﻿PROF. 
  C. 
  LAPWORTH 
  ON 
  THE 
  GIRVAN 
  SUCCESSION. 
  

  

  Fig. 
  1. 
  — 
  Typical 
  Section 
  of 
  the 
  Strata 
  of 
  Benan 
  Bum. 
  

  

  SE. 
  

  

  N.w 
  

  

  Ac. 
  Green 
  Conglomerate 
  of 
  Benan 
  Hill. 
  

  

  Ab. 
  Stincbar 
  Calcareous 
  group 
  : 
  

   Ab 
  4 
  . 
  Did?/ 
  mogr 
  apt 
  us-shales. 
  

   Ab 
  3 
  . 
  Compact 
  Limestones. 
  

   Ab 
  2 
  . 
  Maclurea-heds. 
  

   Ab 
  1 
  . 
  Orthis-confinis 
  Flags. 
  

  

  Aa. 
  Kirkland 
  group 
  :— 
  

  

  Aa 
  2 
  . 
  Reel 
  and 
  grey 
  Sandstones. 
  

   Aa 
  1 
  . 
  Purple 
  Conglomerate. 
  

  

  are 
  more 
  or 
  less 
  calcareous 
  throughout, 
  effervescing 
  distinctly 
  on 
  

   the 
  application 
  of 
  acid. 
  

  

  They 
  contain 
  a 
  few 
  fossils, 
  principally 
  Graptolites, 
  and 
  those 
  

   Linguliforni 
  Brachiopoda 
  which 
  are 
  generally 
  found 
  in 
  Graptolitiferous 
  

   deposits. 
  The 
  Graptolites 
  are 
  procurable 
  in 
  fragments 
  only, 
  owing 
  

   to 
  the 
  easily 
  shattered 
  nature 
  of 
  the 
  shales 
  and 
  their 
  concretionary 
  

   structure, 
  which 
  render 
  it 
  a 
  matter 
  of 
  impossibility 
  to 
  obtain 
  a 
  flat 
  

   surface 
  of 
  large 
  extent 
  parallel 
  to 
  the 
  line 
  of 
  bedding. 
  But 
  this 
  

   defect 
  is 
  more 
  than 
  counterbalanced 
  by 
  the 
  fact 
  that 
  the 
  few 
  frag- 
  

   ments 
  obtainable 
  are 
  all 
  preserved 
  in 
  their 
  full 
  relief, 
  allowing 
  of 
  

   their 
  immediate 
  specific 
  identification. 
  

  

  The 
  forms 
  of 
  Graptolites 
  collected 
  by 
  myself 
  from 
  these 
  green 
  

   shales 
  at 
  this 
  spot 
  include 
  : 
  — 
  

  

  Didymograptus 
  superstes, 
  Lapw. 
  

   Dicellograptus 
  sextans, 
  Hall. 
  

   Clathrograptus 
  cuneiformis, 
  Lapw. 
  

  

  Grlossograptus 
  Hincksii, 
  Hopk. 
  

   Cryptograptus 
  tricornis, 
  Carr. 
  

   Diplograptus 
  rugosus, 
  Emm. 
  

  

  The 
  Brachiopoda 
  arc 
  of 
  few 
  species, 
  and 
  embrace 
  Atrotreta 
  

   Nicholsoni, 
  Dav., 
  Siphonotreta 
  micula, 
  and 
  a 
  few 
  forms 
  of 
  Lingu- 
  

   lida?. 
  

  

  Compact 
  and 
  nodular 
  Limestones. 
  — 
  Below 
  these 
  Didymograptus- 
  

   shales 
  we 
  come 
  suddenly 
  to 
  a 
  mass 
  of 
  pale 
  limestones 
  (Ab 
  2+3 
  ) 
  

   admirably 
  exposed 
  in 
  the 
  beds 
  of 
  the 
  little 
  rills, 
  in 
  several 
  artificial 
  

   quarries, 
  and 
  in 
  many 
  occasional 
  exposures 
  seen 
  below 
  the 
  cliffs 
  of 
  

   conglomerate 
  in 
  the 
  surrounding 
  slopes. 
  The 
  masses 
  of 
  pale 
  lime- 
  

   stone, 
  pitted 
  with 
  innumerable 
  superficial 
  depressions, 
  due 
  to 
  the 
  

  

  2p2 
  

  

  