﻿OF 
  THE 
  PLESIOSAt'EIA^ 
  PECTOEAX 
  ABCH. 
  

  

  447 
  

  

  scapula. 
  The 
  anterior 
  and 
  inner 
  margin 
  of 
  the 
  scapula 
  similarly 
  

   terminates 
  in 
  an 
  edge 
  which 
  gave 
  attachment 
  to 
  cartilage, 
  showing, 
  

   I 
  think, 
  that 
  the 
  anterior 
  median 
  portion 
  of 
  the 
  pectoral 
  arch 
  was 
  

   occupied 
  not 
  by 
  an 
  interelaviele, 
  but 
  by 
  a 
  common 
  cartilage, 
  at 
  the 
  

   expense 
  of 
  which 
  the 
  scapular 
  ossifications 
  extended 
  till 
  they 
  met 
  in 
  

   the 
  median 
  line. 
  

  

  The 
  scapula 
  is 
  remarkable 
  chiefly 
  for 
  the 
  length 
  of 
  the 
  acromial 
  

   process 
  (which 
  is 
  directed 
  outward), 
  for 
  the 
  straight 
  antero-lateral 
  

   margin 
  which 
  the 
  bone 
  thus 
  obtains, 
  for 
  the 
  expansion 
  of 
  its 
  ante- 
  

   rior 
  end, 
  and 
  for 
  the 
  small 
  foramen 
  which 
  it 
  combines 
  with 
  the 
  

   coracoid 
  to 
  enclose. 
  

  

  These 
  characters 
  are 
  supported 
  by 
  others 
  in 
  all 
  parts 
  of 
  the 
  

   skeleton 
  : 
  thus 
  the 
  pubic 
  bones 
  have 
  a 
  prepubic 
  process 
  directed 
  

   anteriorly, 
  like 
  that 
  seen 
  in 
  Chelonians 
  ; 
  and 
  Prof. 
  Owen 
  describes 
  

   and 
  figures 
  distinct 
  olecranon 
  and 
  patella 
  bones. 
  The 
  caudal 
  ver- 
  

   tebra; 
  give 
  no 
  indication 
  of 
  chevron 
  bones. 
  

  

  CoiTMBOSAUBTTS, 
  g. 
  n. 
  (Tig. 
  12.) 
  

  

  The 
  coracoid 
  bones 
  are 
  oblong, 
  widening 
  at 
  the 
  posterior 
  angles, 
  

   and 
  not 
  extending 
  anterior 
  to 
  the 
  humeral 
  articulation, 
  except 
  

  

  Fig. 
  12. 
  — 
  Pectoral 
  Arch 
  o/Colymbosaurus, 
  from 
  a 
  Specimen 
  In 
  the 
  

   Museum 
  at 
  Ely. 
  

  

  s. 
  Scapula. 
  

  

  c. 
  Coracoid. 
  

  

  g. 
  Glenoid 
  carity. 
  

  

  slightly 
  in 
  the 
  median 
  line 
  of 
  the 
  body, 
  and 
  not 
  cupped 
  deeply 
  to 
  

   form 
  the 
  foramen 
  between 
  the 
  scapula 
  and 
  coracoid. 
  

  

  The 
  scapula 
  is 
  of 
  extraordinary 
  form 
  ; 
  the 
  two 
  bones 
  meet 
  in 
  the 
  

   median 
  fine 
  of 
  the 
  body, 
  meet 
  tbe 
  coracoids 
  behind 
  by 
  a 
  narrow 
  

   union, 
  and 
  enclose 
  the 
  greater 
  part 
  of 
  a 
  large 
  foramen 
  ; 
  the 
  ante- 
  

   rior 
  margins 
  of 
  the 
  bones 
  are 
  straight, 
  converge 
  at 
  about 
  an 
  angle 
  

   of 
  90° 
  ; 
  the 
  posterior 
  end 
  of 
  the 
  straight 
  side 
  is 
  prolonged 
  into 
  a 
  

   blunt 
  process, 
  between 
  which 
  and 
  the 
  humeral 
  articulation 
  the 
  side 
  

   of 
  the 
  bone 
  is 
  concave. 
  

  

  These 
  Plesiosaurians 
  all 
  have 
  very 
  long 
  slender 
  necks, 
  and 
  closely 
  

   approximate 
  to 
  the 
  Elasmosaurus 
  of 
  Cope, 
  with 
  which 
  I 
  hesitate 
  to 
  

   identify 
  it 
  till 
  we 
  know 
  more 
  details 
  of 
  the 
  structure 
  of 
  the 
  Ame- 
  

  

  