﻿426 
  PKOCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [June 
  22, 
  

  

  entire 
  length. 
  The 
  spines 
  are 
  all 
  straight 
  or 
  very 
  nearly 
  so, 
  hence 
  

   the 
  generic 
  name 
  (evdvs, 
  straight; 
  clkou-Vcl, 
  spine); 
  they 
  are 
  striated 
  

   longitudinally, 
  having 
  prominent 
  rounded 
  ridges, 
  and 
  in 
  most, 
  per- 
  

   haps 
  in 
  all, 
  these 
  ridges 
  are 
  perfectly 
  smooth. 
  The 
  anterior 
  dorsal 
  

   is 
  straight, 
  moderately 
  stout, 
  and 
  placed 
  well 
  back, 
  being 
  about 
  

   halfway 
  between 
  the 
  snout 
  and 
  the 
  commencement 
  of 
  the 
  tail. 
  The 
  

   posterior 
  dorsal 
  is 
  in 
  every 
  respect 
  similar 
  to 
  the 
  anterior, 
  but 
  con- 
  

   siderably 
  larger 
  ; 
  it 
  is 
  equal 
  in 
  length 
  to 
  about 
  one 
  -sixth 
  of 
  the 
  en- 
  

   tire 
  Fish, 
  and 
  is 
  placed 
  as 
  much 
  behind 
  the 
  anterior 
  dorsal 
  fin 
  as 
  this 
  

   is 
  behind 
  the 
  supra- 
  occipital 
  process. 
  The 
  anal 
  is 
  of 
  the 
  same 
  size 
  

   as, 
  and 
  otherwise 
  similar 
  to, 
  the 
  posterior 
  dorsal, 
  and 
  is 
  placed 
  some- 
  

   what 
  further 
  back. 
  The 
  ventral 
  spines, 
  about 
  two-thirds 
  the 
  length 
  

   of 
  the 
  anal, 
  are 
  placed 
  rather 
  more 
  than 
  their 
  own 
  length 
  in 
  advance 
  

   of 
  the 
  latter, 
  and 
  are 
  very 
  nearly, 
  if 
  not 
  quite, 
  straight. 
  The 
  pecto- 
  

   rals 
  are 
  intermediate 
  in 
  size 
  between 
  the 
  anterior 
  and 
  posterior 
  

   dorsals, 
  and 
  rather 
  stouter 
  ; 
  like 
  the 
  ventrals, 
  they 
  seem 
  to 
  have 
  the 
  

   slightest 
  possible 
  bend 
  backwards, 
  but 
  so 
  slight 
  as 
  to 
  be 
  scarcely 
  per- 
  

   ceptible. 
  The 
  pectorals 
  seem 
  to 
  have 
  articulated 
  with, 
  but 
  to 
  have 
  

   moved 
  independently 
  of, 
  the 
  coracoids, 
  not 
  being 
  anchylosed 
  as 
  in 
  

   some 
  of 
  the 
  other 
  genera. 
  Four 
  pairs 
  of 
  subordinate 
  spines, 
  having 
  

   much 
  the 
  character 
  of 
  the 
  ventrals, 
  but 
  shorter 
  and 
  stouter, 
  and 
  

   having 
  the 
  ridges 
  perhaps 
  somewhat 
  crenate, 
  are 
  placed 
  between 
  

   the 
  pectorals 
  and 
  ventrals. 
  The 
  fins 
  are 
  membranous 
  and 
  covered 
  

   with 
  exceedingly 
  minute 
  scales, 
  arranged 
  in 
  very 
  close, 
  straight 
  

   rows. 
  The 
  dorsal 
  fins 
  are 
  large, 
  the 
  posterior 
  very 
  large, 
  extending 
  

   much 
  beyond 
  and 
  above 
  its 
  spine. 
  Portions 
  of 
  the 
  pectorals 
  and 
  

   anal 
  are 
  preserved, 
  but 
  not 
  enough 
  to 
  show 
  their 
  size. 
  The 
  

   caudal 
  fin 
  is 
  placed 
  entirely 
  below, 
  and 
  is 
  not 
  large. 
  The 
  scales 
  are 
  

   very 
  small 
  and 
  rhomboidal 
  ; 
  two 
  or 
  three 
  rows, 
  arranged 
  longitudi- 
  

   nally, 
  and 
  of 
  rather 
  larger 
  size, 
  extend 
  from 
  the 
  first 
  dorsal 
  back- 
  

   wards 
  to 
  the 
  point 
  of 
  the 
  tail 
  ; 
  the 
  others 
  are 
  arranged 
  obliquely 
  

   across 
  the 
  body. 
  The 
  external 
  surface 
  of 
  the 
  scales 
  is 
  perfectly 
  

   smooth 
  and 
  shining, 
  ver} 
  r 
  considerably 
  rounded 
  and 
  raised 
  in 
  the 
  

   centre, 
  and, 
  although 
  in 
  well-preserved 
  specimens 
  the 
  character 
  of 
  

   this 
  surface 
  seems 
  eminently 
  ganoid, 
  imperfectly 
  preserved 
  patches 
  

   present 
  so 
  much 
  the 
  appearance 
  of 
  shagreen 
  that, 
  judging 
  from 
  

   my 
  earlier 
  and 
  less 
  perfectly 
  preserved 
  specimens, 
  I 
  had 
  no 
  doubt 
  that 
  

   this 
  Fish 
  belonged 
  to 
  the 
  Placoid 
  order. 
  The 
  inner 
  surface 
  is 
  very 
  

   markedly 
  sculptured 
  ; 
  well-defined 
  stria?, 
  from 
  five 
  to 
  six 
  in 
  number, 
  

   extending 
  from 
  the 
  anterior 
  margin, 
  which 
  is 
  somewhat 
  rounded, 
  to 
  

   about 
  the 
  centre 
  of 
  the 
  scales. 
  Some 
  specimens 
  show 
  indications 
  of 
  

   internal 
  structure, 
  but 
  in 
  all 
  this 
  is 
  very 
  indistinct 
  indeed. 
  

  

  I 
  have 
  added, 
  as 
  a 
  specific 
  affix 
  for 
  this 
  Fish, 
  the 
  name 
  of 
  Mr. 
  

   Walter 
  M 
  c 
  Nicol, 
  one 
  of 
  its 
  original 
  discoverers, 
  whose 
  industry 
  has 
  

   largely 
  contributed 
  towards 
  elucidating 
  the 
  nature 
  of 
  the 
  organic 
  

   remains 
  contained 
  in 
  the 
  Forfarshire 
  Old 
  Red, 
  and 
  to 
  whom 
  I 
  am 
  

   much 
  indebted 
  for 
  pointing 
  out 
  the 
  position 
  and 
  nature 
  of 
  the 
  bed 
  

   in 
  which 
  these 
  Ichthyolites 
  are 
  found. 
  

  

  Some 
  of 
  my 
  specimens 
  indicate 
  another 
  species 
  of 
  this 
  genus, 
  

   the 
  principal 
  difference 
  being 
  in 
  the 
  number 
  and 
  character 
  of 
  the 
  

  

  