﻿OP 
  FIVE 
  GENERA 
  OF 
  MESOZOIC 
  REPTILES. 
  55 
  

  

  saurus 
  Crarriptoni 
  of 
  the 
  Upper 
  Lias, 
  which 
  Prof. 
  Seeley 
  has 
  made 
  

   the 
  type 
  of 
  the 
  genus 
  Bliomaleosaurus, 
  and 
  which 
  is 
  characterized 
  

   by 
  its 
  enormous 
  head 
  and 
  teeth, 
  short 
  mandibular 
  symphysis, 
  and 
  

   short 
  neck, 
  in 
  which 
  the 
  vertebrae 
  are 
  comparatively 
  few 
  in 
  number, 
  

   with 
  short 
  centra, 
  having 
  deeply 
  cupped 
  faces, 
  and 
  carrying 
  double 
  

   costal 
  facets, 
  and 
  with 
  firm 
  articulation 
  of 
  the 
  arches. 
  The 
  pecto- 
  

   ral 
  girdle 
  is 
  unknown 
  in 
  this 
  form 
  ; 
  but 
  in 
  the 
  Lower 
  Liassic 
  Plesio- 
  

   saurus 
  megacephalus, 
  as 
  well 
  as 
  in 
  the 
  closely 
  allied 
  P. 
  arcuatus 
  of 
  

   Owen, 
  in 
  which 
  the 
  head 
  and 
  neck 
  exhibit 
  all 
  the 
  generic 
  characters 
  

   of 
  the 
  so-called 
  Bliomaleosaurus, 
  this 
  part 
  of 
  the 
  skeleton 
  is 
  shown. 
  

   It 
  has 
  an 
  extremely 
  large 
  omosternum, 
  forming 
  a 
  shield-like 
  plate, 
  

   with 
  a 
  long 
  wide 
  notch 
  on 
  the 
  anterior 
  border, 
  and 
  apparently 
  

   consisting 
  of 
  a 
  single 
  element 
  ; 
  the 
  scapulas 
  and 
  coracoids 
  being 
  of 
  

   the 
  general 
  type 
  of 
  those 
  of 
  Plesiosaurus. 
  Mention 
  has 
  already 
  been 
  

   made 
  of 
  the 
  large 
  Sauropterygian 
  founded 
  upon 
  vertebras 
  and 
  teeth 
  

   from 
  the 
  Great 
  Oolite, 
  to 
  which 
  the 
  name 
  Thaumatosaurus 
  oolithicus 
  

   has 
  been 
  applied 
  ; 
  and 
  a 
  comparison 
  of 
  the 
  figures 
  of 
  these 
  speci- 
  

   mens 
  with 
  Plesiosaurus 
  Cramptoni 
  fails 
  to 
  show 
  even 
  a 
  specific 
  dis- 
  

   tinction 
  between 
  the 
  two, 
  although 
  this 
  might 
  be 
  indicated 
  if 
  fuller 
  

   materials 
  were 
  available. 
  Since, 
  therefore, 
  I 
  fail 
  to 
  see 
  any 
  charac- 
  

   ters 
  by 
  which 
  Bliomaleosaurus 
  can 
  be 
  distinguished 
  from 
  Thauma- 
  

   tosaurus, 
  I 
  can 
  but 
  include 
  the 
  former 
  in 
  the 
  latter 
  genus. 
  The 
  

   cervical 
  vertebrae 
  of 
  Thaumatosaurus, 
  although 
  they 
  agree 
  with 
  

   those 
  of 
  the 
  present 
  form 
  in 
  their 
  short 
  centra 
  and 
  double 
  costal 
  

   facets, 
  are 
  distinguished 
  by 
  their 
  deeply 
  cupped, 
  in 
  place 
  of 
  nearly 
  

   flat, 
  terminal 
  facets, 
  and 
  are 
  thereby 
  also 
  distinguished 
  from 
  

   those 
  of 
  Pliosaurus. 
  Vertebrae 
  of 
  the 
  type 
  of 
  those 
  of 
  Thaumato- 
  

   saurus 
  occur 
  from 
  the 
  Lias 
  to 
  the 
  Kimeridge 
  Clay, 
  the 
  species 
  

   of 
  the 
  latter 
  horizon 
  having 
  been 
  long 
  ago 
  described 
  by 
  Cuvier 
  

   as 
  Plesiosaurus 
  carinatus. 
  With 
  regard 
  to 
  the 
  generic 
  position 
  

   of 
  the 
  species 
  forming 
  the 
  subject 
  of 
  this 
  communication, 
  I 
  may 
  

   observe 
  that 
  before 
  I 
  had 
  satisfied 
  myself 
  as 
  to 
  the 
  difference 
  of 
  

   its 
  cervical 
  vertebrae 
  from 
  those 
  of 
  Thaumatosaurus, 
  and 
  also 
  as 
  

   to 
  the 
  nature 
  of 
  the 
  pectoral 
  girdle 
  of 
  any 
  of 
  the 
  species 
  which 
  I 
  

   include 
  in 
  the 
  latter, 
  I 
  considered 
  * 
  that 
  the 
  species 
  in 
  question 
  

   might 
  enter 
  that 
  genus, 
  since 
  I 
  did 
  not 
  regard 
  the 
  elongated 
  man- 
  

   dibular 
  symphysis 
  as 
  necessarily 
  indicative 
  of 
  generic 
  distinction. 
  

   The 
  pectoral 
  girdle 
  of 
  P. 
  arcuatus 
  is, 
  however, 
  so 
  totally 
  different 
  

   from 
  that 
  of 
  the 
  Oxfordian 
  form 
  that 
  I 
  can 
  no 
  longer 
  maintain 
  this 
  

   view; 
  especially 
  with 
  the 
  concomitant 
  difference 
  in 
  the 
  cervical 
  

   vertebrae. 
  I 
  cannot, 
  moreover, 
  very 
  well 
  include 
  the 
  present 
  form 
  

   in 
  Pliosaurus, 
  from 
  which 
  it 
  is 
  distinguished 
  by 
  the 
  firm 
  articulation 
  

   of 
  the 
  arches 
  with 
  the 
  centra 
  of 
  the 
  vertebrae, 
  and 
  the 
  longer 
  epipo- 
  

   dial 
  bones 
  ; 
  and 
  I 
  therefore 
  — 
  much 
  as 
  I 
  dislike 
  proposing 
  new 
  

   generic 
  terms 
  — 
  feel 
  bound 
  to 
  refer 
  it 
  to 
  a 
  new 
  genus, 
  for 
  which 
  I 
  

   think 
  the 
  name 
  Peloneustes 
  will 
  be 
  appropriate. 
  The 
  Kimeridgian 
  

   vertebra 
  to 
  which 
  Professor 
  Seeley 
  has 
  applied 
  the 
  name 
  Plesiosaurus 
  

   sterrodirus 
  will 
  belong 
  to 
  the 
  same 
  genus, 
  and 
  also 
  the 
  femur 
  

   described 
  by 
  Phillips 
  as 
  P. 
  cequalis. 
  

  

  * 
  Geol. 
  Mag. 
  decade 
  iii. 
  vol. 
  v. 
  p. 
  353 
  (1888). 
  

  

  