﻿A 
  PLESIOSAURIAN 
  FROM 
  THE 
  OXFORD 
  CLAY. 
  199 
  

  

  and 
  in 
  Teleosaurus. 
  The 
  basioccipital 
  condyle 
  is 
  short 
  from 
  front 
  

   to 
  back, 
  and 
  has 
  its 
  chief 
  extension 
  from 
  above 
  downwards, 
  in- 
  

   dicating 
  that 
  the 
  head 
  of 
  the 
  animal 
  had 
  more 
  vertical 
  than 
  lateral 
  

   movement 
  ; 
  the 
  condyle 
  is 
  margined 
  by 
  a 
  slight 
  depression. 
  The 
  

   under 
  surface 
  of 
  the 
  bone, 
  as 
  usual, 
  is 
  concave 
  from 
  side 
  to 
  side 
  and 
  

   prolonged 
  outward 
  and 
  downward 
  into 
  strong 
  short 
  lateral 
  processes. 
  

   The 
  exoccipital 
  bone 
  is 
  preserved 
  only 
  on 
  one 
  side, 
  where 
  it 
  is 
  

   slightly 
  fractured. 
  It 
  does 
  not 
  appear 
  to 
  be 
  perforated 
  for 
  the 
  

   hypoglossal 
  nerve 
  or 
  for 
  blood 
  vessels. 
  Its 
  external 
  surface 
  is 
  nar- 
  

   row, 
  flat, 
  and 
  inclined 
  obliquely 
  towards 
  the 
  median 
  line 
  of 
  the 
  

   cranium 
  ; 
  it 
  terminates 
  behind 
  in 
  a 
  sharp 
  border, 
  which 
  is 
  inclined 
  

   obliquely 
  inward 
  and 
  forward 
  so 
  as 
  to 
  make 
  the 
  foramen 
  magnum 
  

   pyriform. 
  

  

  The 
  anterior 
  nares, 
  which 
  are 
  imperfectly 
  preserved, 
  appear 
  to 
  be 
  

   small, 
  and 
  situate 
  3f 
  inches 
  from 
  the 
  anterior 
  termination 
  of 
  the 
  

   skull 
  and 
  about 
  1^ 
  inch 
  from 
  each 
  other. 
  

  

  Lower 
  Jaw. 
  

  

  The 
  lower 
  jaw 
  is 
  13 
  inches 
  long. 
  The 
  symphysis 
  is 
  2 
  inches 
  

   long, 
  with 
  the 
  symphysial 
  suture 
  obliterated. 
  In 
  length 
  the 
  rami 
  

   are 
  gently 
  convex 
  on 
  the 
  outer 
  side. 
  The 
  jaw 
  is 
  broadest 
  from 
  side 
  

   to 
  side 
  at 
  the 
  coronoid 
  process, 
  where 
  it 
  measures 
  6| 
  inches 
  in 
  

   width, 
  and 
  1| 
  inch 
  in 
  vertical 
  depth. 
  At 
  this 
  point, 
  on 
  the 
  under- 
  

   side 
  of 
  the 
  jaw, 
  the 
  dentary 
  bone 
  ceases 
  to 
  be 
  prolonged 
  backward 
  : 
  

   it 
  looks 
  obliquely 
  downward, 
  outward, 
  and 
  forward 
  ; 
  its 
  surface 
  is 
  

   rough, 
  and 
  towards 
  the 
  symphysis 
  is 
  pitted 
  with 
  the 
  apertures 
  of 
  

   blood-vessels 
  and 
  nerves. 
  On 
  the 
  underside 
  of 
  the 
  anterior 
  sym- 
  

   physial 
  part 
  of 
  the 
  jaw 
  a 
  concavity 
  runs 
  parallel 
  to 
  its 
  inner 
  

   border. 
  Each 
  ramus 
  appears 
  to 
  have 
  sockets 
  for 
  twenty-one 
  teeth. 
  

   The 
  portion 
  of 
  the 
  dentary 
  bone 
  interior 
  to 
  the 
  aveolar 
  margin 
  in 
  

   the 
  front 
  part 
  of 
  the 
  jaw 
  is 
  an 
  inch 
  wide, 
  becoming 
  narrower 
  be- 
  

   hind 
  ; 
  it 
  is 
  oblique 
  and 
  convex, 
  but 
  is 
  more 
  vertical 
  at 
  its 
  backward 
  

   extension. 
  At 
  4| 
  inches 
  behind 
  the 
  anterior 
  extremity 
  of 
  the 
  sym- 
  

   physis 
  it 
  is 
  overlapped 
  by 
  the 
  splenial 
  bone, 
  which 
  in 
  front 
  is 
  only 
  

   half 
  as 
  deep 
  as 
  the 
  inner 
  border 
  of 
  the 
  dentary 
  bone 
  which 
  it 
  over- 
  

   laps. 
  The 
  surfaces 
  of 
  both 
  dentary 
  and 
  splenial 
  bones 
  are 
  marked 
  

   with 
  the 
  canals 
  for 
  many 
  small 
  blood-vessels, 
  while 
  the 
  canal 
  for 
  

   Meckel's 
  cartilage 
  is 
  open 
  for 
  at 
  least 
  5 
  inches 
  in 
  front 
  of 
  the 
  articu- 
  

   lation 
  of 
  the 
  lower 
  jaw. 
  Posteriorly 
  to 
  the 
  coronoid 
  process 
  the 
  jaw 
  

   is 
  compressed 
  from 
  above 
  downward 
  so 
  as 
  to 
  be 
  only 
  1 
  inch 
  deep 
  ; 
  

   its 
  upper 
  part 
  is 
  formed 
  by 
  the 
  coronoid 
  bone, 
  its 
  lower 
  part 
  by 
  the 
  

   surangular 
  bone. 
  The 
  coronoid 
  appears 
  to 
  extend 
  backward 
  so 
  as 
  

   to 
  form 
  the 
  anterior 
  border 
  of 
  the 
  articulation 
  of 
  the 
  lower 
  jaw. 
  

   The 
  articular 
  surface 
  is 
  quadrate, 
  about 
  1-Jg- 
  inch 
  from 
  side 
  to 
  

   side, 
  and 
  less 
  than 
  1 
  inch 
  long 
  ; 
  it 
  is 
  concave 
  from 
  front 
  to 
  back, 
  

   with 
  a 
  slightly 
  elevated 
  oblique 
  ridge 
  passing 
  from 
  the 
  inner 
  an- 
  

   terior 
  corner 
  to 
  the 
  outer 
  posterior 
  side 
  ; 
  the 
  posterior 
  margin 
  of 
  

   the 
  articulation 
  is 
  elevated, 
  and 
  consists 
  of 
  an 
  inner 
  and 
  an 
  -outer 
  

   part. 
  The 
  articular 
  bone 
  appears 
  to 
  be 
  small, 
  thin 
  from 
  above 
  

  

  q2 
  

  

  