﻿180 
  MR. 
  C. 
  W. 
  ANDREWS 
  ON 
  THE 
  STRUCTURE 
  [May 
  1897, 
  

  

  in 
  Peloneustes) 
  ; 
  they 
  do 
  not 
  appear 
  to 
  have 
  met 
  on 
  the 
  middle 
  line, 
  

   at 
  least 
  anteriorly, 
  as 
  in 
  the 
  smaller 
  form, 
  so 
  that 
  for 
  some 
  distance 
  

   there 
  was 
  a 
  narrow 
  median 
  vacuity. 
  Behind 
  this, 
  however, 
  they 
  

   unite 
  with 
  one 
  another 
  for 
  about 
  4 
  cm., 
  behind 
  which 
  again 
  they 
  

   are 
  separated 
  by 
  the 
  parasphenoid. 
  About 
  opposite 
  the 
  anterior 
  

   border 
  of 
  their 
  lateral 
  ramus, 
  that 
  is 
  relatively 
  farther 
  forward 
  

   than 
  in 
  Peloneustes, 
  their 
  median 
  borders 
  diverge 
  from 
  the 
  para- 
  

   sphenoid, 
  and 
  enclose 
  with 
  it 
  the 
  posterior 
  palatine 
  vacuities 
  

   (PI. 
  XII, 
  p.p.vac), 
  which 
  are 
  here 
  about 
  10 
  or 
  11 
  cm. 
  in 
  length. 
  

   The 
  posterior 
  union 
  of 
  the 
  pterygoids 
  over 
  the 
  basisphenoid 
  and 
  

   part 
  of 
  the 
  basioccipital 
  forms 
  a 
  suture 
  about 
  9 
  cm. 
  in 
  length, 
  the 
  

   posterior 
  portion 
  of 
  which 
  for 
  about 
  6 
  cm. 
  is 
  raised 
  into 
  a 
  thick 
  and 
  

   prominent 
  ridge. 
  In 
  front 
  this 
  forks 
  into 
  a 
  pair 
  of 
  crests, 
  which 
  

   curve 
  outward 
  through 
  about 
  a 
  quarter 
  of 
  a 
  circle, 
  forming 
  

   externally 
  the 
  hinder 
  border 
  of 
  the 
  lateral 
  ramus 
  of 
  the 
  bone. 
  

   This 
  crest 
  terminates 
  in 
  a 
  massive 
  tuberosity, 
  the 
  flattened 
  top 
  

   of 
  which 
  looks 
  downward 
  and 
  outward 
  ; 
  this, 
  together 
  with 
  a 
  

   similar 
  prominence 
  on 
  the 
  transpalatine, 
  forms 
  the 
  downwardly- 
  

   directed 
  process 
  corresponding 
  to 
  that 
  seen 
  on 
  the 
  palate 
  in 
  

   Peloneustes, 
  Splienodon, 
  and 
  many 
  other 
  reptiles. 
  

  

  The 
  outer 
  border 
  of 
  the 
  posterior 
  ramus 
  (fig. 
  2, 
  p. 
  181, 
  p.pt.) 
  

   is 
  thick 
  and 
  rounded 
  ; 
  posteriorly, 
  it 
  passes 
  into 
  the 
  backwardly- 
  

   produced 
  process, 
  the 
  distal 
  portion 
  of 
  which 
  underlies 
  and 
  unites 
  

   in 
  close 
  suture 
  with 
  the 
  broad, 
  forwardly-directed 
  process 
  from 
  the 
  

   inner 
  border 
  of 
  the 
  quadrate, 
  the 
  two 
  meeting 
  in 
  an 
  oblique 
  suture. 
  

  

  The 
  lateral 
  ramus 
  of 
  the 
  pterygoid 
  (fig. 
  2, 
  l.-pt.), 
  the 
  hinder 
  border 
  

   of 
  which 
  is 
  formed 
  by 
  the 
  curved 
  ridge, 
  as 
  above 
  described, 
  has 
  a 
  

   thin 
  external 
  edge 
  overlapping 
  the 
  inner 
  edge 
  of 
  the 
  transpalatine. 
  

   The 
  anterior 
  border 
  is 
  at 
  right 
  angles 
  to 
  the 
  skull-axis, 
  and 
  unites 
  

   with 
  the 
  palatine. 
  

  

  The 
  transpalatine 
  (PI. 
  XII 
  & 
  fig. 
  1, 
  p. 
  179, 
  trs.) 
  is 
  an 
  

   L-shaped 
  bone, 
  having 
  a 
  prominent 
  tuberosity 
  at 
  the 
  angle. 
  This 
  

   tuberosity, 
  as 
  above 
  mentioned, 
  forms 
  the 
  anterior 
  half 
  of 
  the 
  

   downwardly-directed 
  process 
  of 
  the 
  palate. 
  One 
  of 
  the 
  limbs 
  of 
  

   the 
  L 
  is 
  directed 
  forward, 
  the 
  other 
  outward 
  and 
  a 
  little 
  backward. 
  

   Of 
  the 
  former, 
  the 
  inner 
  edge 
  forms 
  a 
  sutural 
  overlap 
  upon 
  the 
  

   pterygoid, 
  while 
  the 
  outer 
  forms 
  the 
  inner 
  border 
  of 
  the 
  suborbital 
  

   vacuity. 
  The 
  outer 
  arm 
  joins 
  the 
  maxilla 
  and 
  possibly, 
  to 
  some 
  

   extent, 
  the 
  jugal, 
  but 
  its 
  exact 
  relations 
  to 
  this 
  latter 
  are 
  not 
  clear 
  ; 
  

   it 
  forms 
  the 
  posterior 
  boundarj^ 
  of 
  the 
  suborbital 
  vacuity. 
  

  

  On 
  the 
  dorsal 
  surface 
  of 
  the 
  pterygoid, 
  there 
  is 
  on 
  the 
  left 
  side 
  

   of 
  the 
  present 
  specimen 
  the 
  well-preserved 
  lower 
  half 
  of 
  the 
  

   epipterygoid 
  or 
  columella 
  cranii 
  (fig. 
  2, 
  col.). 
  Its 
  basal 
  portion 
  

   is 
  an 
  elongate 
  oval, 
  with 
  its 
  long 
  axis 
  antero-posterior, 
  and 
  its 
  

   anterior 
  edge 
  opposite 
  the 
  hinder 
  margin 
  of 
  the 
  lateral 
  ramus 
  of 
  the 
  

   pterygoid 
  ; 
  this 
  expanded 
  basis 
  forms 
  a 
  firm 
  junction 
  with 
  the 
  upper 
  

   surface 
  of 
  the 
  pterygoid. 
  In 
  its 
  middle 
  portion 
  the 
  bone 
  contracts 
  

   considerably 
  in 
  width, 
  but 
  its 
  antero-posterior 
  diameter 
  is 
  still 
  

   far 
  greater 
  than 
  its 
  width 
  from 
  side 
  to 
  side. 
  On 
  the 
  right 
  side 
  of 
  

   the 
  skull 
  it 
  can 
  be 
  seen 
  that 
  the 
  upper 
  end 
  of 
  the 
  epipterygoid 
  is 
  

  

  