﻿414 
  PROCEEDINGS 
  OP 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  [June 
  22, 
  

  

  formed 
  of 
  the 
  same 
  kind 
  of 
  pebbles 
  as 
  -in 
  the 
  lower, 
  but 
  imbedded 
  

   in 
  a 
  softer 
  matrix, 
  it 
  being 
  of 
  a 
  consistence 
  similar 
  to 
  that 
  of 
  the 
  

   intercalated 
  and 
  overlying 
  sandstones. 
  Occupying 
  a 
  position 
  inter- 
  

   mediate 
  between 
  the 
  more 
  indurated 
  lower 
  and 
  the 
  softer 
  upper 
  strata 
  

   are 
  found 
  the 
  flaggy 
  beds 
  which 
  yield 
  the 
  well-known 
  Arbroath 
  

   paving-stones. 
  These 
  flaggy 
  beds, 
  although 
  rather 
  intercalated 
  than 
  

   interstratified 
  in 
  the 
  conglomerates, 
  are 
  of 
  great 
  extent 
  and 
  very 
  

   considerable 
  thickness, 
  especially 
  along 
  and 
  on 
  both 
  sides 
  of 
  the 
  

   anticlinal 
  line 
  of 
  Forfarshire 
  (its 
  position 
  is 
  pointed 
  out 
  in 
  the 
  paper 
  

   above 
  referred 
  to) 
  ; 
  they 
  consist 
  of 
  alternating 
  layers 
  of 
  shales 
  and 
  

   freestones. 
  The 
  freestones 
  are 
  sometimes 
  thick 
  and 
  solid-bedded, 
  

   affording 
  an 
  excellent 
  building-stone, 
  sometimes 
  raised 
  in 
  layers 
  thin 
  

   enough 
  to 
  be 
  generally 
  used 
  as 
  roofing-slates, 
  although 
  of 
  very 
  

   inferior 
  quality, 
  and 
  sometimes 
  of 
  sufficient 
  thickness 
  to 
  form 
  

   good, 
  but 
  rather 
  soft, 
  paving-stones. 
  The 
  shales 
  are 
  for 
  the 
  most 
  

   part 
  argillaceous, 
  generally 
  of 
  a 
  light 
  greenish, 
  occasionally 
  of 
  a 
  

   pink 
  colour, 
  and 
  are 
  locally 
  known 
  as 
  " 
  caulm." 
  These 
  beds 
  are 
  

   not 
  only 
  of 
  considerable 
  economic 
  value, 
  but 
  are 
  interesting 
  to 
  the 
  

   geologist 
  as 
  affording 
  almost 
  the 
  only 
  field 
  in 
  Forfarshire 
  for 
  the 
  

   labours 
  of 
  the 
  fossil-collector. 
  Generally, 
  organic 
  remains 
  in 
  any- 
  

   thing 
  approaching 
  to 
  a 
  good 
  state 
  of 
  preservation 
  are 
  rare, 
  and 
  can 
  

   only 
  be 
  procured 
  by 
  getting 
  the 
  quarrymen 
  to 
  preserve 
  such 
  things 
  

   as 
  may, 
  from 
  time 
  to 
  time, 
  turn 
  up. 
  It 
  is, 
  however, 
  different 
  in 
  a 
  

   deposit 
  at 
  Farnell, 
  where, 
  as 
  mentioned 
  in 
  the 
  same 
  paper, 
  the 
  Rev. 
  

   Hugh 
  Mitchell 
  first 
  discovered 
  remains 
  of 
  Acanthodian 
  Irishes 
  ; 
  also 
  

   in 
  some 
  localities 
  in 
  the 
  Sidlaws, 
  where 
  Mr. 
  Walter 
  M 
  c 
  Nicol 
  very 
  

   soon 
  after 
  discovered 
  similar 
  organisms 
  : 
  these 
  deposits 
  are 
  highly 
  

   fossiliferous. 
  I 
  have 
  lately 
  been 
  able 
  to 
  trace 
  their 
  connexion, 
  and 
  

   find 
  them 
  to 
  consist 
  of 
  one 
  very 
  extensive 
  and 
  highly 
  fossiliferous 
  

   Fish-bed, 
  holding 
  an 
  intermediate 
  position 
  among 
  the 
  flaggy 
  beds, 
  

   continuous 
  and 
  apparently 
  equally 
  extensive 
  with 
  them. 
  This 
  bed 
  

   is 
  composed 
  of 
  a 
  semicalcareous 
  shale, 
  some 
  bands 
  highly 
  calcareous 
  

   and 
  semicrystalline, 
  and 
  having 
  many 
  imbedded 
  nodules. 
  A 
  pecu- 
  

   liar 
  band 
  of 
  a 
  tenacious 
  light- 
  coloured 
  clay, 
  some 
  5 
  or 
  6 
  inches 
  in 
  

   thickness, 
  is 
  very 
  persistent 
  in 
  this 
  shale, 
  and 
  from 
  it 
  the 
  Fish-bed 
  

   may 
  be 
  readily 
  recognized 
  wherever 
  it 
  crops 
  out. 
  The 
  colour 
  of 
  these 
  

   calcareous 
  shales 
  varies 
  much 
  : 
  sometimes, 
  as 
  at 
  Farnell, 
  it 
  is 
  of 
  a 
  fine 
  

   cream-colour, 
  changing 
  to 
  a 
  dirty 
  grey 
  ; 
  often 
  it 
  is 
  of 
  a 
  dark 
  rusty 
  

   brown 
  ; 
  but 
  the 
  prevailing 
  colour 
  is 
  a 
  bright 
  deep 
  blue, 
  generally 
  

   mottled. 
  The 
  thickness 
  varies 
  from 
  3 
  to 
  8 
  feet. 
  Some 
  of 
  the 
  layers 
  

   are 
  exceedingly 
  fissile, 
  splitting 
  into 
  laminae 
  not 
  much 
  thicker 
  than 
  

   writing-paper. 
  I 
  have 
  now 
  found 
  this 
  Fish-bed 
  in 
  Canterland 
  Den 
  in 
  

   Kincardineshire, 
  near 
  Farnell, 
  at 
  Turin 
  Hill, 
  in 
  some 
  quarries 
  south 
  

   of 
  Forfar, 
  in 
  many 
  places 
  in 
  the 
  Sidlaws, 
  in 
  Balruddery 
  Den 
  in 
  

   Forfarshire, 
  and 
  in 
  Rossie 
  Den 
  in 
  Perthshire. 
  It 
  thus 
  extends 
  over 
  

   a 
  range 
  of 
  more 
  than 
  twenty 
  miles. 
  Tbe 
  above 
  localities 
  are 
  all 
  to 
  

   the 
  north 
  of 
  the 
  anticlinal 
  ; 
  it 
  has, 
  however, 
  been 
  observed 
  by 
  Mr. 
  

   M 
  c 
  Mcol 
  in 
  one 
  or 
  two 
  places 
  to 
  the 
  south 
  of 
  it. 
  Wherever 
  this 
  

   deposit 
  has 
  been 
  discovered, 
  it 
  abounds 
  in 
  Ichthyic 
  and 
  Crustacean 
  

   remains, 
  the 
  former 
  being 
  far 
  the 
  more 
  abundant. 
  

  

  