﻿424 
  PEOCEEDINGS 
  01? 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [June 
  22, 
  

  

  the 
  supra-occipital 
  process 
  ; 
  several 
  pairs 
  of 
  intermediate 
  dermal 
  

   spines 
  between 
  the 
  ventrals 
  and 
  anal. 
  

  

  Pabextts 
  ixcurvus, 
  Agassiz. 
  

  

  Head 
  medium 
  size, 
  compressed 
  ; 
  body 
  short, 
  compressed, 
  tapering; 
  

   tail 
  large, 
  very 
  deep 
  ; 
  anterior 
  dorsal 
  straight, 
  longitudinal 
  ridges 
  

   delicately 
  crenate 
  ; 
  other 
  spines 
  with 
  crenate 
  ridges 
  ; 
  four 
  pairs 
  of 
  

   intermediate 
  dermal 
  spines 
  ; 
  scales 
  medium-sized, 
  smooth 
  externally, 
  

   interior 
  surface 
  sculptured. 
  

  

  The 
  spine 
  so 
  named 
  by 
  Agassiz, 
  and 
  described 
  and 
  figured 
  from 
  a 
  

   Balruddery 
  specimen 
  now 
  in 
  the 
  collection 
  at 
  Possic 
  Priory 
  *, 
  is 
  

   evidently 
  the 
  anterior 
  dorsal 
  of 
  this 
  Fish. 
  Specimens 
  are 
  rare 
  ; 
  but, 
  

   when 
  found, 
  are 
  generally 
  moderately 
  entire. 
  

  

  In 
  this 
  species 
  the 
  head 
  is 
  medium- 
  sized 
  and 
  compressed 
  laterally. 
  

   The 
  eye-orbits 
  occupy 
  a 
  nearly 
  centrical 
  position 
  on 
  each 
  side, 
  and 
  

   are 
  large. 
  The 
  mouth 
  is 
  indistinct, 
  but 
  seems 
  to 
  have 
  been 
  small, 
  

   opening 
  rather 
  below. 
  The 
  teeth 
  I 
  have 
  never 
  seen. 
  The 
  branchial 
  

   arches 
  are 
  exposed, 
  small, 
  and 
  placed 
  immediately 
  behind 
  and 
  rather 
  

   below 
  the 
  eye-orbits; 
  in 
  a 
  specimen 
  where 
  they 
  are 
  well 
  preserved, 
  

   they 
  seem 
  to 
  be 
  eight 
  in 
  number. 
  The 
  body 
  is 
  laterally 
  compressed, 
  

   stout, 
  short, 
  and 
  deepest 
  immediately 
  under 
  the 
  anterior 
  dorsal, 
  the 
  

   depth 
  being 
  about 
  one-fourth 
  of 
  the 
  entire 
  length 
  of 
  the 
  Fish 
  ; 
  thence 
  

   it 
  rapidly 
  tapers 
  to 
  the 
  tail, 
  which 
  is 
  heterocercal, 
  large, 
  and 
  very 
  

   broad, 
  the 
  outline 
  both 
  above 
  and 
  below 
  curved 
  outwardly; 
  its 
  length 
  

   is 
  not 
  much 
  less 
  than 
  one-fourth 
  of 
  that 
  of 
  the 
  entire 
  Fish. 
  The 
  spines 
  

   consist 
  of 
  two 
  dorsals, 
  two 
  pectorals, 
  two 
  ventrals, 
  and 
  one 
  anal. 
  

   Four 
  pairs 
  of 
  dermal 
  spines 
  are 
  situated 
  between 
  the 
  pectorals 
  and 
  

   ventrals. 
  The 
  spines 
  are 
  all 
  striated 
  longitudinally, 
  and 
  have 
  crenate 
  

   ridges. 
  The 
  anterior 
  dorsal 
  is 
  very 
  long 
  and 
  stout, 
  its 
  length 
  being 
  

   nearly 
  one 
  -half 
  of 
  that 
  of 
  the 
  entire 
  Fish 
  ; 
  it 
  is 
  toothed 
  posteriorly, 
  

   and, 
  as 
  described 
  by 
  Agassiz, 
  the 
  teeth 
  are 
  rather 
  distant, 
  short, 
  stout, 
  

   sharp, 
  and 
  point 
  upwards, 
  " 
  arquees 
  en 
  haut." 
  It 
  is 
  situated 
  imme- 
  

   diately 
  behind 
  the 
  head, 
  and 
  opposite 
  to 
  the 
  pectorals, 
  and 
  is 
  per- 
  

   fectly 
  straight. 
  The 
  posterior 
  dorsal 
  is 
  situated 
  about 
  halfway 
  between 
  

   the 
  anterior 
  dorsal 
  and 
  the 
  commencement 
  of 
  the 
  caudal 
  fin, 
  and 
  

   is 
  quite 
  straight, 
  stout, 
  and 
  about 
  two-fifths 
  of 
  the 
  length 
  of 
  the 
  ante- 
  

   rior. 
  The 
  pectorals 
  are 
  attached 
  to 
  the 
  coracoids, 
  or 
  pectoral 
  bones 
  ; 
  

   they 
  are 
  large 
  and 
  much 
  bent, 
  resembling 
  in 
  form 
  those 
  of 
  Climatius 
  

   reticulatas. 
  The 
  ventrals, 
  of 
  medium 
  size, 
  stout, 
  and 
  curved 
  back- 
  

   wards, 
  are 
  placed 
  not 
  much, 
  if 
  at 
  all, 
  in 
  advance 
  of 
  the 
  posterior 
  

   dorsal. 
  The 
  anal 
  is 
  comparatively 
  small, 
  somewhat 
  curved, 
  and 
  not 
  

   much 
  behind 
  the 
  ventrals. 
  In 
  none 
  of 
  my 
  specimens 
  are 
  the 
  inter- 
  

   mediate 
  spines 
  well 
  preserved 
  ; 
  they 
  seem 
  to 
  have 
  been 
  short, 
  stout, 
  

   and 
  rather 
  curved. 
  The 
  fins 
  are 
  membranous, 
  and 
  covered 
  with 
  

   small 
  scales 
  arranged 
  in 
  wavy 
  lines 
  ; 
  the 
  fin 
  immediately 
  behind 
  the 
  

   enormous 
  anterior 
  dorsal 
  spine 
  is 
  small, 
  while 
  that 
  succeeding 
  the 
  

   small 
  posterior 
  dorsal 
  is 
  very 
  large, 
  extending 
  above 
  and 
  beyond 
  the 
  

   spine. 
  The 
  scales 
  are 
  rather 
  large, 
  and, 
  unlike 
  those 
  of 
  the 
  other 
  

   genera, 
  are 
  arranged 
  in 
  irregular 
  wavy 
  lines 
  both 
  on 
  the 
  body 
  and 
  

   * 
  ' 
  Yieux 
  Gres 
  Eouge,' 
  pi. 
  xsxiii. 
  fig. 
  27. 
  

  

  