﻿422 
  L. 
  C. 
  MTALL 
  ON 
  IHE 
  REMAINS 
  OP 
  LABYRINTHODONTA 
  

  

  The 
  outer 
  wall 
  of 
  the 
  auditory 
  fossa 
  is 
  constituted 
  by 
  a 
  somewhat 
  

   similar 
  vertical 
  buttress, 
  the 
  connexions 
  of 
  which 
  are 
  not 
  quite 
  clear. 
  

   The 
  internal 
  face 
  of 
  this 
  buttress, 
  which 
  forms 
  the 
  outer 
  boundary 
  

   of 
  the 
  fossa, 
  is 
  furnished 
  by 
  the 
  supratemporal 
  (S 
  T) 
  above, 
  and 
  by 
  the 
  

   postero-external 
  expansion 
  of 
  the 
  pterygoid 
  below. 
  The 
  fragment 
  

   of 
  the 
  pterygoid 
  which 
  remains 
  has 
  been 
  displaced 
  nearly 
  an 
  inch 
  

   forwards. 
  The 
  supratemporal 
  extends 
  over 
  the 
  whole 
  of 
  the 
  upper 
  

   part 
  of 
  the 
  surface 
  now 
  under 
  description, 
  and 
  joins 
  the 
  epiotic 
  in 
  the 
  

   anterior 
  angle 
  of 
  the 
  fossa. 
  The 
  inferior 
  surface 
  of 
  this 
  buttress 
  has 
  

   suffered 
  injury. 
  When 
  perfect, 
  it 
  probably 
  consisted 
  of 
  a 
  laterally 
  

   compressed 
  vertical 
  mass, 
  which 
  connected 
  the 
  superior 
  part 
  of 
  the 
  

   cranial 
  vault 
  with 
  the 
  pterygoid. 
  The 
  outer 
  surface 
  of 
  this 
  

   buttress 
  is 
  quite 
  smooth, 
  and 
  doubtless 
  served 
  for 
  muscular 
  

   attachment. 
  It 
  is 
  concave 
  from 
  above 
  downwards, 
  and 
  slightly 
  

   convex 
  from 
  before 
  backwards. 
  This 
  surface 
  formed 
  part 
  of 
  the 
  

   temporal 
  fossa, 
  being 
  overarched 
  in 
  this 
  part 
  of 
  its 
  extent 
  by 
  the 
  

   supratemporal 
  and 
  quadrato-jugal. 
  The 
  fractured 
  upper 
  and 
  outer 
  

   edge 
  of 
  the 
  fossil 
  shows 
  where 
  the 
  overarching 
  expansion 
  has 
  been 
  

   broken 
  off. 
  No. 
  3 
  nearly 
  represents 
  the 
  complementary 
  portion 
  of 
  

   the 
  skull 
  as 
  far 
  as 
  the 
  postero-external 
  angle, 
  but 
  belongs 
  to 
  the 
  

   other 
  side. 
  

  

  On 
  the 
  upper 
  surface 
  of 
  the 
  fossil, 
  which 
  is 
  sculptured 
  much 
  as 
  in 
  

   Mastodonsaurus, 
  the 
  sutures 
  bounding 
  the 
  epiotic, 
  squamosal, 
  and 
  

   supratemporal 
  can 
  be 
  clearly 
  seen. 
  A 
  corner 
  of 
  the 
  parietal 
  is 
  also 
  

   shown. 
  The 
  backward 
  extension, 
  or 
  horn, 
  of 
  the 
  epiotic 
  is 
  nearly 
  

   smooth 
  ; 
  it 
  has 
  lost 
  the 
  extremity. 
  The 
  auditory 
  fossa 
  passes 
  almost 
  

   insensibly 
  into 
  the 
  upper 
  surface 
  on 
  its 
  anterior 
  and 
  external 
  sides. 
  

   Internally, 
  the 
  broken 
  edge 
  of 
  the 
  epiotic 
  rises 
  abruptly. 
  

  

  The 
  under 
  surface 
  reveals 
  nothing 
  of 
  consequence, 
  in 
  addition 
  to 
  

   the 
  details 
  already 
  mentioned, 
  except 
  part 
  of 
  the 
  upper 
  wall 
  of 
  an 
  

   irregular 
  cavity 
  in 
  advance 
  of 
  the 
  auditory 
  fossa. 
  Beyond 
  a 
  general 
  

   reference 
  of 
  this 
  cavity 
  to 
  the 
  acoustic 
  chamber 
  it 
  would 
  be 
  unsafe 
  

   to 
  go 
  at 
  present. 
  

  

  6. 
  Mastodonsattrus 
  pachygnathtjs, 
  Owen 
  — 
  part 
  of 
  right 
  ramus 
  of 
  

   mandible. 
  Coton 
  End, 
  1856. 
  PI. 
  XXVI. 
  figs. 
  3 
  A, 
  3B. 
  

  

  The 
  first 
  of 
  a 
  numerous 
  and 
  highly 
  interesting 
  series 
  of 
  Labyrin- 
  

   thodont 
  mandibles, 
  which 
  I 
  shall 
  describe, 
  comprises 
  the 
  posterior 
  

   third 
  or 
  so 
  of 
  a 
  right 
  ramus. 
  The 
  outer 
  plate, 
  so 
  far 
  as 
  it 
  extends, 
  

   is 
  in 
  excellent 
  preservation, 
  though 
  its 
  inner 
  surface, 
  which 
  forms 
  

   part 
  of 
  the 
  wall 
  of 
  the 
  alveolar 
  canal, 
  is 
  obscured 
  by 
  matrix 
  ; 
  the 
  

   inner 
  plate 
  is 
  almost 
  entirely 
  gone. 
  The 
  articular 
  cavity 
  has 
  been 
  

   injured, 
  but 
  not 
  seriously, 
  while 
  the 
  postarticular 
  process, 
  which 
  

   yields 
  useful 
  characters 
  in 
  this 
  order, 
  is 
  almost 
  perfect. 
  

  

  The 
  external 
  surface 
  of 
  the 
  angular 
  bone 
  exhibits 
  a 
  remarkably 
  

   bold 
  sculpture, 
  which 
  radiates 
  from 
  a 
  point 
  upon 
  the 
  inferior 
  border 
  

   of 
  the 
  ramus, 
  about 
  5 
  inches 
  distant 
  from 
  its 
  posterior 
  extremity. 
  

   Near 
  the 
  centre 
  of 
  radiation 
  it 
  consists 
  of 
  deep 
  and 
  irregular 
  pits, 
  

   which 
  become 
  elongated, 
  especially 
  in 
  front, 
  as 
  they 
  recede 
  from 
  the 
  

   centre. 
  The 
  upper 
  half 
  of 
  the 
  external 
  surface 
  is 
  furnished 
  by 
  the 
  

  

  