﻿A 
  PLESIOSAURIAN 
  FROM 
  THE 
  OXFORD 
  CLAY. 
  205 
  

  

  the 
  centrum 
  as 
  in 
  the 
  cervical 
  region 
  ; 
  and 
  the 
  upper 
  part 
  of 
  the 
  

   centrum 
  is 
  but 
  slightly 
  compressed 
  laterally, 
  so 
  that 
  the 
  sides 
  of 
  the 
  

   bone 
  are 
  not 
  very 
  concave 
  from 
  back 
  to 
  front. 
  The 
  pedicles 
  to 
  

   which 
  the 
  chevron 
  bones 
  were 
  attached 
  have 
  left 
  rough 
  granulated 
  

   surfaces, 
  which 
  do 
  not 
  enter 
  into 
  the 
  posterior 
  face 
  of 
  the 
  centrum 
  ; 
  

   they 
  look 
  obliquely 
  downward 
  and 
  backward 
  ; 
  and 
  often 
  one 
  is 
  some- 
  

   what 
  larger 
  than 
  the 
  other 
  ; 
  and 
  occasionally 
  the 
  chevron 
  bones 
  were 
  

   anchylosed 
  to 
  them*. 
  

  

  The 
  Coracoids. 
  

  

  The 
  extreme 
  width 
  of 
  the 
  coracoids 
  from 
  side 
  to 
  side 
  immediately 
  

   behind 
  the 
  articulations 
  is 
  rather 
  less 
  than 
  14 
  inches. 
  The 
  bones 
  are 
  

   imperfectly 
  preserved, 
  the 
  whole 
  of 
  their 
  interior 
  and 
  posterior 
  parts 
  

   being 
  broken 
  away 
  ; 
  moreover 
  they 
  are 
  crushed 
  at 
  the 
  articular 
  sur- 
  

   faces, 
  except 
  in 
  the 
  median 
  line. 
  As 
  much 
  as 
  is 
  preserved 
  of 
  the 
  me- 
  

   dian 
  suture 
  measures 
  4 
  inches 
  in 
  length 
  and 
  2 
  inches 
  in 
  depth 
  ; 
  the 
  

   surface 
  is 
  pyriform, 
  tapering 
  most 
  rapidly 
  behind. 
  The 
  two 
  bones 
  ap- 
  

   pear 
  to 
  have 
  been 
  placed 
  during 
  life 
  very 
  nearly 
  in 
  the 
  same 
  plane. 
  The 
  

   abdominal 
  surface 
  behind 
  the 
  broad 
  thick 
  anterior 
  part 
  and 
  within 
  

   the 
  curved 
  lateral 
  parts 
  was 
  a 
  shallow 
  basin 
  ; 
  and 
  externally 
  the 
  

   bones 
  presented 
  a 
  corresponding 
  bulging, 
  which 
  in 
  the 
  median 
  line 
  

   of 
  the 
  body 
  formed 
  a 
  marked 
  keel 
  ; 
  externally, 
  at 
  right 
  angles 
  to 
  

   this 
  keel, 
  where 
  thickest, 
  the 
  bone 
  is 
  compressed 
  and 
  extends 
  trans- 
  

   versely 
  as 
  a 
  rounded 
  surface 
  towards 
  the 
  point 
  where 
  the 
  articular 
  

   surfaces 
  for 
  the 
  scapula 
  and 
  humerus 
  meet, 
  but 
  does 
  not 
  reach 
  

   them. 
  The 
  whole 
  of 
  the 
  articular 
  surface 
  for 
  the 
  scapula 
  lies 
  in 
  

   front 
  of 
  this 
  rounded 
  ridge, 
  which 
  has 
  a 
  concave 
  outline 
  in 
  front 
  on 
  

   each 
  side, 
  with 
  the 
  concavities 
  approximating 
  anteriorly 
  so 
  as 
  to 
  

   form 
  a 
  strong 
  median 
  process, 
  which 
  extends 
  further 
  forward 
  than 
  

   any 
  part 
  of 
  the 
  articular 
  surface 
  for 
  the 
  scapula. 
  In 
  front 
  of 
  this 
  

   rounded 
  transverse 
  ridge 
  the 
  inner 
  side 
  of 
  the 
  bone 
  is 
  prolonged 
  

   anteriorly, 
  so 
  as 
  to 
  form 
  a 
  compressed 
  anterior 
  extension 
  of 
  the 
  

   coracoid, 
  very 
  thin 
  and 
  deeply 
  concave 
  in 
  its 
  antero-posterior 
  ex- 
  

   tension 
  of 
  nearly 
  an 
  inch, 
  and 
  very 
  slightly 
  concave 
  from 
  side 
  to 
  

   side. 
  It 
  is 
  broken 
  away 
  towards 
  the 
  median 
  line 
  of 
  the 
  animal 
  ; 
  but 
  

   towards 
  the 
  outer 
  anterior 
  surface 
  it 
  widens 
  and 
  thickens, 
  blending 
  

   with 
  the 
  adjacent 
  bone 
  to 
  support 
  the 
  articulation 
  for 
  the 
  scapula. 
  

   The 
  length 
  of 
  the 
  scapula-articulation 
  is 
  rather 
  over 
  2k 
  inches 
  ; 
  it 
  

   looks 
  obliquely 
  forward 
  and 
  outward. 
  In 
  its 
  compressed 
  state 
  it 
  is 
  

   1| 
  inch 
  deep 
  where 
  it 
  joins 
  the 
  articular 
  surface 
  for 
  the 
  humerus, 
  

   which 
  is 
  about 
  equally 
  long 
  and 
  concave 
  from 
  before 
  backward, 
  and 
  

   from 
  below 
  upward 
  ; 
  its 
  anterior 
  margin 
  is 
  6 
  inches, 
  and 
  its 
  

   posterior 
  margin 
  7| 
  inches 
  from 
  the 
  median 
  line. 
  The 
  least 
  

   width 
  across 
  both 
  the 
  coracoids 
  from 
  side 
  to 
  side 
  is 
  9| 
  inches 
  at 
  a 
  

   distance 
  of 
  7 
  inches 
  behind 
  the 
  anterior 
  apex 
  of 
  the 
  bones 
  ; 
  the 
  

   extreme 
  posterior 
  extension 
  is 
  13| 
  inches 
  behind 
  the 
  most 
  anterior 
  

  

  * 
  I 
  have 
  occasionally 
  seen 
  similar 
  caudal 
  vertebras 
  from 
  the 
  Kimmeridge 
  

   Clay 
  ; 
  and 
  about 
  five 
  years 
  ago 
  Mr. 
  Charlesworth 
  showed 
  me 
  a 
  series 
  of 
  cervical, 
  

   dorsal, 
  and 
  caudal 
  vertebrae 
  from 
  the 
  Kimmeridge 
  Clay 
  of 
  Ely, 
  with 
  the 
  caudals 
  

   eimilar 
  ; 
  but 
  they 
  belonged 
  to 
  a 
  distinct 
  species. 
  

  

  