﻿Vol. 
  53.] 
  STRUCTURE 
  OF 
  THE 
  SKULL 
  OF 
  A 
  PLIOSAUR. 
  177 
  

  

  13. 
  On 
  the 
  Structure 
  of 
  the 
  Skull 
  of 
  a 
  Pliosaur. 
  By 
  C. 
  W. 
  

   Andrews, 
  Esq., 
  B.Sc, 
  E.G.S., 
  Assistant 
  in 
  the 
  Geological 
  

   Department, 
  British 
  Museum. 
  (Read 
  January 
  6th, 
  1897.) 
  

  

  [Plate 
  XII.] 
  

  

  In 
  the 
  present 
  communication 
  I 
  propose 
  to 
  give 
  a 
  short 
  account 
  

   of 
  the 
  cranial 
  structure 
  of 
  the 
  Plesiosaurian 
  reptile 
  known 
  as 
  

   Pliosaurus 
  ferooc 
  (Sauvage), 
  1 
  a 
  very 
  fine 
  skull 
  of 
  which 
  has 
  recently 
  

   been 
  acquired 
  by 
  the 
  British 
  Museum. 
  Like 
  so 
  many 
  other 
  

   reptilian 
  fossils 
  from 
  the 
  Oxford 
  Clay, 
  this 
  specimen 
  was 
  obtained 
  in 
  

   the 
  neighbourhood 
  of 
  Peterborough 
  by 
  A. 
  N. 
  Leeds, 
  Esq., 
  E.G.S., 
  who 
  

   has 
  expended 
  much 
  time, 
  patience, 
  and 
  skill 
  in 
  fitting 
  together 
  the 
  

   numerous 
  fragments 
  into 
  which 
  the 
  bones 
  were 
  found 
  broken. 
  

   The 
  result, 
  however, 
  is 
  well 
  worth 
  the 
  trouble 
  taken, 
  and 
  the 
  

   specimen 
  is 
  now 
  perhaps 
  the 
  finest 
  Pliosaur 
  skull 
  known. 
  The 
  

   extreme 
  length 
  from 
  the 
  occipital 
  condyle 
  to 
  the 
  anterior 
  extremity 
  

   is 
  112 
  cm., 
  while 
  the 
  width 
  at 
  the 
  quadrate 
  region, 
  perhaps 
  

   somewhat 
  exaggerated 
  by 
  crushing, 
  is 
  50 
  cm. 
  

  

  The 
  description 
  of 
  this 
  skull 
  is 
  facilitated 
  by 
  the 
  great 
  similarity 
  

   which 
  exists 
  between 
  it 
  and 
  that 
  of 
  Peloneustes 
  philarchus, 
  of 
  which 
  

   an 
  account 
  has 
  already 
  appeared. 
  2 
  This 
  similarity 
  is 
  so 
  striking 
  that 
  

   it 
  seemed 
  not 
  impossible 
  that 
  the 
  present 
  specimen 
  might 
  be 
  merely 
  

   the 
  skull 
  of 
  an 
  old 
  individual 
  of 
  Peloneustes 
  : 
  but 
  there 
  are 
  a 
  

   number 
  of 
  differences 
  which 
  tend 
  to 
  show 
  that 
  such 
  is 
  not 
  the 
  case. 
  

   In 
  the 
  first 
  place, 
  the 
  total 
  number 
  of 
  teeth 
  in 
  the 
  upper 
  jaw 
  of 
  

   Peloneustes 
  is 
  greater, 
  and 
  there 
  are 
  six 
  instead 
  of 
  five 
  in 
  the 
  

   premaxilla 
  ; 
  it 
  is, 
  however, 
  possible 
  that 
  a 
  premaxillary 
  tooth 
  

   might 
  be 
  lost 
  in 
  growth, 
  since 
  this 
  actually 
  occurs 
  in 
  Crocodiles 
  

   jporosus? 
  so 
  that 
  this 
  latter 
  point 
  is 
  of 
  less 
  importance 
  than 
  might 
  be 
  

   supposed. 
  Again, 
  in 
  Peloneustes 
  there 
  is 
  no 
  diastema 
  between 
  the 
  

   premaxillary 
  and 
  maxillary 
  alveoli, 
  and 
  the 
  variation 
  in 
  the 
  size 
  of 
  

   the 
  teeth 
  in 
  different 
  parts 
  of 
  the 
  jaw 
  is 
  less. 
  The 
  form 
  of 
  the 
  

   palatines 
  and 
  transpalatines 
  is 
  also 
  different. 
  Unfortunately 
  the 
  

   lower 
  jaw 
  and 
  all 
  the 
  rest 
  of 
  the 
  skeleton 
  is 
  missing 
  in 
  the 
  present- 
  

   instance, 
  so 
  that 
  the 
  length 
  of 
  the 
  symphysis 
  and 
  other 
  characters 
  

   pointed 
  out 
  by 
  Lydekker 
  are 
  not 
  available 
  for 
  the 
  determination 
  of 
  

   this 
  specimen. 
  

  

  It 
  may 
  be 
  remarked 
  that, 
  although 
  the 
  teeth 
  of 
  this 
  form 
  from 
  the 
  

   Oxford 
  Clay 
  of 
  Peterborough 
  agree 
  precisely 
  with 
  those 
  described 
  

   by 
  Sauvage 
  from 
  the 
  same 
  horizon 
  at 
  Boulogne, 
  under 
  the 
  name 
  

   Liopleurodon 
  feroxf 
  they 
  differ 
  considerably 
  from 
  those 
  from 
  the 
  

   Kimeridge 
  Clay, 
  upon 
  which 
  Owen 
  founded 
  the 
  genus 
  Pliosaurus, 
  

  

  1 
  See 
  Brit. 
  Mus. 
  Cat. 
  Foss. 
  Eept. 
  pt. 
  ii. 
  (1889) 
  p. 
  145. 
  

  

  2 
  Andrews, 
  Ann. 
  Mag. 
  Nat. 
  Hist. 
  ser. 
  6, 
  vol. 
  xvi. 
  (1895) 
  p. 
  242. 
  

  

  3 
  Boulenger, 
  'Fauna 
  and 
  Flora 
  of 
  British 
  India 
  : 
  Eeptilia 
  and 
  Batracbia' 
  

   (1890) 
  p. 
  5. 
  

  

  4 
  Bull. 
  Soe. 
  geol. 
  France, 
  ser. 
  3, 
  vol. 
  i. 
  (1873) 
  p. 
  378. 
  

  

  