﻿198 
  H. 
  G. 
  SEELEY 
  ON 
  MUR^NOSATJRUS 
  LEEDSII, 
  

  

  bones 
  extend 
  back 
  to 
  the 
  nares 
  as 
  in 
  Plesiosaurus. 
  The 
  anterior 
  al- 
  

   veolar 
  border 
  is 
  convex 
  and 
  measures 
  2| 
  inches 
  round 
  the 
  lateral 
  curve 
  

   on 
  each 
  side. 
  The 
  posterior 
  median 
  bird-like 
  or 
  lizard-like 
  extensions 
  

   of 
  the 
  premaxillaries 
  (unless 
  they 
  are 
  nasals 
  blended 
  with 
  the 
  premax- 
  

   illaries) 
  are 
  narrow 
  and 
  smooth, 
  meet 
  each 
  other 
  in 
  a 
  penthouse 
  

   ridge 
  in 
  the 
  median 
  line 
  of 
  the 
  skull, 
  and 
  join 
  the 
  frontal 
  bones 
  at 
  a 
  

   distance 
  of 
  5 
  inches 
  from 
  the 
  rounded 
  extremity 
  of 
  the 
  snout 
  *. 
  The 
  

   frontal 
  bones 
  are 
  about 
  2f 
  inches 
  long, 
  and 
  terminate 
  backward 
  in 
  

   the 
  foramen 
  parietale, 
  the 
  posterior 
  border 
  of 
  which 
  is 
  formed 
  by 
  

   the 
  parietal 
  bones. 
  The 
  frontals 
  are 
  flattened 
  bones, 
  with 
  a 
  groove 
  

   on 
  each 
  side 
  of 
  a 
  slightly 
  elevated 
  median 
  ridge 
  ; 
  the 
  suture 
  between 
  

   them 
  is 
  distinct 
  ; 
  they 
  measure 
  1^ 
  inch 
  from 
  side 
  to 
  side 
  where 
  

   narrowest, 
  are 
  compressed 
  from 
  above 
  downward 
  ; 
  and 
  nearly 
  the 
  

   whole 
  of 
  the 
  outer 
  parts 
  of 
  the 
  under-surfaces 
  form 
  the 
  upper 
  bor- 
  

   ders 
  of 
  the 
  orbits 
  ; 
  the 
  sides 
  of 
  the 
  bones 
  are 
  subparallel 
  ; 
  they 
  are 
  

   slightly 
  concave 
  from 
  side 
  to 
  side. 
  They 
  may 
  have 
  small 
  distinct 
  

   supraorbital 
  ossifications 
  in 
  front, 
  above 
  the 
  orbits, 
  though 
  from 
  the 
  

   state 
  of 
  fracture 
  in 
  which 
  the 
  specimen 
  was 
  found 
  this 
  is 
  not 
  quite 
  

   certain. 
  From 
  the 
  posterior 
  angle, 
  in 
  which 
  they 
  join 
  the 
  parietal 
  

   bone, 
  the 
  narrow 
  postfrontal 
  bones 
  are 
  given 
  off. 
  The 
  postfrontals 
  

   are 
  then 
  directed 
  outward 
  and 
  slightly 
  forward, 
  and 
  are 
  traversed 
  by 
  

   a 
  ridge 
  which 
  divides 
  their 
  outside 
  surface 
  into 
  anterior 
  and 
  posterior 
  

   areas. 
  The 
  foramen 
  parietale 
  is 
  large, 
  and 
  is 
  directed 
  downward 
  

   and 
  backward, 
  increasing 
  in 
  size 
  as 
  it 
  descends. 
  The 
  parietal 
  bone 
  

   is 
  greatly 
  compressed 
  from 
  side 
  to 
  side, 
  forming 
  a 
  sharp 
  longitudinal 
  

   keel 
  above 
  ; 
  as 
  in 
  the 
  nearly 
  mature 
  fowl, 
  it 
  shows 
  no 
  trace 
  of 
  a 
  me- 
  

   dian 
  suture, 
  though 
  the 
  frontals 
  are 
  separate 
  ; 
  it 
  measures 
  2\ 
  inches 
  

   from 
  front 
  to 
  back, 
  and 
  terminates 
  posteriorly 
  in 
  a 
  straight, 
  transverse, 
  

   almost 
  smooth 
  and 
  flat, 
  vertical 
  suture 
  : 
  the 
  bone 
  widens 
  from 
  side 
  

   to 
  side 
  from 
  before 
  backward, 
  and 
  becomes 
  compressed 
  at 
  its 
  outer 
  

   posterior 
  border. 
  The 
  hinder 
  part 
  of 
  the 
  parietal 
  bone 
  is 
  occupied 
  

   on 
  the 
  underside 
  by 
  a 
  small 
  part 
  of 
  the 
  cerebral 
  surface. 
  This 
  is 
  

   concave 
  from 
  side 
  to 
  side, 
  and 
  straight 
  from 
  front 
  to 
  back, 
  with 
  a 
  

   slight 
  median 
  ridge. 
  This 
  surface 
  in 
  front 
  was 
  probably 
  occupied 
  

   by 
  the 
  small 
  lizard-like 
  cerebral 
  lobes 
  which, 
  as 
  among 
  Teleosaurs, 
  

   were 
  prolonged 
  forward 
  into 
  two 
  long 
  olfactory 
  nerves 
  ; 
  posteriorly 
  

   the 
  cerebral 
  surface 
  is 
  more 
  excavated, 
  seemingly 
  for 
  the 
  posterior 
  

   border 
  of 
  the 
  cerebral 
  lobes, 
  which 
  was 
  raised 
  above 
  the 
  portion 
  of 
  

   the 
  brain 
  which 
  succeeded 
  it 
  next 
  behind. 
  

  

  The 
  basisphenoid 
  is 
  united 
  by 
  suture 
  with 
  the 
  basioccipital 
  bone 
  ; 
  

   like 
  the 
  basisphenoid 
  of 
  Ichthyosaurus, 
  it 
  appears 
  to 
  be 
  perforated 
  by 
  

   the 
  carotid, 
  which 
  passes 
  obliquely 
  through 
  it. 
  The 
  basisphenoid 
  

   appears 
  to 
  be 
  underlapped 
  by 
  the 
  basitemporal 
  or 
  by 
  a 
  backward 
  

   prolongation 
  of 
  the 
  presphenoid 
  bone. 
  

  

  The 
  basioccipital 
  bone 
  is 
  1-J 
  inch 
  long. 
  It 
  is 
  remarkable 
  for 
  having 
  

   a 
  nearly 
  hemispherical 
  surface 
  for 
  the 
  occipital 
  condyle, 
  to 
  which 
  the 
  

   exoccipital 
  bones 
  do 
  not 
  contribute 
  as 
  they 
  do 
  in 
  many 
  Plesiosaurians 
  

  

  * 
  This 
  interpretation 
  differs 
  from 
  Prof. 
  Owen's 
  account 
  of 
  the 
  bones 
  in 
  Plesio- 
  

   saurus, 
  but 
  agrees 
  with 
  a 
  memorandum 
  of 
  my 
  own 
  on 
  the 
  bones 
  in 
  Plesiosaurus 
  

   Zetlandicus, 
  at 
  York. 
  

  

  