﻿662 
  PBOF. 
  C. 
  LAPWOETH 
  ON 
  THE 
  GIRVAN 
  SUCCESSION. 
  

  

  complete 
  investigation 
  in 
  the 
  field. 
  This 
  Barr 
  Series 
  includes 
  the 
  

   well-known 
  Craighead 
  or 
  Stinchar 
  Limestone 
  as 
  a 
  subordinate 
  

   member 
  near 
  its 
  base, 
  where 
  it 
  is 
  divided 
  from 
  the 
  underlying 
  

   Ballantrae 
  rocks 
  by 
  a 
  calcareous 
  conglomerate 
  and 
  breccia 
  of 
  

   irregular 
  thickness. 
  

  

  (ii) 
  The 
  tumultuous 
  Barr 
  Series 
  is 
  everywhere 
  conformably 
  sur- 
  

   mounted, 
  in 
  the 
  sections 
  of 
  the 
  Girvan 
  region, 
  by 
  a 
  second 
  series 
  

   (the 
  Ardmillan 
  Series), 
  composed 
  throughout 
  of 
  Graptolitic 
  flag- 
  

   stones 
  and 
  shales, 
  which 
  nevertheless 
  arrange 
  themselves 
  naturally 
  

   in 
  several 
  distinct 
  subformations 
  of 
  well-marked 
  petrological 
  cha- 
  

   racters. 
  The 
  higher 
  and 
  lower 
  divisions 
  of 
  this 
  great 
  series 
  (the 
  

   Ardwell, 
  Barren 
  Flagstone, 
  and 
  Drummuck 
  Beds) 
  have 
  their 
  re- 
  

   spective 
  systematic 
  positions 
  fixed 
  by 
  incontestible 
  stratigraphical 
  

   evidences. 
  The 
  proper 
  relations 
  of 
  its 
  central 
  divisions 
  (the 
  Cascade 
  

   and 
  Whitehouse 
  beds), 
  the 
  strata 
  of 
  which 
  are 
  usually 
  inverted, 
  are 
  

   established 
  mainly 
  by 
  geographical 
  considerations. 
  

  

  (lii) 
  The 
  Graptolitic 
  series 
  of 
  Ardmillan 
  visibly 
  underlies 
  a 
  third 
  

   series 
  (the 
  Neivlands 
  Series), 
  consisting 
  of 
  Brachiopod-sein.&stoiies, 
  

   Pentamerus-gxits, 
  and 
  Monoc/raptus-skales. 
  The 
  natural 
  place 
  of 
  

   the 
  first 
  (Mulloch-Hill 
  beds) 
  division 
  of 
  this 
  series 
  is 
  fixed 
  beyond 
  

   dispute 
  by 
  its 
  relation 
  to 
  the 
  terminal 
  beds 
  of 
  the 
  older 
  Ardmillan 
  

   series, 
  and 
  that 
  of 
  the 
  highest 
  division 
  (the 
  Oamregan 
  group) 
  by 
  its 
  

   relation 
  to 
  the 
  newer 
  Dailly 
  Series. 
  The 
  systematic 
  position 
  of 
  the 
  

   central 
  division 
  (the 
  Saugh-Hill 
  group) 
  is 
  deduced 
  with 
  equal 
  cer- 
  

   tainty 
  from 
  its 
  intermediary 
  place 
  in 
  the 
  series 
  ; 
  but 
  the 
  sequence 
  of 
  

   the 
  component 
  strata 
  of 
  this 
  central 
  division 
  is 
  rendered 
  so 
  dubious 
  

   by 
  inversion, 
  faulting, 
  and 
  local 
  unconformities, 
  that 
  we 
  are 
  unable 
  

   to 
  give 
  more 
  than 
  a 
  provisional 
  classification 
  of 
  its 
  minor 
  zones. 
  

  

  (iv) 
  Finally, 
  we 
  discern 
  a 
  fourth 
  petrological 
  series 
  (the 
  Dailly 
  

   Series), 
  at 
  once 
  the 
  thickest 
  and 
  most 
  homogeneous 
  series 
  in 
  the 
  

   Girvan 
  succession. 
  Its 
  place 
  at 
  the 
  summit 
  of 
  the 
  whole 
  is 
  esta- 
  

   blished 
  by 
  the 
  circumstances 
  that 
  it 
  forms 
  a 
  single 
  series 
  of 
  similar 
  

   strata, 
  which 
  is 
  wholly 
  distinct 
  from 
  either 
  of 
  the 
  series 
  below, 
  

   while 
  it 
  lies 
  on 
  the 
  southern 
  (or 
  upper) 
  side 
  of 
  the 
  Newlands 
  Series, 
  

   from 
  the 
  highest 
  zones 
  of 
  which 
  its 
  strata 
  appear 
  to 
  graduate 
  in 
  

   conformable 
  sequence. 
  

  

  (3) 
  In 
  place 
  of 
  an 
  enigmatical 
  group 
  of 
  Lower 
  Palaeozoic 
  rocks 
  

   of 
  no 
  great 
  vertical 
  thickness, 
  varying 
  locally 
  in 
  their 
  petrological 
  

   characters 
  to 
  an 
  extraordinary 
  extent, 
  and 
  containing 
  an 
  admixture 
  

   of 
  fossils 
  elsewhere 
  characteristic 
  of 
  formations 
  of 
  several 
  distinct 
  

   geological 
  epochs, 
  as 
  believed 
  by 
  some 
  of 
  the 
  earlier 
  students 
  of 
  these 
  

   beds, 
  we 
  find 
  an 
  orderly 
  arranged 
  sequence 
  of 
  strata 
  several 
  thousands 
  

   of 
  feet 
  in 
  vertical 
  thickness, 
  grouped 
  very 
  naturally 
  in 
  successive 
  

   formations 
  of 
  distinct 
  petrological 
  features, 
  each 
  formation 
  retaining 
  

   even 
  in 
  its 
  subordinate 
  zones 
  the 
  same 
  characters 
  over 
  the 
  entire 
  

   area, 
  and, 
  as 
  we 
  shall 
  show 
  in 
  the 
  second 
  part 
  of 
  this 
  memoir, 
  

   invariably 
  affording 
  the 
  same 
  special 
  group 
  of 
  fossils. 
  

  

  (4) 
  In 
  brief, 
  our 
  study 
  of 
  the 
  stratigraphical 
  relations 
  of 
  the 
  rocks 
  

   of 
  the 
  Girvan 
  succession 
  has 
  fully 
  established 
  the 
  following 
  propo- 
  

   sitions 
  : 
  — 
  

  

  