﻿614 
  PROE. 
  C. 
  LAPWORTH 
  ON 
  THE 
  GIRVAN 
  SUCCESSION. 
  

  

  A 
  patch 
  of 
  unfossiliferous 
  strata, 
  probably 
  referable 
  to 
  the 
  lower 
  

   division 
  of 
  the 
  Barren-flagstone 
  beds 
  occurs 
  to 
  the 
  south-west 
  of 
  Brae 
  

   Hill. 
  It 
  is 
  cut 
  off 
  from 
  all 
  the 
  neighbouring 
  strata 
  by 
  faults 
  of 
  

   great 
  magnitude 
  ; 
  and 
  it 
  is 
  therefore 
  referred 
  to 
  this 
  division 
  with 
  

   some 
  doubt. 
  Good 
  exposures 
  of 
  its 
  beds 
  are 
  seen 
  in 
  Cuddystone 
  

   Glen 
  and 
  on 
  the 
  west 
  side 
  of 
  Brae 
  Hill. 
  The 
  strata 
  are 
  green 
  and 
  

   grey 
  shales, 
  with 
  occasional 
  beds 
  and 
  bands 
  of 
  flagstone, 
  all 
  totally 
  

   barren 
  of 
  recognizable 
  fossils, 
  and 
  altogether 
  very 
  similar 
  to 
  the 
  

   highest 
  zone 
  of 
  the 
  Barren-flagstone 
  group. 
  

  

  This 
  completes 
  our 
  survey 
  of 
  the 
  distribution 
  of 
  the 
  Graptolitic- 
  

   flagstone 
  series 
  south 
  of 
  the 
  Girvan 
  Valley. 
  The 
  remaining 
  strata 
  

   are 
  very 
  different 
  in 
  their 
  characters, 
  penological 
  and 
  palaeontolo- 
  

   gical, 
  from 
  those 
  we 
  have 
  studied 
  hitherto 
  ; 
  and 
  their 
  description 
  is 
  

   most 
  conveniently 
  deferred 
  until 
  we 
  have 
  made 
  out 
  the 
  arrangement 
  

   of 
  the 
  palaeozoic 
  strata 
  which 
  are 
  exposed 
  north 
  of 
  the 
  Girvan 
  Valley, 
  

   on 
  the 
  heights 
  of 
  Craighead 
  and 
  Quarrel 
  Hill, 
  whore 
  rocks 
  unques- 
  

   tionably 
  belonging 
  to 
  tbe 
  Ardmillan 
  -flagstone 
  series 
  are 
  exposed 
  in 
  

   several 
  localities, 
  with 
  clear 
  relations 
  to 
  the 
  overlying 
  strata. 
  

  

  (C.) 
  Description 
  of 
  the 
  Strata 
  oe 
  the 
  Northern 
  Inlier 
  of 
  

   Craighead 
  and 
  Glenshalloch. 
  

  

  The 
  Lower 
  Palaeozoic 
  strata, 
  whose 
  interrelationships 
  fall 
  next 
  to 
  

   be 
  described, 
  occur 
  in 
  the 
  prominent 
  heights 
  of 
  Craighead, 
  Quarrel 
  

   Hill, 
  and 
  Glenshalloch, 
  which 
  together 
  constitute 
  the 
  beautifully 
  

   wooded 
  ridge 
  that 
  forms 
  such 
  a 
  conspicuous 
  object 
  to 
  the 
  north 
  of 
  

   the 
  valley 
  of 
  Girvan, 
  a 
  few 
  miles 
  inland 
  from 
  the 
  mouth 
  of 
  the 
  river. 
  

   These 
  strata 
  form 
  a 
  well-marked 
  inlier, 
  which 
  is 
  bounded 
  on 
  all 
  

   sides 
  by 
  more 
  recent 
  beds 
  of 
  Old 
  Kcd 
  Sandstone 
  and 
  Carboni- 
  

   ferous 
  age 
  ; 
  and, 
  broadly 
  speaking, 
  it 
  may 
  be 
  said 
  that 
  they 
  are 
  

   arranged 
  in 
  a 
  dome-like 
  or 
  anticlinal 
  form. 
  The 
  longitudinal 
  axis 
  

   of 
  this 
  anticlinal 
  is 
  not 
  precisely 
  coincident 
  with 
  the 
  geographical 
  

   axis 
  of 
  the 
  ellipsoidal 
  area 
  occupied 
  by 
  the 
  Lower 
  Palaeozoic 
  strata, 
  

   but 
  lies 
  a 
  little 
  to 
  the 
  southward. 
  In 
  consequence 
  of 
  this 
  arrange- 
  

   ment 
  tho 
  strata 
  forming 
  the 
  southern 
  leg 
  of 
  the 
  anticlinal 
  have 
  a 
  

   short 
  curve 
  and 
  a 
  steep 
  dip 
  to 
  the 
  south-western 
  margin 
  of 
  the 
  area, 
  

   where 
  they 
  are 
  suddenly 
  cut 
  off 
  by 
  the 
  grand 
  boundary 
  fault 
  of 
  

   Kilkerran 
  and 
  Craighead. 
  Northwards, 
  however, 
  the 
  beds 
  have 
  a 
  

   gentle 
  inclination, 
  the 
  angle 
  of 
  dip 
  rarely 
  execeeding 
  45°, 
  and 
  

   being 
  sometimes 
  as 
  low 
  as 
  10° 
  or 
  12°. 
  

  

  The 
  axis 
  of 
  the 
  main 
  anticlinal, 
  instead 
  of 
  being 
  approximately 
  

   horizontal, 
  is 
  archlike, 
  being 
  depressed 
  in 
  both 
  directions 
  as 
  we 
  pass 
  

   along 
  it 
  from 
  its 
  central 
  point. 
  The 
  long 
  elliptical 
  dome 
  thus 
  origi- 
  

   nated 
  has 
  been 
  truncated 
  by 
  denudation 
  ; 
  and 
  its 
  component 
  beds 
  are 
  

   now 
  shown 
  upon 
  the 
  ground 
  as 
  a 
  series 
  of 
  concentric 
  shells 
  or 
  zones 
  

   of 
  strata 
  dipping 
  everywhere 
  outwards 
  off 
  the 
  central 
  parts 
  of 
  the 
  

   dome. 
  They 
  admit 
  of 
  minute 
  and 
  almost 
  complete 
  examination 
  in 
  

   several 
  localities. 
  The 
  general 
  coating 
  of 
  wood 
  and 
  turf, 
  however, 
  

   hides 
  some 
  of 
  the 
  inferior 
  beds 
  from 
  sight 
  in 
  tfee 
  eastern 
  and 
  southern 
  

   parts 
  of 
  the 
  area; 
  but 
  towards 
  the 
  north-east 
  a 
  long 
  and 
  easily 
  

  

  