﻿ASPIDOKHYXCHID^. 
  423 
  

  

  Aspidorhynchus 
  euodus, 
  Egerton. 
  

  

  [Plate 
  XVII. 
  figs. 
  6-10.] 
  

  

  1845. 
  Aspidorhynchus 
  euodus, 
  Sir 
  P. 
  Egerton, 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  

   vol. 
  i. 
  p. 
  231, 
  with 
  outline 
  figs. 
  

  

  Type. 
  Scales, 
  rostrum, 
  and 
  presymphysial 
  bone 
  ; 
  unknown. 
  

  

  An 
  imperfectly 
  known 
  species 
  of 
  moderate 
  size. 
  Cranium 
  rapidly 
  

   tapering 
  to 
  the 
  acute 
  rostrum, 
  which 
  projects 
  in 
  advance 
  of 
  the 
  

   mandible 
  to 
  an 
  extent 
  scarcely 
  exceeding 
  one-quarter 
  of 
  the 
  total 
  

   leugth 
  of 
  the 
  cranium 
  ; 
  cranial 
  bones 
  ornamented 
  with 
  granulations 
  

   and 
  short 
  longitudinal 
  rugae, 
  mandible 
  and 
  opercular 
  bones 
  almost 
  

   smooth 
  ; 
  presymphysial 
  bone 
  slender 
  and 
  tapering, 
  length 
  about 
  three 
  

   times 
  as 
  great 
  as 
  its 
  maximum 
  depth 
  ; 
  upper 
  laniary 
  teeth 
  at 
  the 
  

   base 
  of 
  the 
  rostrum, 
  one 
  tooth 
  at 
  the 
  dentary 
  symphysis, 
  and 
  a 
  

   single 
  tooth 
  at 
  the 
  proximal 
  end 
  of 
  the 
  presymphysial 
  bone 
  very 
  

   large, 
  the 
  principal 
  mandibular 
  teeth 
  of 
  the 
  dentary 
  bone 
  well 
  

   spaced 
  and 
  of 
  moderate 
  size. 
  Scales 
  feebly 
  rugose. 
  

  

  Form. 
  Sf 
  Log. 
  Oxfordian 
  ; 
  Wiltshire. 
  

  

  j^ll 
  the 
  following 
  specimens 
  were 
  obtained 
  from 
  Christian 
  

   Malford, 
  near 
  Chippenham 
  : 
  — 
  

  

  40518. 
  Imperfect 
  head 
  and 
  opercular 
  bones, 
  with 
  scattered 
  scales 
  

   and 
  ring-vertebrae. 
  The 
  tip 
  of 
  the 
  rostrum 
  is 
  broken 
  

   away, 
  and 
  the 
  whole 
  of 
  the 
  mandible, 
  except 
  the 
  presym- 
  

   physial 
  bone, 
  is 
  wanting. 
  The 
  pterygo-quadrate 
  arcade, 
  

   however, 
  and 
  the 
  dentigerous 
  base 
  of 
  the 
  rostrum 
  are 
  

   well-preserved. 
  The 
  skull 
  is 
  shown 
  of 
  the 
  natural 
  size 
  in 
  

   PL 
  XVJJL. 
  fig. 
  6. 
  The 
  characteristic 
  narrow 
  parasphenoid 
  

   (pas.) 
  is 
  exposed 
  in 
  the 
  middle 
  of 
  the 
  cranium 
  and 
  the 
  

   nasal 
  opening 
  (na.) 
  is 
  indicated 
  immediately 
  in 
  advance 
  

   of 
  the 
  orbit. 
  The 
  quadrate 
  bone 
  (qu.) 
  is 
  fan-shaped, 
  

   with 
  a 
  relatively 
  small 
  condyle. 
  The 
  ectopterygoid 
  (ecpt.) 
  

   is 
  toothless 
  behind, 
  where 
  deeply 
  expanded, 
  and 
  its 
  

   slender, 
  closely-set 
  teeth 
  gradually 
  increase 
  in 
  size 
  from 
  

   behind 
  forwards 
  : 
  it 
  meets 
  the 
  palatine 
  (pi.) 
  at 
  an 
  

   uncertain 
  point 
  in 
  front, 
  this 
  bone 
  bearing 
  a 
  single 
  large 
  

   tooth 
  posteriorly 
  and 
  a 
  regular, 
  close 
  series 
  of 
  small 
  

   teeth 
  anteriorly. 
  The 
  entopterygoid 
  (enpt.) 
  is 
  long 
  and 
  

   narrow, 
  but 
  imperfectly 
  exhibited, 
  and 
  the 
  metapterygoid 
  

   is 
  of 
  uncertain 
  form. 
  Overlying 
  the 
  operculum 
  of 
  the 
  

   left 
  side, 
  which 
  is 
  exposed 
  from 
  its 
  inner 
  face, 
  is 
  a 
  long, 
  

   narrow, 
  laminar 
  bone 
  (pt.), 
  tapering 
  above, 
  abruptly 
  

  

  