  of 
  Hitchcock 
  resemble 
  those 
  of 
  that 
  animal. 
  

   Dr. 
  Leidy 
  has 
  suspected 
  that 
  this 
  would 
  prove 
  to 
  be 
  the 
  case, 
  as 
  he 
  asksf 
  " 
  was 
  this 
  

   animal 
  probably 
  not 
  one 
  of 
  the 
  bipeds 
  which 
  made 
  the 
  so-called 
  tracks 
  in 
  the 
  sandstone 
  

   of 
  the 
  Connecticut 
  Valley 
  V 
  This 
  inquiry 
  was 
  after 
  an 
  examination 
  of 
  the 
  form 
  of 
  Laelaps, 
  

   answered 
  in 
  the 
  affirmative. 
  I 
  have 
  ascribed 
  these 
  tracks 
  to 
  Reptiles 
  allied 
  to 
  Laelaps,J 
  

   and 
  Huxley 
  believes 
  also 
  that 
  they 
  were 
  made 
  by 
  Dinosauria.§ 
  

  

  The 
  creatures 
  which 
  strode 
  along 
  the 
  flats 
  of 
  the 
  Triassic 
  estuary 
  have 
  been 
  various 
  in 
  

   species 
  and 
  genera, 
  as 
  pointed 
  out 
  by 
  Hitchcock. 
  Some 
  were 
  purely 
  biped 
  ; 
  some 
  occa- 
  

   sionally 
  supported 
  themselves 
  on 
  a 
  pair 
  of 
  reduced 
  fore 
  limbs. 
  There 
  are 
  impressions 
  

   where 
  these 
  creatures 
  have 
  squatted 
  on 
  their 
  haunches. 
  One 
  can 
  well 
  imagine 
  the 
  singu- 
  

   lar 
  effect 
  which 
  these 
  huge 
  gregarious 
  reptiles 
  would 
  "produce 
  standing 
  motionless, 
  or 
  

   marching 
  or 
  wading 
  slowly 
  along 
  the 
  water's 
  edge, 
  ready 
  for 
  a 
  plunge 
  at 
  passing 
  fishes 
  or 
  

   swimming 
  reptiles. 
  But 
  in 
  the 
  active 
  pursuit 
  of 
  terrestrial 
  prey 
  did 
  such 
  an 
  animal 
  as 
  the 
  

   Laelaps 
  run 
  like 
  the 
  Ostrich, 
  or 
  leap 
  like 
  the 
  Kangaroo. 
  So 
  far 
  as 
  the 
  triassic 
  tracks 
  go, 
  

   there 
  is 
  little 
  evidence 
  of 
  leapers, 
  chiefly 
  runners, 
  fell 
  upon 
  an 
  exhausted 
  quarry. 
  Or 
  

   Avere 
  they 
  only 
  carrion 
  eaters, 
  tearing 
  and 
  devouring 
  the 
  dead 
  of 
  age 
  and 
  disease 
  ? 
  Probably 
  

   some 
  were 
  such, 
  but 
  the 
  prehensile 
  claws 
  of 
  Laelaps 
  are 
  like 
  instruments 
  for 
  hoi 
  ding- 
  

   living 
  prey. 
  

  

  Laelaps 
  has 
  a 
  long 
  femur 
  ; 
  those 
  great 
  leapers 
  the 
  Kangaroos 
  have 
  a 
  short 
  one 
  ; 
  the 
  

   cursorial 
  birds, 
  however, 
  have 
  a 
  similarly 
  short 
  femur, 
  but 
  they 
  do 
  not 
  leap. 
  So 
  this 
  form 
  

   is 
  not 
  conclusive. 
  The 
  modern 
  Iguanas 
  have 
  a 
  long 
  femur, 
  and 
  they 
  all 
  progress 
  by 
  their 
  

   simultaneous 
  motion 
  ; 
  they 
  only 
  leap 
  ; 
  but 
  man 
  with 
  his 
  long 
  femur 
  runs 
  only. 
  The 
  

   question, 
  then, 
  does 
  not 
  depend 
  on 
  the 
  form 
  of 
  the 
  femur. 
  

  

  I 
  have 
  suggested, 
  on 
  a 
  former 
  occasion, 
  that 
  Laelaps 
  took 
  enormous 
  leaps, 
  and 
  struck 
  

   its 
  prey 
  with 
  its 
  hind 
  limbs. 
  1 
  say, 
  in 
  describing 
  it, 
  " 
  the 
  small 
  size 
  of 
  the 
  fore 
  limbs 
  

  

  * 
  Contrib. 
  Nat. 
  Hist. 
  U. 
  S., 
  1857, 
  Vol. 
  I. 
  f 
  J° 
  ur 
  - 
  Ac 
  - 
  Nat 
  - 
  Sciences, 
  1854, 
  323. 
  

  

  \ 
  American 
  Naturalist, 
  1807, 
  27. 
  Hays' 
  Medical 
  News 
  and 
  Reporter, 
  18G8. 
  

   § 
  Proceedings 
  Royal 
  Society, 
  London, 
  1868. 
  Natural 
  Science 
  Review, 
  18C8. 
  

  

  