﻿602 
  PROF. 
  C. 
  LAPWORTH 
  ON 
  THE 
  GIRVAN 
  SUCCESSION. 
  

  

  consist 
  of 
  pale-green 
  mudstones 
  and 
  very 
  thin 
  flags, 
  having 
  the 
  same 
  

   general 
  dip 
  and 
  strike 
  as 
  the 
  underlying 
  Whitehouse 
  Beds, 
  out 
  of 
  

   which 
  they 
  graduate 
  conformably. 
  These 
  shaly 
  beds 
  contain 
  fre- 
  

   quent 
  examples 
  of 
  the 
  enigmatical 
  fossil 
  Nematolites 
  Grayii, 
  a 
  form 
  

   that 
  preeminently 
  distinguishes 
  this 
  group 
  throughout 
  the 
  Girvan 
  

   region. 
  

  

  As 
  we 
  ascend 
  in 
  the 
  succession, 
  thick 
  beds 
  of 
  flagstone 
  gradually 
  

   make 
  their 
  appearance 
  among 
  the 
  mudstones, 
  with 
  which 
  they 
  agree 
  

   exactly 
  in 
  their 
  colour 
  and 
  composition, 
  but 
  are 
  somewhat 
  coarser 
  

   and 
  more 
  compact 
  in 
  texture. 
  At 
  first 
  these 
  ribs 
  o 
  v 
  f 
  flagstone 
  occur 
  

   regularly 
  at 
  intervals 
  of 
  about 
  3 
  feet, 
  and 
  are 
  usually 
  not 
  more 
  than 
  

   a 
  foot 
  in 
  thickness. 
  When 
  we 
  have 
  overpassed 
  the 
  central 
  line 
  of 
  

   the 
  group, 
  however, 
  the 
  ribs 
  rapidly 
  increase 
  both 
  in 
  abundance 
  

   and 
  in 
  individual 
  thickness, 
  so 
  that 
  finally 
  they 
  become, 
  physically, 
  

   much 
  more 
  important 
  than 
  the 
  mass 
  of 
  soft 
  shales 
  and 
  mudstones 
  in 
  

   which 
  they 
  are 
  intercalated. 
  Many 
  of 
  these 
  flaggy 
  beds 
  attain 
  here 
  

   a 
  thickness 
  of 
  from 
  3 
  to 
  4 
  feet, 
  while 
  the 
  intermediary 
  shales 
  have 
  

   dwindled 
  down 
  to 
  a 
  few 
  inches. 
  Near 
  the 
  summit 
  of 
  the 
  group, 
  

   however, 
  as 
  exhibited 
  along 
  the 
  coast-line, 
  the 
  flags 
  again 
  become 
  

   thinner 
  and 
  less 
  conspicuous, 
  and 
  the 
  shales 
  regain 
  their 
  normal 
  

   importance 
  in 
  the 
  succession. 
  

  

  This 
  band 
  of 
  Barren 
  Flagstones 
  forms 
  a 
  conspicuous 
  feature 
  on 
  the 
  

   surface 
  of 
  the 
  coast-section, 
  both 
  eastward 
  and 
  westward 
  from 
  their 
  

   typical 
  exposure 
  in 
  Woodland 
  Bay. 
  They 
  are 
  well 
  displayed 
  in 
  

   both 
  sides 
  of 
  Port 
  Cardloch, 
  following 
  immediately 
  upon 
  the 
  fossi- 
  

   liferous 
  zone 
  of 
  the 
  Whitehouse 
  Beds, 
  their 
  hard 
  ribs 
  standing 
  up 
  

   perpendicularly 
  on 
  the 
  rugged 
  coast-platform, 
  divided 
  from 
  each 
  

   other 
  by 
  the 
  deep 
  grooves 
  from 
  which 
  the 
  soft 
  intercalary 
  shales 
  

   have 
  been 
  eroded. 
  In 
  Whitehouse 
  Bay 
  also 
  they 
  are 
  shown 
  in 
  the 
  

   same 
  geological 
  position 
  ; 
  but 
  only 
  a 
  few 
  feet 
  of 
  their 
  lowest 
  zones 
  

   are 
  exposed, 
  even 
  at 
  low 
  water. 
  

  

  They 
  form 
  two 
  small 
  islands 
  in 
  Woodland 
  Bay, 
  in 
  which 
  their 
  

   hard, 
  thick-bedded 
  central 
  beds 
  are 
  prominently 
  shown. 
  

  

  In 
  the 
  fine 
  exposure 
  formed 
  by 
  the 
  rocky 
  floor 
  of 
  Myoch 
  Bay 
  

   their 
  basal 
  beds 
  of 
  soft 
  green 
  mudstones 
  are 
  seen 
  following 
  at 
  once 
  

   upon 
  the 
  fossiliferous 
  calcareous 
  beds 
  of 
  the 
  Whitehouse 
  group. 
  

   Here, 
  too, 
  they 
  yield 
  an 
  abundance 
  of 
  the 
  characteristic 
  fossil 
  

   Nematolites 
  Grayii, 
  Lapw., 
  and 
  an 
  occasional 
  example 
  of 
  Dicello- 
  

   graptus, 
  as 
  at 
  Woodland 
  Point. 
  

  

  Between 
  Shalloch 
  Mill 
  and 
  the 
  rock 
  of 
  Craigskelly 
  the 
  coast-line 
  

   turns 
  to 
  the 
  northward, 
  crossing 
  the 
  line 
  of 
  strike 
  of 
  these 
  beds. 
  

   The 
  central 
  beds 
  of 
  the 
  group 
  are 
  seen 
  in 
  one 
  or 
  two 
  spots 
  projecting 
  

   from 
  the 
  sandy 
  floor 
  of 
  the 
  bay, 
  and 
  ranging 
  thence 
  into 
  the 
  interior 
  

   of 
  the 
  country, 
  where 
  their 
  geographical 
  distribution 
  will 
  be 
  described 
  

   in 
  subsequent 
  paragraphs 
  of 
  this 
  memoir. 
  

  

  It 
  will 
  be 
  apparent 
  from 
  a 
  study 
  of 
  the 
  map 
  (PI. 
  XXIV.), 
  that 
  

   we 
  have 
  now 
  descrbed 
  all 
  the 
  strata 
  visible 
  along 
  the 
  coast-platform 
  

   between 
  Ardwell 
  and 
  Shalloch, 
  with 
  the 
  exception 
  of 
  those 
  occurring 
  

   at 
  the 
  extreme 
  point 
  of 
  Woodland 
  promontory, 
  the 
  island 
  of 
  Craig- 
  

   skelly 
  and 
  its 
  neighbours, 
  and 
  the 
  little 
  point 
  at 
  Shalloch 
  Forge. 
  It 
  

  

  