﻿PROF. 
  C. 
  LAPWORTH 
  ON 
  THE 
  GIRVAN 
  SUCCESSION. 
  597 
  

  

  abundant 
  to 
  cause 
  the 
  entire 
  series 
  to 
  weather 
  to 
  a 
  deep 
  rusty 
  

   colour. 
  

  

  2. 
  Whitehouse 
  Beds. 
  — 
  Crossing 
  the 
  sandy 
  floor 
  of 
  the 
  small 
  bay 
  of 
  

   Ardwell, 
  already 
  referred 
  to, 
  where 
  there 
  is 
  a 
  break 
  in 
  the 
  section 
  

   of 
  about 
  100 
  feet 
  in 
  calculated 
  thickness, 
  we 
  enter 
  next 
  upon 
  a 
  

   group 
  of 
  strata 
  of 
  a 
  totally 
  distinct 
  petrological 
  character. 
  This 
  

   new 
  group 
  has 
  here 
  a 
  collective 
  thickness 
  of 
  about 
  200 
  feet 
  ; 
  and 
  its 
  

   strata 
  are 
  easily 
  studied 
  at 
  many 
  points 
  along 
  the 
  coast-line 
  between 
  

   Ardwell 
  and 
  Shalloch 
  Mill. 
  Their 
  entire 
  thickness, 
  however, 
  is 
  

   shown 
  only 
  in 
  the 
  present 
  locality, 
  along 
  the 
  shore-line 
  between 
  

   Ardwell 
  Bay 
  and 
  the 
  old 
  ruin 
  of 
  Whitehouse, 
  which 
  is 
  built 
  upon 
  

   them, 
  and 
  after 
  which 
  I 
  have 
  named 
  them. 
  

  

  These 
  Whitehouse 
  Beds 
  consist 
  of 
  a 
  series 
  of 
  shales 
  and 
  mud- 
  

   stones, 
  of 
  colours 
  varying 
  from 
  bright 
  red 
  and 
  purple 
  to 
  greyish 
  

   green 
  and 
  black, 
  and 
  showing 
  numerous 
  intercalary 
  ribs 
  and 
  zones 
  

   of 
  grey 
  flagstone. 
  But 
  by 
  far 
  the 
  most 
  characteristic 
  feature 
  of 
  the 
  

   formation 
  is 
  the 
  frequent 
  presence 
  of 
  impure 
  calcareous 
  bands 
  or 
  

   11 
  cement-stones," 
  crowded 
  with 
  fragmentary 
  Brachiopods 
  and 
  Tri- 
  

   lobites. 
  

  

  The 
  entire 
  group 
  falls 
  very 
  naturally 
  into 
  two 
  main 
  divisions 
  — 
  a 
  

   lower 
  division 
  of 
  grey 
  shales 
  and 
  striped 
  flagstones, 
  and 
  an 
  upper 
  

   division 
  of 
  purple 
  and 
  green 
  mudstones. 
  

  

  Lower 
  Whitehouse 
  Beds 
  (Bb 
  1 
  ). 
  — 
  The 
  basal 
  band 
  of 
  this 
  subgroup 
  is 
  

   formed 
  of 
  striped 
  grey 
  and 
  green 
  somewhat 
  carbonaceous 
  shales, 
  

   much 
  softer 
  than 
  those 
  of 
  the 
  underlying 
  Ardwell 
  group, 
  from 
  the 
  

   terminal 
  beds 
  of 
  which 
  they 
  are 
  divided 
  by 
  the 
  sandy 
  beach 
  of 
  

   Ardwell 
  Bay. 
  They 
  contain 
  abundant 
  examples 
  of 
  Dicellograptus 
  

   Forchhammeri 
  &c. 
  

  

  The 
  middle 
  subdivision 
  is 
  characterized 
  as 
  a 
  whole 
  by 
  the 
  pre- 
  

   sence 
  of 
  numerous 
  ribs 
  of 
  calcareous 
  matter, 
  filled 
  with 
  small 
  pebbles, 
  

   and 
  yielding 
  a 
  few 
  fragmentary 
  Brachiopoda. 
  These 
  calcareous 
  

   zones 
  are 
  imbedded 
  in 
  masses 
  of 
  barren 
  greenish-grey 
  flagstones, 
  

   separated 
  by 
  striped 
  shales 
  destitute 
  of 
  all 
  traces 
  of 
  organic 
  remains. 
  

  

  The 
  commonest 
  fossils 
  I 
  have 
  been 
  able 
  to 
  collect 
  from 
  these 
  

   cement-beds 
  are 
  : 
  — 
  

  

  Leptaena 
  transversalis. 
  Orthis 
  calligramma. 
  

   sericea, 
  Sow. 
  Strophomena, 
  sp. 
  

  

  As 
  we 
  ascend 
  the 
  succession 
  the 
  hard 
  flaggy 
  ribs 
  become 
  more 
  

   closely 
  approximated, 
  but 
  otherwise 
  the 
  character 
  of 
  the 
  beds 
  

   remains 
  essentially 
  unmodified 
  for 
  about 
  100 
  feet 
  of 
  thickness. 
  

  

  They 
  are 
  followed 
  by 
  a 
  final 
  group 
  of 
  some 
  50 
  or 
  60 
  feet 
  of 
  strata 
  

   of 
  a 
  most 
  peculiar 
  character. 
  These 
  consist 
  of 
  soft 
  green 
  mud- 
  

   stones, 
  filled 
  with 
  a 
  multitude 
  of 
  hard 
  siliceous 
  ribs, 
  about 
  an 
  inch 
  

   in 
  thickness 
  and 
  one 
  or 
  two 
  inches 
  apart. 
  The 
  action 
  of 
  the 
  sea- 
  

   waves 
  has 
  dug 
  away 
  the 
  soft 
  mudstones 
  to 
  some 
  depth, 
  leaving 
  the 
  

   intervening 
  hard 
  ribs 
  projecting 
  in 
  long 
  jagged 
  parallel 
  lines 
  upon 
  

   the 
  floor 
  of 
  the 
  sea-platform, 
  giving 
  a 
  most 
  striking 
  appearance 
  to 
  

   the 
  little 
  group 
  as 
  here 
  exhibited. 
  

  

  Upper 
  Whitehouse 
  Beds 
  (Bb 
  2 
  ). 
  — 
  Next 
  succeeds 
  the 
  Upper 
  and 
  most 
  

  

  