﻿1864.] 
  , 
  POWRIE 
  FORFARSHIRE 
  FOSSILS. 
  419 
  

  

  ossified 
  cranial 
  bones, 
  and 
  in 
  the 
  exceptions 
  mentioned 
  the 
  traces 
  of 
  

   ossification 
  are 
  very 
  indistinct. 
  

  

  The 
  branchial 
  apparatus 
  seems 
  in 
  all 
  to 
  have 
  consisted 
  of 
  exposed 
  

   arches; 
  in 
  some 
  these 
  are 
  numerous 
  and 
  well 
  marked, 
  in 
  others 
  ob- 
  

   scure. 
  

  

  None 
  show 
  an 
  opercular 
  bone. 
  

  

  They 
  all 
  appear 
  to 
  have 
  possessed 
  sharp 
  conical 
  teeth; 
  in 
  Ischna- 
  

   canthus 
  they 
  are 
  large, 
  long, 
  and 
  curved. 
  

  

  None 
  seem 
  to 
  have 
  possessed 
  oral 
  appendages. 
  

  

  Acanthodes, 
  Agassiz. 
  

  

  The 
  only 
  species 
  yet 
  found 
  in 
  Forfarshire 
  is 
  the 
  Acanthodes 
  Mit- 
  

   chelli, 
  described 
  by 
  Sir 
  Philip 
  Egerton 
  in 
  the 
  Tenth 
  Decade 
  of 
  

   ' 
  Organic 
  Eemains.' 
  All 
  the 
  specimens 
  from 
  which 
  this 
  species 
  was 
  

   described 
  and 
  figured 
  were 
  from 
  Farnell; 
  some 
  of 
  them 
  had 
  the 
  

   scales 
  not 
  at 
  all 
  well 
  preserved 
  ; 
  and, 
  the 
  external 
  layer 
  having 
  been 
  

   destroyed, 
  they 
  present 
  under 
  the 
  microscope 
  somewhat 
  of 
  a 
  granular 
  

   appearance 
  ; 
  tbe 
  artist 
  has 
  thus 
  figured 
  them. 
  Specimens 
  from 
  other 
  

   localities, 
  with 
  the 
  scales 
  beautifully 
  preserved, 
  have 
  since 
  been 
  

   obtained, 
  which 
  show 
  that 
  both 
  the 
  outer 
  and 
  inner 
  surfaces 
  were 
  

   perfectly 
  smooth, 
  exhibiting 
  not 
  the 
  slightest 
  vestige 
  of 
  sculpturing 
  

   of 
  any 
  kind. 
  

  

  This 
  is 
  by 
  far 
  the 
  most 
  abundant 
  of 
  all 
  the 
  Fishes 
  found 
  in 
  For- 
  

   farshire. 
  It 
  seems 
  to 
  have 
  swam 
  in 
  considerable 
  swarms 
  or 
  shoals, 
  

   numbers 
  gathering 
  together 
  wherever 
  food 
  was 
  to 
  be 
  found. 
  On 
  

   one 
  small 
  slab, 
  less 
  than 
  8 
  inches 
  square, 
  in 
  my 
  possession, 
  covered 
  

   with 
  scales 
  and 
  other 
  remains 
  of 
  the 
  larger 
  Euthacanthus, 
  upwards 
  

   of 
  two 
  dozen 
  may 
  be 
  counted, 
  attracted 
  evidently 
  by 
  the 
  dead 
  Fish, 
  

   only 
  to 
  be 
  silted 
  up 
  and 
  entombed 
  with 
  the 
  Euthacanthus 
  on 
  which 
  

   they 
  feasted. 
  

  

  Ischnacanthus, 
  Powrie. 
  

  

  Body 
  slender, 
  fusiform 
  ; 
  head 
  long, 
  rather 
  depressed 
  ; 
  mouth 
  very 
  

   large, 
  opening 
  slightly 
  under 
  ; 
  teeth 
  long, 
  conical, 
  curved 
  back- 
  

   wards; 
  intermediate 
  teeth 
  sharply 
  pointed, 
  small, 
  conical; 
  fins 
  

   membranous, 
  each 
  preceded 
  by 
  a 
  long, 
  slender, 
  slightly 
  curved, 
  

   grooved 
  spine 
  ; 
  two 
  dorsals, 
  two 
  pectorals, 
  two 
  ventrals, 
  one 
  anal. 
  

   Anterior 
  dorsal 
  spine 
  about 
  halfway 
  between 
  the 
  pectorals 
  and 
  ven- 
  

   trals; 
  posterior 
  dorsal 
  longest, 
  slightly 
  behind 
  the 
  anal; 
  pectorals 
  long, 
  

   articulating 
  with 
  the 
  pectoral 
  bones. 
  Ventrals 
  small, 
  halfway 
  between 
  

   the 
  pectorals 
  and 
  the 
  anal 
  ; 
  anal 
  smaller 
  than, 
  and 
  in 
  advance 
  of, 
  the 
  

   posterior 
  dorsal. 
  Scales 
  smooth, 
  rhomboidal, 
  very 
  small. 
  Tail 
  elon- 
  

   gated, 
  heterocercal. 
  

  

  ISCHNACANTHUS 
  GRACILIS, 
  Powrie. 
  

  

  Ictinocephalus 
  granulatus, 
  Page. 
  

   Diplacanthus 
  gracilis, 
  Egerton. 
  

  

  Sir 
  Philip 
  Egerton 
  describes 
  this 
  species 
  (Tenth 
  Decade 
  of 
  * 
  Or- 
  

   ganic 
  Remains 
  '), 
  from 
  a 
  single 
  specimen 
  from 
  Farnell, 
  as 
  belonging 
  to 
  

   the 
  genus 
  Diplacanthus. 
  He 
  there 
  states 
  that 
  the 
  " 
  position 
  and 
  

   other 
  peculiarities 
  of 
  the 
  spines 
  may 
  hereafter 
  prove 
  of 
  generic 
  

  

  