﻿AND 
  AVES 
  OF 
  NORTH 
  AMERICA. 
  215 
  

  

  wardly 
  it 
  is 
  prolonged, 
  forming 
  the 
  lower 
  margin 
  of 
  the 
  internal 
  fossa, 
  and 
  then 
  passing 
  

   between 
  the 
  coronoid 
  and 
  articular. 
  A 
  third 
  laminar 
  prolongation 
  extends 
  to 
  beyond 
  

   even 
  these, 
  between 
  the 
  plates 
  of 
  the 
  splenial. 
  

  

  The 
  articular 
  is 
  the 
  largest 
  bone 
  behind 
  the 
  dentary. 
  It 
  is 
  convex 
  externally, 
  and 
  

   sends 
  a 
  longitudinal 
  ridge 
  from 
  the 
  cotyloid 
  cavity 
  to 
  that 
  of 
  the 
  coronoid, 
  thus 
  enclosing 
  

   a 
  large 
  shallow 
  fossa. 
  

  

  Fig. 
  50. 
  

  

  The 
  accompanying 
  cut 
  represent 
  a 
  section 
  of 
  the 
  ramus, 
  about 
  

   two 
  inches 
  behind 
  the 
  inferior 
  articulation 
  and 
  some 
  distance 
  be- 
  1 
  / 
  ^^» 
  l 
  

  

  hind 
  the 
  commencement 
  of 
  the 
  coronoid 
  process. 
  It 
  is 
  also 
  near 
  j||yf 
  

  

  the 
  distal 
  extremity 
  of 
  the 
  subarticular 
  and 
  the 
  proximal 
  of 
  the 
  l|Jl 
  

  

  1 
  splenial. 
  The 
  two 
  portions 
  of 
  the 
  angular 
  5 
  and 
  5' 
  unite 
  a 
  short 
  If 
  

  

  distance 
  anteriorly 
  beneath 
  the 
  1 
  splenial. 
  » 
  

  

  In 
  the 
  splenial 
  articulation 
  the 
  posterior 
  bone 
  presents 
  the 
  con- 
  &MI^3|111f 
  

  

  dyloid, 
  the 
  anterior 
  the 
  cotyloid 
  face. 
  The 
  former 
  narrows 
  and 
  re- 
  4 
  til^^^ 
  

   treats 
  upwards 
  and 
  backwards. 
  The 
  articulation 
  allows 
  of 
  a 
  ro- 
  1 
  coron 
  'd 
  

   tary 
  motion 
  inwards 
  and 
  upwards, 
  the 
  alveolar 
  margin 
  of 
  the 
  den- 
  3 
  Articulai 
  '- 
  

  

  , 
  i 
  1-^1 
  i 
  i.Li 
  mi- 
  . 
  ^ 
  Subarticular. 
  

  

  tary 
  bone 
  being 
  thrown 
  upwards 
  and 
  outwards. 
  I 
  his 
  motion 
  . 
  „ 
  

  

  J 
  ° 
  L 
  4 
  ? 
  Splenial. 
  

  

  is 
  permitted 
  by 
  the 
  laminar 
  character 
  of 
  the 
  overlapping 
  margins 
  5 
  and 
  5' 
  Angular, 
  

   of 
  the 
  splenial, 
  etc., 
  as 
  follows: 
  

  

  The 
  principal 
  body 
  of 
  the 
  dentary 
  comes 
  to 
  an 
  obtuse 
  but 
  grooved 
  posterior 
  termina- 
  

   tion. 
  Its 
  external 
  wall 
  is 
  prolonged 
  more 
  posteriorly, 
  the 
  inferior 
  margin 
  fittino- 
  a 
  rabbet 
  

   of 
  the 
  outside 
  of 
  the 
  splenial. 
  The 
  superior 
  margin 
  of 
  this 
  thin 
  plate 
  is 
  much 
  lower 
  than 
  

   the 
  truncate 
  extremity, 
  and 
  its 
  margin 
  gradually 
  rises 
  to 
  meet 
  the 
  outer 
  margin 
  of 
  the 
  latter. 
  

   The 
  section 
  of 
  the 
  splenial 
  is 
  U-shaped, 
  much 
  thickened 
  at 
  the 
  turn. 
  The 
  inner 
  lamina 
  is 
  

   more 
  elevated 
  than 
  the 
  outer, 
  and 
  is 
  concave, 
  turning 
  outwards 
  above 
  to 
  conform 
  to 
  the 
  

   dentary. 
  A 
  narrow 
  laminar 
  prolongation 
  of 
  the 
  angular 
  is 
  observed 
  between 
  the 
  folds 
  of 
  

   the 
  U. 
  An 
  outwardly 
  convex, 
  wedge-shaped 
  terminus 
  of 
  the 
  articular, 
  is 
  included 
  be- 
  

   tween 
  the 
  inner 
  lamina 
  of 
  the 
  coronoid 
  and 
  the 
  outer 
  lamina 
  of 
  the 
  dentary, 
  moving 
  

   freely 
  on 
  the 
  latter. 
  There 
  is, 
  then, 
  nothing 
  that 
  prevents 
  this 
  from 
  being 
  a 
  complete 
  

   articulation, 
  except 
  the 
  angular 
  lamina, 
  which 
  is 
  about 
  half 
  a 
  line 
  in 
  thickness, 
  and 
  proba- 
  

   bly 
  flexible 
  in 
  life. 
  

  

  The 
  superior 
  margin 
  of 
  the 
  coronoid 
  is 
  convex 
  outwardly, 
  and 
  is 
  not 
  continuous 
  with 
  

   that 
  of 
  the 
  dentary, 
  where 
  the 
  elements 
  forming 
  the 
  splenial 
  articulation 
  are 
  in 
  line. 
  

   When, 
  however, 
  the 
  process 
  of 
  the 
  articulation 
  is 
  properly 
  applied 
  to 
  the 
  dentary, 
  and 
  

   the 
  coronoid 
  and 
  splenial 
  are 
  in 
  line, 
  as 
  they 
  no 
  doubt 
  were 
  under 
  ordinary 
  circumstances 
  

   in 
  life, 
  the 
  curvature 
  of 
  the 
  upper 
  margin 
  of 
  the 
  ramus 
  is 
  continuous 
  and 
  normal. 
  At 
  

  

  