﻿434 
  L. 
  C. 
  MIALL 
  ON 
  THE 
  REMAINS 
  OF 
  LAB 
  miNXHODONTA 
  

  

  fragment 
  cannot 
  be 
  determined 
  with, 
  certainty. 
  The 
  epiotic 
  is 
  pro- 
  

   duced 
  outwards 
  and 
  backwards 
  into 
  a 
  thin 
  expansion, 
  with 
  a 
  rounded 
  

   or 
  spatulate 
  outline. 
  The 
  sutures 
  run 
  in 
  narrow 
  continuous 
  grooves. 
  

   On 
  the 
  underside, 
  part 
  of 
  the 
  cerebral 
  surface 
  is 
  exposed. 
  Broken 
  

   surfaces 
  indicate 
  the 
  thick 
  vertical 
  walls 
  which 
  bounded 
  the 
  brain- 
  

   case 
  behind 
  and 
  on 
  one 
  side. 
  A 
  strong 
  descending 
  ridge 
  passes 
  from 
  

   the 
  lateral 
  wall 
  along 
  the 
  epiotic 
  process, 
  subsiding 
  towards 
  the 
  edge. 
  

   Part 
  of 
  the 
  passage 
  for 
  the 
  spinal 
  cord 
  is 
  probably 
  indicated 
  by 
  a 
  

   smooth 
  surface 
  internal 
  to 
  the 
  inner 
  end 
  of 
  the 
  posterior 
  vertical 
  

   wall. 
  Like 
  many 
  other 
  fossils 
  in 
  this 
  collection, 
  the 
  present 
  frag- 
  

   ment 
  can 
  only 
  be 
  fully 
  understood 
  when 
  future 
  discoveries 
  have 
  

   brought 
  other 
  and 
  more 
  perfect 
  examples 
  to 
  light. 
  

  

  Among 
  a 
  collection 
  of 
  Keuper 
  Labyrinthodonts, 
  forwarded 
  for 
  

   examination 
  by 
  the 
  Rev. 
  P. 
  B. 
  Brodie, 
  I 
  find 
  a 
  second 
  example 
  of 
  

   these 
  bones, 
  nearly 
  corresponding, 
  as 
  to 
  extent, 
  with 
  the 
  fossil 
  in 
  

   the 
  Warwick 
  Museum. 
  The 
  backward 
  projection 
  of 
  the 
  epiotic 
  is 
  

   broken 
  off. 
  The 
  bones 
  are 
  somewhat 
  larger 
  and 
  much 
  thicker 
  than 
  

   in 
  the 
  fossil 
  from 
  Blakedown 
  Hill. 
  The 
  sculpturing 
  is 
  coarser, 
  but 
  

   not 
  quite 
  so 
  well 
  denned. 
  It 
  is 
  impossible 
  as 
  yet 
  to 
  pronounce 
  as 
  

   to 
  the 
  species 
  of 
  either 
  fossil. 
  In 
  all 
  probability 
  both 
  are 
  referable 
  

   to 
  the 
  same 
  species 
  ; 
  but 
  even 
  this 
  is 
  not 
  quite 
  certain. 
  

  

  Transverse 
  Sections 
  of 
  Labyrinthodont 
  Teeth. 
  PI. 
  XXVIII. 
  

  

  By 
  permission 
  of 
  the 
  Curators 
  of 
  the 
  Warwick 
  Museum 
  two 
  con- 
  

   tiguous 
  teeth, 
  from 
  a 
  mandible 
  of 
  Diadetognathus, 
  have 
  been 
  cut 
  to 
  

   show 
  the 
  microscopic 
  structure. 
  Mr. 
  Thomas 
  Atthey 
  kindly 
  made 
  

   the 
  preparation 
  ; 
  and 
  to 
  his 
  skill 
  we 
  are 
  indebted 
  for 
  a 
  large 
  and 
  

   beautiful 
  section. 
  

  

  The 
  tooth 
  of 
  Diadetognathus 
  differs 
  from 
  that 
  of 
  any 
  other 
  Laby- 
  

   rinthodont 
  genus. 
  It 
  is 
  much 
  compressed, 
  antero-posteriorly, 
  at 
  

   the 
  base 
  ; 
  so 
  that 
  its 
  section 
  is 
  a 
  rectangle, 
  with 
  the 
  long 
  sides 
  per- 
  

   pendicular 
  to 
  the 
  axis 
  of 
  the 
  jaw. 
  Above, 
  the 
  tooth 
  gradually 
  

   becomes 
  conical. 
  The 
  external 
  surface 
  exhibits 
  numerous 
  strise, 
  

   but 
  no 
  conspicuous 
  ridges. 
  

  

  The 
  section 
  is 
  made 
  near 
  the 
  base 
  of 
  the 
  tooth. 
  The 
  dentine 
  is 
  

   much 
  folded 
  ; 
  but 
  there 
  are 
  many 
  intricacies 
  of 
  arrangement, 
  which 
  

   no 
  folding, 
  however 
  complicated, 
  can 
  explain. 
  No 
  pulp-cavity 
  is 
  

   visible 
  *. 
  

  

  Capitosamms, 
  to 
  judge 
  from 
  a 
  very 
  rough 
  figure 
  given 
  by 
  Quen- 
  

   stedt, 
  is 
  the 
  genus 
  nearest 
  to 
  Diadetognathus 
  in 
  respect 
  of 
  dental 
  

   structure 
  ; 
  but 
  the 
  resemblance 
  is 
  not 
  close. 
  

  

  No 
  tusk 
  of 
  Diadetognathus, 
  similar 
  to 
  those 
  which 
  occur 
  at 
  in- 
  

   tervals 
  among 
  the 
  serial 
  teeth 
  of 
  nearly 
  every 
  Labyrinthodont 
  genus, 
  

   has 
  yet 
  been 
  discovered. 
  When 
  the 
  fore 
  part 
  of 
  the 
  muzzle 
  shall 
  

   present 
  itself, 
  we 
  may 
  expect 
  to 
  find 
  palatal, 
  vomerine, 
  or 
  mandi- 
  

   bular 
  tusks. 
  

  

  * 
  It 
  must 
  be 
  borne 
  in 
  mind 
  that 
  no 
  opportunity 
  has 
  yet 
  occurred 
  of 
  ex- 
  

   amining 
  the 
  upper 
  part 
  of 
  the 
  tooth. 
  

  

  