﻿428 
  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [Jime 
  22, 
  

  

  containing 
  Cephalaspis 
  Lyelll 
  immediately 
  succeeding 
  those 
  having 
  

   Pterygotus 
  Anglicus 
  and 
  Parka 
  decipiens, 
  these 
  (Pterygotus, 
  Parka, 
  

   and 
  Cephalaspis) 
  are 
  always 
  associated 
  in 
  the 
  same 
  beds, 
  and 
  extend 
  

   through 
  all 
  the 
  fossiliferous 
  rocks 
  of 
  Forfarshire. 
  The 
  Crustacea 
  of 
  

   the 
  Lanarkshire 
  shales 
  are 
  undoubtedly 
  specifically 
  distinct 
  from 
  

   those 
  of 
  Forfarshire, 
  but 
  their 
  close 
  affinity 
  clearly 
  indicates 
  near, 
  

   if 
  not 
  immediate, 
  succession. 
  The 
  same 
  intimate 
  relations 
  of 
  the 
  

   Ichthyodorulites 
  of 
  the 
  Upper 
  Ludlow 
  bone-bed 
  with 
  those 
  of 
  For- 
  

   farshire 
  equally 
  point 
  to 
  the 
  same 
  succession. 
  The 
  Onchus 
  Mur- 
  

   chisoni, 
  0. 
  tenuistriatus, 
  and 
  similar 
  remains 
  are, 
  in 
  my 
  opinion, 
  

   undoubtedly 
  spines 
  of 
  Acanthodian 
  Fishes, 
  very 
  similar 
  to, 
  although 
  

   specifically, 
  if 
  not 
  generically, 
  distinct 
  from, 
  the 
  Acanthodians 
  of 
  

   Forfarshire. 
  

  

  A 
  connexion 
  similar 
  to 
  that 
  which 
  exists 
  between 
  the 
  Upper 
  Silu- 
  

   rian 
  of 
  Lanarkshire, 
  Ludlow, 
  &c, 
  and 
  the 
  lower 
  members 
  of 
  the 
  Old 
  

   Red 
  Sandstone 
  may 
  be 
  equally 
  distinctly 
  traced 
  between 
  these 
  latter 
  

   and 
  the 
  overlying 
  beds 
  of 
  Caithness-shire, 
  &c. 
  Indeed, 
  were 
  it 
  not 
  

   that 
  in 
  no 
  instance 
  has 
  any 
  organism 
  specifically 
  identical 
  yet 
  been 
  

   found 
  in 
  these 
  beds, 
  one 
  would 
  be 
  inclined 
  to 
  look 
  on 
  them 
  as 
  mere 
  

   portions 
  of 
  the 
  same 
  continuous 
  series. 
  In 
  their 
  leading 
  features 
  the 
  

   Acanthodes, 
  Ischnacanthus, 
  Euthacanthus, 
  &c. 
  of 
  Forfarshire 
  very 
  

   much 
  resemble 
  the 
  Acanthodes, 
  Diplacanihus, 
  Chei) 
  'acanthus, 
  &c. 
  of 
  

   the 
  newer 
  rocks 
  ; 
  -but 
  of 
  these 
  the 
  generic 
  characters 
  seem 
  to 
  me 
  so 
  

   marked 
  as 
  to 
  prove 
  that, 
  with 
  the 
  exception 
  of 
  Acanthodes, 
  all 
  the 
  

   organic 
  remains 
  yet 
  found 
  in 
  these 
  rocks 
  belong 
  to 
  distinct 
  genera. 
  

   Acanthodes, 
  as 
  already 
  noticed, 
  has 
  a 
  very 
  wide 
  range, 
  extending 
  

   upwards 
  into 
  rocks 
  of 
  the 
  Permian 
  era. 
  The 
  specific 
  distinctions 
  

   between 
  A. 
  MitchelU 
  of 
  Forfarshire 
  and 
  A. 
  pusillus, 
  A. 
  Peachii, 
  &c. 
  

   have 
  been 
  so 
  clearly 
  pointed 
  out 
  by 
  Sir 
  Philip 
  Egerton 
  that 
  I 
  need 
  

   only 
  here 
  refer 
  to 
  his 
  descriptions. 
  Wherever 
  the 
  Ichthyolites 
  of 
  

   Forfarshire 
  are 
  found, 
  1 
  terygotus 
  and 
  its 
  allied 
  genera 
  are 
  also 
  to 
  be 
  

   found. 
  In 
  none 
  of 
  the 
  Caithness-shire 
  Fish-beds 
  have 
  any 
  of 
  these 
  

   Crustacea 
  yet 
  been 
  discovered. 
  There 
  is 
  thus 
  a 
  decided 
  blank 
  

   between 
  the 
  Forfarshire, 
  which 
  may 
  be 
  looked 
  on 
  as 
  the 
  typical 
  

   lower, 
  and 
  the 
  Caithness 
  -shire 
  or 
  typical 
  middle 
  division 
  of 
  the 
  Old 
  

   lied 
  Sandstone, 
  making 
  the 
  triple 
  division, 
  in 
  the 
  mean 
  time, 
  at 
  all 
  

   events, 
  the 
  most 
  convenient, 
  as 
  being 
  the 
  most 
  marked 
  division 
  of 
  

   this 
  formation. 
  That 
  further 
  research 
  may 
  yet 
  give 
  us 
  the 
  want- 
  

   ing 
  links 
  between 
  these 
  lower 
  divisions 
  I 
  have 
  little 
  doubt 
  ; 
  were 
  

   this 
  accomplished, 
  it 
  might 
  be 
  advisable 
  to 
  restrict 
  these 
  to 
  two 
  

   great 
  divisions, 
  upper 
  and 
  lower, 
  marked 
  by 
  that 
  want 
  of 
  con- 
  

   formity 
  which 
  has 
  already 
  been 
  traced 
  in 
  most 
  localities 
  where 
  the 
  

   formation 
  is 
  largely 
  developed 
  and 
  has 
  been 
  carefully 
  wrought 
  out. 
  

   Each 
  of 
  these 
  divisions, 
  the 
  upper 
  and 
  lower, 
  would 
  again 
  be 
  sub- 
  

   divided 
  ; 
  but 
  this 
  is 
  anticipating. 
  

  

  I 
  have 
  little 
  doubt 
  that 
  the 
  overlying 
  unconformable 
  sandstones 
  

   and 
  conglomerates 
  of 
  Whiteness, 
  near 
  Arbroath, 
  given 
  in 
  Sir 
  Charles 
  

   LyelPs 
  section 
  (see 
  ' 
  Manual,' 
  5th 
  edit. 
  p. 
  48), 
  belong 
  to 
  the 
  upper 
  

   division 
  of 
  the 
  Old 
  Red 
  Sandstone, 
  of 
  which 
  the 
  Clashbennie 
  red, 
  

   and 
  Elgin 
  and 
  Dura 
  Den 
  yellow, 
  sandstones 
  may 
  be 
  considered 
  

  

  