﻿FROM 
  THE 
  KEEPER 
  SANDSTONE 
  OP 
  WARWICK. 
  425 
  

  

  7. 
  LABrRiNTHODOsr 
  leptognathtts, 
  Owen 
  — 
  parts 
  of 
  mandibular 
  rami. 
  

  

  Coton 
  End, 
  1873. 
  

  

  In 
  this 
  slab 
  are 
  imbedded 
  a 
  fragment 
  from 
  the 
  middle 
  of 
  a 
  left 
  

   ramus, 
  and 
  the 
  anterior 
  extremity 
  of 
  a 
  right 
  ramus 
  of 
  a 
  mandible 
  

   specifically 
  identical 
  with 
  that 
  figured 
  by 
  Prof. 
  Owen 
  as 
  Labyrin- 
  

   thodon 
  lejptognathus 
  *. 
  I 
  see 
  no 
  reason 
  to 
  doubt 
  its 
  specific 
  identity 
  

   with 
  the 
  portion 
  of 
  the 
  muzzle 
  to 
  which 
  the 
  same 
  name 
  is 
  given 
  f 
  ; 
  

   but 
  confirmation 
  by 
  a 
  microscopical 
  comparison 
  of 
  the 
  teeth 
  is 
  

   desirable. 
  The 
  present 
  fossil 
  contributes 
  nothing 
  of 
  importance 
  to 
  

   our 
  knowledge 
  of 
  the 
  species. 
  A 
  sculptured 
  tract, 
  belonging 
  to 
  the 
  

   angular 
  bone, 
  and 
  situate 
  in 
  advance 
  of 
  the 
  centre 
  of 
  radiation, 
  shows 
  

   that 
  the 
  ridges, 
  though 
  very 
  distinct, 
  are 
  closer 
  and 
  smaller 
  than 
  in 
  

   any 
  of 
  the 
  species 
  of 
  Mastodonsaurus. 
  Over 
  the 
  small 
  patch 
  which 
  

   remains 
  they 
  are 
  remarkably 
  continuous, 
  arid 
  appear 
  to 
  increase 
  by 
  

   intercalation, 
  not 
  by 
  anastomosis. 
  The 
  broken 
  posterior 
  end 
  of 
  the 
  

   larger 
  fragment 
  proves 
  that 
  about 
  the 
  middle 
  of 
  the 
  ramus 
  the 
  alve- 
  

   olar 
  canal 
  was 
  Xin. 
  deep 
  and 
  half 
  as 
  wide. 
  The 
  bases 
  of 
  two 
  tusks 
  

   appear 
  in 
  their 
  usual 
  position, 
  near 
  the 
  anterior 
  extremity 
  of 
  the 
  

   ramus 
  ; 
  and 
  the 
  row 
  of 
  serial 
  teeth 
  is 
  continued 
  outside 
  them, 
  nearly 
  

   or 
  quite 
  up 
  to 
  the 
  symphysis 
  J. 
  

  

  8. 
  Diadetognatktjs 
  varvicensis, 
  nov. 
  sp. 
  — 
  posterior 
  part 
  of 
  left 
  ra- 
  

  

  mus 
  of 
  mandible. 
  Coton 
  End, 
  1872. 
  PI. 
  XXVII. 
  figs. 
  3 
  A, 
  3P>. 
  

  

  After 
  prolonged 
  examination 
  and 
  comparison, 
  I 
  find 
  myself 
  com- 
  

   pelled 
  to 
  regard 
  this, 
  and 
  the 
  three 
  fragments 
  next 
  to 
  be 
  described, 
  

   as 
  belonging 
  to 
  a 
  new 
  genus 
  and 
  species. 
  It 
  is 
  to 
  be 
  regretted 
  that 
  

   the 
  characters 
  as 
  yet 
  made 
  out 
  should 
  be 
  so 
  imperfect 
  ; 
  they 
  are, 
  

   however, 
  irreconcilable 
  with 
  those 
  of 
  any 
  form 
  previously 
  described. 
  

  

  The 
  present 
  fossil 
  nearly 
  corresponds 
  as 
  to 
  size 
  and 
  extent 
  with 
  

   the 
  right 
  ramus 
  of 
  Mastodonsaurus, 
  described 
  above 
  (No. 
  6, 
  p. 
  422) 
  ; 
  

   the 
  subcutaneous 
  sculpture 
  and 
  the 
  smooth 
  tract 
  above 
  it, 
  where 
  the 
  

   mandible 
  is 
  overlapped 
  by 
  the 
  quadrato-jugal, 
  have 
  the 
  same 
  gene- 
  

   ral 
  character. 
  At 
  the 
  same 
  time 
  differences 
  are 
  perceived, 
  some 
  of 
  

   which 
  seem 
  to 
  be 
  of 
  generic 
  value. 
  With 
  respect 
  to 
  the 
  external 
  

   surface, 
  it 
  is 
  readily 
  seen 
  that 
  the 
  sculpture 
  upon 
  the 
  angular 
  bone 
  is 
  

   more 
  rounded 
  than 
  in 
  Mastodonsaurus 
  pachygnathus 
  ; 
  the 
  descend- 
  

   ing 
  mucous 
  canal 
  (d. 
  g.) 
  is 
  much 
  less 
  defined, 
  and 
  the 
  surface 
  behind 
  

   it, 
  instead 
  of 
  being 
  diversified 
  by 
  a 
  triangular 
  patch 
  of 
  sculpture, 
  is 
  

   nearly 
  smooth. 
  On 
  the 
  inner 
  side 
  of 
  the 
  ramus, 
  a 
  considerable 
  part 
  

   of 
  the 
  splenial 
  plate, 
  which 
  is 
  furnished 
  by 
  the 
  articular 
  and 
  angu- 
  

   lar 
  bones, 
  is 
  preserved. 
  An 
  internal 
  mandibular 
  foramen 
  can 
  be 
  

   distinguished, 
  the 
  posterior 
  edge 
  of 
  which 
  is 
  5| 
  in. 
  distant 
  from 
  the 
  

   extremity 
  of 
  the 
  postarticular 
  process, 
  while 
  its 
  lower 
  edge 
  de- 
  

   scends 
  within 
  | 
  in. 
  of 
  the 
  inferior 
  border 
  of 
  the 
  ramus. 
  The 
  in- 
  

  

  * 
  Trans. 
  G-eol. 
  Soc. 
  2nd 
  series, 
  vol. 
  vi. 
  pi. 
  xliv. 
  figs, 
  7-9. 
  

  

  t 
  Loc. 
  cit. 
  pi. 
  xliii. 
  figs. 
  1-3. 
  

  

  \ 
  The 
  fragment 
  described 
  by 
  Prof. 
  Owen 
  did 
  not 
  exhibit 
  this 
  character. 
  

   " 
  Owing 
  to 
  the 
  circumstance 
  of 
  the 
  anterior 
  part 
  of 
  the 
  jaw 
  having 
  been 
  broken, 
  

   it 
  cannot 
  be 
  determined 
  whether 
  any 
  of 
  the 
  smaller 
  or 
  serial 
  teeth 
  were 
  continued 
  

   external 
  to 
  the 
  large 
  anterior 
  tusks 
  &c." 
  — 
  Loc. 
  cit, 
  p. 
  522. 
  

  

  Q. 
  J. 
  G. 
  S. 
  No. 
  120. 
  2 
  h 
  

  

  