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  H. 
  G. 
  SEELET 
  ON 
  A 
  DINOSAURIAN 
  CORACOID. 
  

  

  the 
  external 
  articular 
  margin 
  of 
  the 
  bone 
  is 
  straight 
  ; 
  the 
  concave 
  

   posterior 
  margin 
  is 
  rounded 
  from 
  below 
  upward, 
  and 
  maintains 
  a 
  

   uniform 
  thickness 
  of 
  about 
  2\ 
  centim. 
  (1 
  in.). 
  

  

  The 
  external 
  margin 
  (fig. 
  4) 
  consists 
  of 
  two 
  parts 
  : 
  — 
  a 
  posterior 
  

   semiovate 
  articulation, 
  a 
  ; 
  and 
  an 
  anterior 
  subtriangular 
  sutural 
  sur- 
  

   face 
  for 
  the 
  scapula, 
  b. 
  The 
  latter 
  is 
  about 
  15 
  centim. 
  (6 
  in.) 
  thick, 
  

   and 
  measures 
  about 
  17 
  centim. 
  (6| 
  in.) 
  on 
  the 
  line 
  where 
  it 
  meets 
  

   the 
  glenoid 
  cavity. 
  The 
  external 
  margin 
  is 
  about 
  17 
  centim. 
  

   (6| 
  in.) 
  long, 
  and 
  the 
  internal 
  margin 
  is 
  about 
  27 
  centim. 
  (10| 
  

   in.) 
  long. 
  Where 
  it 
  terminates 
  anteriorly 
  the 
  bone 
  is 
  about 
  4 
  centim. 
  

   {Yj; 
  in.) 
  thick. 
  The 
  sutural 
  surface 
  is 
  irregular 
  and 
  undulating, 
  but 
  

   lies 
  essentially 
  in 
  one 
  plane 
  ; 
  it 
  is 
  rough 
  with 
  cartilaginous 
  attach- 
  

   ment. 
  It 
  is 
  at 
  a 
  right 
  angle 
  with 
  the 
  interior 
  margin 
  of 
  the 
  bone, 
  

   but 
  makes 
  a 
  sharp 
  angle 
  with 
  the 
  external 
  surface. 
  

  

  Fig. 
  4. 
  — 
  Scapulo-ylenoid 
  Surface 
  of 
  Dinosaurian 
  Coracoid. 
  

  

  a. 
  Glenoid 
  cavity 
  of 
  humerus. 
  b. 
  Sutural 
  surface 
  for 
  scapula. 
  

  

  The 
  articular 
  surface 
  for 
  the 
  humerus 
  has 
  its 
  outline 
  convex 
  ex- 
  

   ternally 
  (fig. 
  4) 
  ; 
  behind 
  the 
  convexity 
  it 
  is 
  sharper 
  ; 
  and 
  internally 
  it 
  

   is 
  straight. 
  The 
  greatest 
  thickness 
  of 
  the 
  bone 
  is 
  a 
  little 
  over 
  17 
  

   centim. 
  (6| 
  in.), 
  the 
  greatest 
  length 
  of 
  the 
  surface 
  is 
  18 
  centim. 
  

   (7j~ 
  in.), 
  and 
  its 
  greatest 
  width 
  about 
  10 
  centim. 
  (4 
  in.) 
  ; 
  the 
  glenoid 
  

   cavity 
  is 
  gently 
  concave, 
  but 
  towards 
  the 
  outer 
  part 
  shows 
  grooves 
  

   which 
  indicate 
  that 
  the 
  articular 
  cartilage 
  was 
  not 
  entirely 
  ossified. 
  

  

  Of 
  all 
  coracoids 
  of 
  British 
  Dinosaurs, 
  that 
  which 
  approaches 
  

   nearest 
  to 
  this 
  type 
  is 
  seen 
  in 
  the 
  skeleton 
  referred 
  to 
  Hylceosaurus 
  

   from 
  the 
  Wealden 
  of 
  Tilgate. 
  But 
  in 
  Hylceosaurus 
  the 
  distal 
  por- 
  

   tion 
  of 
  the 
  bone 
  is 
  more 
  prolonged, 
  the 
  median 
  portion 
  is 
  less 
  

   thickened, 
  and 
  the 
  foramen 
  is 
  placed 
  behind 
  the 
  middle 
  of 
  the 
  

   humeral 
  border 
  far 
  away 
  from 
  the 
  scapular 
  margin. 
  The 
  bone 
  is 
  

  

  