﻿588 
  PROF. 
  C. 
  LAPWORTH 
  ON 
  THE 
  GIRT 
  AN 
  SUCCESSION. 
  

  

  dividing 
  fosbiliferous 
  shales 
  point 
  in 
  the 
  same 
  direction 
  ; 
  for 
  petro- 
  

   graphically 
  they 
  are 
  almost 
  identical 
  with 
  those 
  of 
  the 
  Didymograptus- 
  

   beds 
  which 
  underlie 
  the 
  great 
  conglomerate, 
  while 
  they 
  are 
  very 
  

   different 
  from 
  the 
  hard 
  flaggy 
  Graptolitic 
  shales 
  of 
  Penwhapple. 
  

   As 
  will 
  be 
  demonstrated 
  in 
  the 
  sequel, 
  the 
  palaeontological 
  evidence 
  

   is 
  even 
  more 
  strongly 
  in 
  favour 
  of 
  the 
  union 
  of 
  these 
  gritstones 
  and 
  

   shales 
  which 
  together 
  make 
  up 
  our 
  group 
  of 
  the 
  Balclatchie 
  Beds, 
  

   with 
  the 
  JStinchar 
  or 
  Barr 
  group 
  ; 
  for 
  the 
  majority 
  of 
  the 
  forms 
  

   knowu 
  from 
  these 
  beds 
  are 
  identical 
  with 
  those 
  of 
  the 
  Craighead 
  

   limestone. 
  

  

  This 
  fossiliferous 
  group 
  of 
  gritstones 
  and 
  shales 
  is 
  therefore 
  placed, 
  

   in 
  our 
  scheme 
  ^sce 
  Table, 
  fig. 
  31, 
  p. 
  (301), 
  at 
  the 
  summit 
  of 
  the 
  Barr 
  

   or 
  IStinchar 
  iSeries, 
  which 
  constitutes 
  the 
  first 
  great 
  division 
  of 
  the 
  

   Girvan 
  succession, 
  and 
  embraces 
  the 
  whole 
  of 
  the 
  strata 
  lying 
  be- 
  

   tween 
  the 
  base 
  of 
  the 
  Kirkland 
  Conglomerate 
  and 
  the 
  summit 
  of 
  

   these 
  Balclatchie 
  Beds. 
  

  

  2. 
  Barbae, 
  SfC. 
  — 
  The 
  line 
  of 
  boundary 
  between 
  the 
  great 
  sheet 
  of 
  

   Benan 
  Conglomerate 
  and 
  Graptolitic 
  flagstone, 
  ranging 
  from 
  Bal- 
  

   clatchie 
  Bridge 
  to 
  the 
  neighbourhood 
  of 
  Mill 
  end 
  erd 
  ale, 
  has 
  been 
  care- 
  

   fully 
  searched 
  by 
  myself 
  for 
  traces 
  of 
  the 
  Balclatchie 
  Beds; 
  but 
  such 
  

   exposures 
  as 
  do 
  occur 
  are 
  very 
  fragmentary 
  and 
  unsatisfactory. 
  

  

  These 
  highly 
  distinctive 
  and 
  continuous 
  sheets 
  of 
  strata 
  are 
  appa- 
  

   rently 
  separated 
  from 
  each 
  other 
  along 
  the 
  whole 
  of 
  this 
  extent 
  by 
  

   an 
  intermediate 
  baud 
  of 
  mixed 
  character. 
  Long 
  tongues 
  of 
  hard 
  

   gritstone 
  and 
  breccia 
  run 
  irregularly 
  into 
  the 
  edges 
  of 
  the 
  area 
  of 
  

   Graptolitic 
  flagstones 
  ; 
  and 
  irregular 
  patches 
  of 
  concretionary 
  shales 
  

   and 
  dark 
  Graptolitic 
  mudstones 
  destroy 
  the 
  regularity 
  of 
  the 
  margins 
  

   of 
  the 
  area 
  of 
  the 
  Benan 
  Conglomerate. 
  

  

  Broadly 
  speaking, 
  this 
  intermediate 
  band 
  is 
  largely 
  composed 
  

   of 
  the 
  green 
  grits 
  and 
  fossiliferous 
  mudstones 
  of 
  the 
  Balclatchie 
  

   Beds. 
  On 
  the 
  Doon 
  Hill, 
  they 
  lie 
  apparently 
  in 
  a 
  sharp 
  synclinal 
  

   in 
  the 
  conglomerate 
  itself, 
  while 
  the 
  fossil-bearing 
  shales 
  are 
  

   again 
  exposed 
  in 
  the 
  roadway 
  between 
  the 
  Dhu 
  Craig 
  and 
  the 
  

   water 
  of 
  Assel. 
  At 
  the 
  angle 
  of 
  the 
  same 
  road 
  about 
  half 
  a 
  mile 
  

   south-west 
  of 
  the 
  farmstead 
  of 
  Balclatchie, 
  the 
  green 
  fossiliferous 
  

   gritstone 
  and 
  conglomerate 
  are 
  seen, 
  containing 
  a 
  few 
  shells, 
  

   associated 
  with 
  green 
  concretionary 
  and 
  dark 
  laminated 
  Grap- 
  

   tolitic 
  mudstones, 
  and 
  clearly 
  interposed 
  between 
  the 
  Benan 
  rock 
  of 
  

   the 
  east 
  bank 
  of 
  the 
  stream, 
  and 
  the 
  sheet 
  of 
  flagstones 
  seen 
  in 
  the 
  

   numerous 
  quarries 
  opened 
  for 
  repairing 
  the 
  roadway. 
  

  

  Between 
  this 
  locality 
  and 
  the 
  farmhouse 
  of 
  Pinmery 
  there 
  are 
  

   numerous 
  exposures 
  of 
  the 
  Balclatchie 
  Beds. 
  In 
  the 
  steep 
  slopes 
  of 
  

   the 
  Assel, 
  about 
  a 
  quarter 
  of 
  a 
  mile 
  west 
  of 
  Pinmery, 
  the 
  highest 
  

   beds 
  of 
  the 
  Benan 
  Conglomerate 
  are 
  seen 
  to 
  the 
  north 
  of 
  the 
  

   Tramitchell 
  fault 
  in 
  several 
  quarries 
  and 
  natural 
  exposures. 
  They 
  

   are 
  harder 
  than 
  usual, 
  and 
  the 
  matrix 
  is 
  more 
  of 
  the 
  nature 
  of 
  a 
  

   coarse 
  greywacke. 
  The 
  included 
  boulders 
  are 
  of 
  great 
  size, 
  and 
  are 
  

   scattered 
  irregularly 
  through 
  the 
  mass 
  of 
  rock, 
  in 
  which 
  few 
  small 
  

   pebbles 
  are 
  visible. 
  Immediately 
  above 
  them 
  the 
  concretionary 
  

   and 
  shaly 
  Balclatchie 
  mudstones 
  are 
  seen 
  in 
  many 
  isolated 
  spots. 
  

   Thev 
  are 
  succeeded 
  at 
  once 
  by 
  coarse 
  green 
  partly 
  conglomeratic 
  

  

  