﻿A 
  PLESIOSAURIAN 
  FROM 
  THE 
  OXFORD 
  CLAY. 
  207 
  

  

  shape 
  is 
  probably 
  altered 
  by 
  compression. 
  The 
  external 
  surface 
  of 
  

   the 
  bone 
  is 
  slightly 
  convex 
  in 
  each 
  direction, 
  and 
  measures 
  7 
  inches 
  

   from 
  the 
  median 
  line 
  to 
  the 
  femoral 
  margin 
  ; 
  its 
  least 
  width 
  is 
  2| 
  

   inches 
  at 
  about 
  2 
  inches 
  from 
  the 
  femoral 
  surface. 
  The 
  anterior 
  

   margin 
  is 
  sharp 
  and 
  compressed 
  and 
  concave, 
  the 
  concavity 
  looking 
  

   forward 
  and 
  slightly 
  inward. 
  The 
  bone 
  appears 
  to 
  have 
  had 
  the 
  

   usual 
  triangular 
  form 
  seen 
  among 
  Plesiosaurs 
  ; 
  but 
  its 
  thin 
  posterior 
  

   expansion 
  is 
  not 
  entirely 
  preserved 
  ; 
  its 
  posterior 
  border 
  is 
  sharp 
  

   and 
  compressed, 
  thinner 
  than 
  the 
  anterior 
  border, 
  concave 
  in 
  a 
  curve 
  

   which 
  extends 
  inward 
  and 
  backward 
  to 
  within 
  about 
  2| 
  inches 
  of 
  

   the 
  median 
  line, 
  where 
  its 
  antero-posterior 
  extension 
  is 
  4| 
  inches 
  

   measured 
  from 
  border 
  to 
  border. 
  The 
  median 
  symphysis 
  is 
  thick 
  ; 
  

   rather 
  less 
  than 
  3 
  inches 
  of 
  it 
  is 
  preserved 
  antero-posteriorly 
  ; 
  and, 
  

   as 
  compressed, 
  it 
  is 
  more 
  than 
  I-*- 
  inch 
  deep. 
  The 
  inner 
  side 
  of 
  the 
  

   bone 
  is 
  concave 
  from 
  side 
  to 
  side 
  as 
  well 
  as 
  concave 
  from 
  back 
  to 
  

   front. 
  The 
  bones 
  meet 
  at 
  an 
  angle 
  of 
  120°. 
  

  

  The 
  pubis 
  is 
  thin, 
  and 
  only 
  the 
  posterior 
  portions 
  are 
  preserved 
  ; 
  

   the 
  antero-posterior 
  extent 
  of 
  the 
  symphysis 
  appears 
  to 
  be 
  about 
  

   6| 
  inches 
  ; 
  but 
  this 
  is 
  inferred 
  from 
  the 
  two 
  incomplete 
  bones. 
  

  

  The 
  bone 
  is 
  thickest 
  at 
  its 
  posterior 
  side 
  and 
  becomes 
  exceedingly 
  

   thin 
  anteriorly. 
  The 
  width 
  of 
  the 
  bone 
  from 
  the 
  posterior 
  point 
  of 
  

   the 
  symphysis 
  to 
  the 
  outermost 
  margin 
  of 
  the 
  femoral 
  articulation 
  

   is 
  8 
  inches; 
  the 
  ischiatic 
  union 
  extends 
  If 
  inch 
  behind 
  this 
  line; 
  and 
  

   its 
  innermost 
  margin 
  is 
  within 
  4| 
  inches 
  of 
  the 
  symphysial 
  line. 
  

   The 
  outer 
  margin 
  of 
  the 
  pubis 
  is 
  compressed 
  from 
  side 
  to 
  side, 
  and 
  

   directed 
  outward, 
  so 
  that 
  3| 
  inches 
  in 
  front 
  of 
  the 
  femoral 
  articula- 
  

   tion 
  the 
  concave 
  outer 
  margin 
  is 
  more 
  than 
  8| 
  inches 
  from 
  the 
  

   median 
  line. 
  Like 
  the 
  ischium, 
  the 
  bone 
  is 
  slightly 
  convex 
  on 
  its 
  

   external 
  side, 
  slightly 
  concave 
  on 
  its 
  abdominal 
  surface 
  ; 
  a 
  slightly 
  

   inflated 
  thickening 
  runs 
  parallel 
  to 
  the 
  lateral 
  border. 
  

  

  The 
  iliac 
  bones 
  are 
  7 
  inches 
  long. 
  The 
  articular 
  surfaces 
  appear 
  

   to 
  have 
  been 
  somewhat 
  expanded 
  so 
  as 
  to 
  extend 
  over 
  the 
  upper 
  

   part 
  of 
  the 
  head 
  of 
  the 
  femur 
  ; 
  but 
  it 
  is 
  difficult 
  in 
  the 
  present 
  state 
  

   of 
  the 
  specimens 
  to 
  determine 
  by 
  what 
  surfaces 
  each 
  could 
  have 
  

   joined 
  the 
  pubis 
  and 
  ischium 
  so 
  as 
  to 
  form 
  the 
  acetabulum. 
  

  

  Each 
  bone 
  is 
  compressed 
  from 
  side 
  to 
  side, 
  2| 
  inches 
  broad 
  at 
  the 
  

   proximal 
  end, 
  and 
  expanded 
  at 
  the 
  sacral 
  end 
  in 
  the 
  same 
  direction 
  

   to 
  a 
  width 
  of 
  two 
  inches, 
  its 
  least 
  width 
  in 
  the 
  middle 
  being 
  1^ 
  inch. 
  

   The 
  anterior 
  border 
  from 
  above 
  downward 
  has 
  a 
  slight 
  sigmoid 
  

   flexure 
  from 
  side 
  to 
  side 
  ; 
  but 
  its 
  anterior 
  lateral 
  margin 
  is 
  nearly 
  

   straight 
  and 
  about 
  6 
  inches 
  long. 
  The 
  posterior 
  margin 
  is 
  concave, 
  

   and 
  5 
  inches 
  long. 
  The 
  compressed 
  sacral 
  end 
  is 
  convex 
  from 
  before 
  

   backward, 
  and 
  inclined 
  backward. 
  Half 
  an 
  inch 
  below 
  the 
  upper- 
  

   most 
  margin 
  the 
  inner 
  side 
  shows 
  scars, 
  1 
  inch 
  long, 
  of 
  two 
  sacral 
  

   articulations. 
  

  

  The 
  Fore 
  Limb. 
  

   The 
  fore 
  limb 
  is 
  much 
  smaller 
  than 
  the 
  hind 
  limb. 
  The 
  humerus 
  

  

  