﻿AND 
  AVES 
  OF 
  NORTH 
  AMERICA. 
  Ill 
  

  

  the 
  body, 
  as 
  the 
  animal 
  was 
  furnished 
  with 
  a 
  tail 
  of 
  greater 
  or 
  less 
  weight. 
  This 
  member 
  

   bears 
  however 
  little 
  proportion 
  to 
  the 
  great 
  size 
  of 
  those 
  seen 
  in 
  Iguanodon, 
  Hadrosaurus, 
  

   etc.., 
  but 
  exhibits 
  a 
  commencement 
  of 
  the 
  reduction 
  which 
  is 
  so 
  striking 
  among 
  the 
  birds. 
  

  

  The 
  proportions 
  of 
  the 
  metatarsus 
  are 
  only 
  to 
  be 
  ascertained 
  by 
  an 
  examination 
  of 
  those 
  

   of 
  allied 
  species, 
  as 
  L. 
  macropus 
  and 
  Megalosaurus 
  bucklandii. 
  As 
  all 
  the 
  other 
  bones 
  

   are 
  more 
  slender 
  than 
  those 
  of 
  the 
  latter, 
  so 
  were 
  no 
  doubt 
  these 
  bones 
  longer 
  in 
  propor- 
  

   tion 
  to 
  their 
  breadth. 
  I 
  have 
  estimated 
  it 
  above, 
  as 
  equal 
  to 
  a 
  little 
  over 
  half 
  the 
  tibia. 
  

  

  The 
  digits 
  in 
  the 
  genus 
  Laelaps 
  have 
  not 
  in 
  all 
  probability, 
  been 
  more 
  than 
  three. 
  

   The 
  less 
  bird-like 
  forms 
  of 
  Hylaeosaurus 
  and 
  Iguanodon, 
  have 
  had 
  according 
  to 
  Owen, 
  but 
  

   three 
  metatarsals, 
  and 
  it 
  is 
  not 
  according 
  to 
  the 
  rule 
  of 
  successional 
  relation, 
  that 
  there 
  

   should 
  be 
  any 
  repetition 
  of 
  a 
  reptilian 
  character, 
  in 
  a 
  point 
  of 
  prime 
  importance 
  in 
  mea- 
  

   suring 
  the 
  steps 
  of 
  succession 
  between 
  reptiles 
  and 
  birds. 
  Laelaps 
  and 
  probably 
  Megalo- 
  

   saurus, 
  also, 
  had 
  but 
  three 
  digits 
  directed 
  anteriorly, 
  and 
  a 
  fourth 
  rudimental. 
  

  

  It 
  is 
  true 
  that 
  Deslongchamps 
  ascribes 
  five 
  digits 
  to 
  Poecilopleurum 
  after 
  a 
  careful 
  

   study 
  of 
  abundant 
  material. 
  He 
  was 
  however 
  much 
  more 
  impressed 
  with 
  the 
  crocodilian 
  

   affinities 
  of 
  that 
  reptile 
  than 
  with 
  any 
  other, 
  and 
  did 
  not 
  recognize 
  the 
  avine 
  in 
  the 
  astra- 
  

   galus. 
  It 
  seems 
  to 
  me 
  quite 
  possible 
  that 
  one 
  of 
  his 
  toes 
  can 
  be 
  dispensed 
  with, 
  for 
  exam- 
  

   ple 
  the 
  second, 
  of 
  which 
  but 
  one 
  phalange 
  is 
  said 
  to 
  remain. 
  If 
  we 
  ascribe 
  the 
  fractured 
  

   extremity 
  of 
  the 
  bone 
  regarded 
  (Tab. 
  VIII., 
  p. 
  6,) 
  as 
  the 
  first 
  phalange 
  of 
  the 
  fourth 
  digit, 
  

   to 
  the 
  metatarsal 
  of 
  the 
  same, 
  the 
  phalange 
  referred 
  to 
  the 
  second 
  may 
  find 
  another 
  place. 
  

   The 
  fifth 
  digit 
  also 
  rests 
  on 
  the 
  evidence 
  of 
  one 
  phalange 
  only. 
  Though 
  the 
  reasoning 
  of 
  

   Deslongchamps 
  in 
  referring 
  these 
  pieces 
  is 
  good, 
  it 
  seems 
  to 
  me 
  that 
  renewed 
  study 
  might 
  

   result 
  in 
  ascribing 
  to 
  his 
  genus, 
  three 
  toes 
  anteriorly 
  and 
  one 
  appendicular, 
  his 
  first. 
  

  

  The 
  predominance 
  of 
  reptilian 
  characters 
  in 
  the 
  Dinosauria 
  as 
  indicated 
  by 
  the 
  struc- 
  

   ture 
  of 
  the 
  vertebrae, 
  and 
  other 
  points, 
  renders 
  it 
  probable 
  that 
  the 
  vertebral 
  column 
  did 
  

   not 
  present 
  that 
  remarkable 
  flexure 
  where 
  the 
  cervical 
  and 
  dorsal 
  series 
  are 
  joined, 
  which 
  

   is 
  seen 
  in 
  the 
  birds, 
  but 
  rather 
  that 
  they 
  were 
  more 
  or 
  less 
  continuous, 
  and 
  formed 
  a 
  con- 
  

   tinuum 
  from 
  the 
  sacrum 
  to 
  the 
  nape. 
  The 
  cervicals 
  may 
  have 
  been 
  somewhat 
  elongated 
  

   as 
  in 
  some 
  birds, 
  yet 
  this 
  is 
  not 
  probable 
  in 
  view 
  of 
  the 
  necessary 
  balance 
  to 
  be 
  preserved, 
  

   which 
  would 
  not 
  admit 
  of 
  much 
  projection 
  of 
  the 
  cranium 
  anteriorly. 
  The 
  cervicals 
  of 
  

   Hadrosaurus 
  are 
  not 
  so 
  long 
  as 
  in 
  the 
  modern 
  Varani 
  ; 
  in 
  Iguanodon 
  they 
  are 
  similar, 
  while 
  

   their 
  rather 
  oblique 
  articular 
  faces 
  indicate 
  the 
  elevation 
  of 
  that 
  region, 
  and 
  of 
  the 
  position 
  

   of 
  the 
  cranium. 
  In 
  the 
  case 
  of 
  these 
  animals, 
  there 
  is 
  not 
  the 
  same 
  necessity 
  for 
  a 
  long- 
  

   neck 
  as 
  in 
  the 
  birds, 
  for 
  even 
  in 
  Laelaps 
  and 
  other 
  genera 
  which 
  probably 
  never 
  used 
  the 
  

   fore 
  limbs 
  in 
  progression, 
  they 
  furnished 
  a 
  support 
  to 
  the 
  body 
  when 
  the 
  head 
  was 
  em- 
  

   ployed 
  in 
  taking 
  food, 
  etc., 
  in 
  the 
  ground. 
  

  

  The 
  caudal 
  region 
  affects 
  the 
  general 
  proportions 
  of 
  a 
  vertebrated 
  animal 
  materially. 
  

  

  