﻿AND 
  AVES 
  OF 
  NORTH 
  AMERICA. 
  87 
  

  

  Iguanodon 
  and 
  Hadrosaurus 
  there 
  is 
  a 
  very 
  small 
  sphaeroid 
  condyle 
  on 
  the 
  inner 
  side 
  of 
  

   a 
  broad 
  proximal 
  extremity. 
  If 
  the 
  condyle 
  only 
  articulated 
  with 
  the 
  scapula, 
  the 
  rota- 
  

   tion 
  of 
  the 
  humerus 
  would 
  be 
  very 
  limited 
  ; 
  if 
  the 
  long 
  narrow 
  proximal 
  articular 
  surface, 
  

   which 
  is 
  the 
  whole 
  of 
  the 
  flattened 
  proximal 
  extremity 
  of 
  this 
  bone 
  the 
  rotation 
  would 
  be 
  

   still 
  less. 
  In 
  Laelaps 
  however 
  I 
  find 
  no 
  round 
  condyle, 
  only 
  the 
  long 
  narrow 
  articular 
  

   face 
  of 
  the 
  proximal 
  extremity, 
  as 
  in 
  the 
  Crocodiles. 
  This 
  would 
  not 
  allow 
  of 
  abduction 
  

   and 
  adduction, 
  but 
  as 
  in 
  the 
  bird, 
  of 
  only 
  flexure 
  and 
  extension. 
  This 
  is 
  readily 
  seen 
  in 
  

   the 
  movements 
  of 
  the 
  Crocodile. 
  I 
  suppose 
  the 
  anterior 
  limbs 
  were 
  more 
  useful 
  as 
  sup- 
  

   ports 
  when 
  these 
  animals 
  placed 
  the 
  head 
  near 
  the 
  ground, 
  than 
  for 
  any 
  other 
  purpose, 
  

   especially 
  in 
  Laelaps 
  and 
  its 
  allies. 
  

  

  The 
  character 
  of 
  the 
  articulation 
  of 
  the 
  vertebral 
  column 
  by 
  intervertebral 
  discs, 
  the 
  

   double 
  headed 
  ribs, 
  the 
  elongate 
  sacrum 
  and 
  large 
  medullary 
  cavities 
  of 
  the 
  long 
  bones 
  

   have 
  been 
  cited 
  by 
  Prof. 
  Owen 
  in 
  evidence 
  of 
  the 
  Mammalian 
  tendencies 
  of 
  the 
  animals 
  

   of 
  this 
  subclass. 
  Their 
  reptilian 
  features, 
  the 
  single 
  occipital 
  condyle, 
  quadrate 
  and 
  

   coracoid 
  bones, 
  with 
  the 
  median 
  tarsal 
  ginglymus, 
  are 
  equally 
  shared 
  by 
  the 
  Aves, 
  though 
  

   most 
  of 
  the 
  usual 
  distinctions 
  between 
  the 
  latter 
  class 
  and 
  the 
  Reptiles 
  hold 
  good 
  here 
  

   also. 
  Prof. 
  Owen 
  also 
  points 
  out 
  a 
  special 
  bird-like 
  tendency 
  in 
  the 
  alternation 
  instead 
  

   of 
  superposition 
  of 
  the 
  neural 
  arches 
  of 
  the 
  sacrum 
  on 
  their 
  centra 
  ; 
  and 
  other 
  points 
  can 
  

   can 
  now 
  be 
  added. 
  Thus 
  the 
  reduction 
  of 
  the 
  metatarsals 
  to 
  three 
  in 
  some 
  of 
  the 
  genera, 
  

   and 
  their 
  close 
  approximation 
  and 
  excess 
  of 
  length 
  over 
  the 
  phalanges, 
  brings 
  to 
  mind 
  

   these 
  bones 
  in 
  the 
  penguin. 
  With 
  the 
  same 
  reduction 
  follows 
  the 
  confluence 
  of 
  the 
  first 
  

   series 
  of 
  the 
  tarsal 
  bones, 
  and 
  the 
  great 
  diminution 
  of 
  strength 
  of 
  the 
  fibula 
  and 
  its 
  close 
  

   application 
  to 
  the 
  tibia 
  ; 
  the 
  front 
  limbs 
  are 
  much 
  reduced, 
  and 
  the 
  long 
  bones 
  more 
  pneu- 
  

   matic. 
  In 
  the 
  most 
  extreme 
  form 
  in 
  this 
  direction 
  known, 
  the 
  first 
  series 
  of 
  tarsal 
  bones 
  

   is 
  entirely 
  confluent 
  with 
  the 
  tibia 
  as 
  in 
  the 
  birds, 
  the 
  three 
  metatarsals 
  are 
  much 
  elon- 
  

   gate, 
  the 
  cervical 
  vertebrae 
  increase 
  in 
  number, 
  and 
  the 
  pubes 
  assume 
  a 
  position 
  at 
  right 
  

   angles 
  to 
  the 
  vertebral 
  axis, 
  which 
  is 
  intermediate 
  between 
  their 
  anterior 
  position 
  in 
  most 
  

   Reptiles, 
  and 
  their 
  posterior, 
  in 
  Birds. 
  

  

  These 
  features 
  indicate 
  three 
  perhaps 
  suborders, 
  which 
  are 
  defined 
  below. 
  

  

  Quite 
  as 
  important, 
  as 
  indicating 
  the 
  avine 
  affinity 
  and 
  remarkable 
  character 
  of 
  this 
  

   order, 
  is 
  the 
  evidence 
  derived 
  from 
  the 
  pelvis. 
  And 
  first, 
  the 
  support 
  of 
  this 
  arch, 
  the 
  

   femur, 
  has 
  been 
  already 
  alluded 
  to. 
  The 
  head 
  and 
  neck 
  of 
  this 
  bone 
  are 
  at 
  right 
  angles 
  

   to 
  the 
  direction 
  of 
  the 
  condyle. 
  In 
  other 
  reptiles 
  the 
  axes 
  of 
  these 
  are 
  oblique 
  to 
  each 
  

   other, 
  so 
  that 
  the 
  femur 
  does 
  not 
  move 
  in 
  the 
  direction 
  of 
  the 
  axis 
  of 
  the 
  body, 
  but 
  

   obliquely 
  to 
  it, 
  thus 
  permitting 
  the 
  body 
  to 
  rest 
  on 
  the 
  earth. 
  In 
  the 
  present 
  case 
  the 
  

   structure 
  is 
  the 
  same 
  as 
  in 
  the 
  birds 
  and 
  Mammals 
  ; 
  the 
  femur 
  could 
  only 
  move 
  in 
  a 
  plane 
  

   parallel 
  with 
  the 
  axis 
  of 
  the 
  body. 
  The 
  reduced 
  length 
  of 
  the 
  fore 
  limbs 
  of 
  many 
  Dino- 
  

  

  