﻿628 
  PROF. 
  C. 
  LAPWOETH 
  ON 
  THE 
  GIRT 
  AN 
  SUCCESSION. 
  

  

  are 
  well 
  displayed 
  in 
  the 
  branches 
  of 
  Baldrennan 
  Burn, 
  and 
  in 
  the 
  

   smaller 
  streams 
  which 
  drain 
  the 
  damp 
  slopes 
  of 
  Glenshalloch 
  Hill. 
  

  

  In 
  the 
  western 
  branch 
  of 
  Baldrennan 
  Burn 
  the 
  lowest 
  visible 
  

   strata 
  of 
  this 
  higher 
  subdivision 
  consist 
  of 
  yellow-weathering 
  pale- 
  

   hearted 
  flagstones, 
  which 
  are 
  essentially 
  identical 
  with 
  those 
  of 
  the 
  

   underlying 
  subgroup. 
  These 
  graduate 
  upwards 
  into 
  a 
  series 
  of 
  

   daik-grey 
  Graptolitic 
  shales, 
  which 
  extend 
  downwards 
  along 
  the 
  

   stream-course 
  for 
  a 
  distance 
  of 
  about 
  150 
  yards, 
  to 
  the 
  line 
  of 
  the 
  

   great 
  Craighead 
  fault, 
  where 
  they 
  are 
  crushed 
  against 
  a 
  series 
  of 
  

   flagstones, 
  shales, 
  and 
  impure 
  limestones, 
  that 
  possibly 
  appertain 
  to 
  

   the 
  Lower 
  Carboniferous 
  formations. 
  

  

  These 
  Graptolitic 
  shales 
  dip 
  at 
  a 
  steep 
  angle, 
  and 
  appear 
  to 
  bo 
  

   more 
  or 
  less 
  folded. 
  Their 
  united 
  thickness 
  may 
  be 
  estimated 
  at 
  

   about 
  200 
  feet. 
  

  

  Fossils 
  are 
  rare 
  ; 
  the 
  only 
  forms 
  are 
  Graptolithina. 
  These 
  occur 
  

   in 
  some 
  striped 
  seams 
  near 
  the 
  termination 
  of 
  the 
  visible 
  section. 
  

   The 
  chief 
  forms 
  collected 
  include 
  : 
  — 
  

  

  Enstrites 
  peregrinus, 
  Burr. 
  Monograptus 
  argutus, 
  Lapw. 
  

  

  Monograptus 
  crenularis, 
  Lapw. 
  Diplograptus 
  folium, 
  His. 
  

  

  leptotlieca, 
  Lapw. 
  taiuariscus, 
  Nick. 
  

  

  gregarius, 
  Lapw. 
  Climacograptus 
  scalaris, 
  His. 
  

  

  fimbriatus, 
  Inch. 
  E-etiolites. 
  

  

  Similar 
  strata 
  are 
  seen 
  again 
  in 
  the 
  normal 
  line 
  of 
  strike 
  in 
  the 
  

   Glenshalloch 
  branch 
  of 
  the 
  Baldrennan 
  Burn, 
  immediately 
  to 
  the 
  

   north 
  of 
  the 
  Craighead 
  fault, 
  extending 
  up 
  the 
  stream 
  for 
  some 
  

   distance. 
  The 
  beds 
  have 
  all 
  the 
  characteristics 
  of 
  those 
  of 
  the 
  last- 
  

   mentioned 
  locality, 
  and 
  afford 
  precisely 
  the 
  same 
  fossils. 
  

  

  The 
  same 
  Graptolitiferous 
  shales 
  are 
  laid 
  open 
  in 
  many 
  of 
  the 
  small 
  

   gullies 
  that 
  drain 
  Glenshalloch 
  AVood, 
  striking 
  in 
  various 
  directions 
  

   and 
  affording 
  presumptive 
  evidence 
  of 
  the 
  presence 
  of 
  several 
  cross 
  

   faults. 
  Along 
  the 
  roadway 
  west 
  of 
  the 
  burn 
  of 
  Glenshalloch 
  they 
  

   are 
  stained 
  of 
  a 
  purple 
  colour, 
  and 
  are 
  twisted 
  round 
  to 
  the 
  north- 
  

   west 
  over 
  the 
  arch 
  of 
  the 
  main 
  anticlinal 
  and 
  its 
  accompanying 
  

   faults. 
  The 
  beds 
  have 
  much 
  the 
  appearance 
  of 
  those 
  of 
  the 
  shaly 
  

   zones 
  of 
  the 
  Upper 
  Palaeozoic 
  rocks 
  of 
  the 
  neighbourhood, 
  and 
  

   appear 
  to 
  have 
  been 
  mapped 
  as 
  such 
  by 
  the 
  officers 
  of 
  the 
  Geological 
  

   Survey. 
  Their 
  lithological 
  character 
  and 
  the 
  occasional 
  Graptolites 
  

   they 
  contain, 
  however, 
  place 
  it 
  beyond 
  question 
  that 
  they 
  are 
  simply 
  a 
  

   slightly 
  discoloured 
  portion 
  of 
  the 
  Graptolitic 
  strata. 
  The 
  following 
  

   forms 
  have 
  been 
  collected 
  from 
  them 
  by 
  myself 
  : 
  — 
  

  

  Monagraptus 
  fimbriatus, 
  Nich. 
  Monograptus 
  leptotheca, 
  Lapw. 
  

   triangulatus, 
  Harkness. 
  Climacograptus 
  scalaris, 
  His. 
  

  

  These 
  Graptolitiferous 
  shales 
  are 
  the 
  highest 
  beds 
  of 
  Lower 
  Palaeo- 
  

   zoic 
  age 
  exposed 
  in 
  this 
  area. 
  The 
  remaining 
  angle 
  of 
  country 
  

   lying 
  between 
  Glenshalloch 
  Cottage 
  and 
  the 
  point 
  of 
  convergence 
  

   of 
  the 
  Craighead 
  and 
  High 
  Newlands 
  faults 
  is 
  wholly 
  covered 
  by 
  

   drift 
  and 
  brushwood. 
  

  

  Summary. 
  — 
  Our 
  study 
  of 
  the 
  fossiliferous 
  strata 
  of 
  the 
  Girvan 
  

   succession 
  exposed 
  in 
  the 
  inlier 
  of 
  Craighead 
  and 
  Mulloch 
  Hill 
  has 
  

   resulted 
  in 
  the 
  detection 
  of 
  an 
  easily 
  interpreted 
  ascending 
  sequence 
  

  

  