﻿PROF. 
  C. 
  LAPWORTH 
  ON 
  THE 
  GIRVAN 
  SUCCESSION. 
  551 
  

  

  west 
  of 
  Ayrshire 
  there 
  occur 
  representatives 
  of 
  Upper 
  Silurian, 
  

   Llandovery, 
  Caradoc, 
  and 
  Llandeilo 
  rocks 
  " 
  (p. 
  5). 
  

  

  During 
  the 
  last 
  twenty 
  years 
  the 
  more 
  prolific 
  fossil-bearing 
  strata 
  

   of 
  the 
  Girvan 
  region 
  have 
  been 
  most 
  successfully 
  searched 
  by 
  Mrs. 
  

   Gray, 
  the 
  wife 
  of 
  Mr. 
  Robert 
  Gray, 
  F.R.S.E., 
  of 
  Edinburgh, 
  herself 
  

   a 
  native 
  of 
  this 
  beautiful 
  district. 
  Aided 
  by 
  the 
  various 
  members 
  of 
  

   her 
  family, 
  she 
  has 
  collected 
  from 
  these 
  beds 
  a 
  magnificent 
  series 
  of 
  

   organic 
  remains 
  of 
  all 
  types, 
  numbering 
  at 
  present 
  between 
  20,000 
  

   and 
  30,000 
  specimens. 
  This 
  collection, 
  which 
  has 
  been 
  most 
  gene- 
  

   rously 
  placed 
  at 
  my 
  service 
  by 
  Mrs. 
  Gray, 
  is 
  at 
  present 
  under 
  pro- 
  

   cess 
  of 
  description 
  in 
  the 
  well-known 
  ' 
  Monograph 
  of 
  the 
  Silurian 
  

   Fossils 
  of 
  Girvan 
  ' 
  of 
  Nicholson 
  and 
  Etheridge, 
  and 
  will 
  be 
  noticed 
  

   more 
  fully 
  in 
  the 
  second 
  portion 
  of 
  the 
  present 
  memoir. 
  

  

  In 
  the 
  three 
  instalments 
  of 
  this 
  important 
  Monograph 
  of 
  the 
  

   Girvan 
  fossils 
  by 
  Professor 
  Nicholson 
  and 
  Mr. 
  R. 
  Etheridge, 
  Jun., 
  a 
  

   view 
  of 
  the 
  general 
  sequence 
  on 
  the 
  same 
  lines 
  as 
  those 
  sketched 
  out 
  

   by 
  Salter 
  is 
  advocated, 
  and 
  an 
  attempt 
  made 
  to 
  fix 
  with 
  more 
  definite 
  

   precision 
  the 
  geological 
  date 
  of 
  some 
  of 
  the 
  more 
  fossiliferous 
  zones. 
  

   Founding 
  upon 
  the 
  vertical 
  distribution 
  of 
  the 
  Trilobites, 
  Mr. 
  

   Etheridge 
  suggests 
  a 
  Lower 
  Bala 
  age 
  for 
  the 
  Stinchar 
  Limestone, 
  and 
  

   a 
  Caradoc 
  age 
  for 
  that 
  of 
  Craighead 
  and 
  the 
  Trilobite-flagstones 
  of 
  

   Penwhapple, 
  and 
  unites 
  the 
  Trinucleus-shaies 
  of 
  Drummuck, 
  the 
  

   shelly 
  Sandstones 
  of 
  Mulloch 
  Hill, 
  and 
  the 
  Pentamerus- 
  Grits 
  in 
  the 
  

   Llandovery. 
  Professor 
  Nicholson, 
  on 
  the 
  evidence 
  of 
  the 
  Corals, 
  

   parallels 
  the 
  Craighead 
  Limestone 
  and 
  Penwhapple 
  beds 
  (Balclat- 
  

   chie) 
  with 
  the 
  upper 
  part 
  of 
  the 
  Trenton 
  of 
  IST.E. 
  America, 
  and 
  

   classes 
  the 
  Mulloch-Hill 
  Sandstones 
  and 
  Pentamerus- 
  gritstones 
  and 
  

   their 
  equivalents 
  in 
  the 
  Upper 
  Llandovery 
  or 
  May-Hill 
  group. 
  

  

  The 
  remaining 
  palasontological 
  works 
  treating 
  of 
  the 
  fossils 
  of 
  the 
  

   district 
  will 
  here 
  be 
  passed 
  over, 
  as 
  none 
  of 
  them 
  deal 
  seriously 
  with 
  

   the 
  vexed 
  question 
  of 
  the 
  ascending 
  succession 
  *. 
  

  

  II. 
  Physical 
  Relations 
  or 
  the 
  Lower 
  Paleozoic 
  Rocks 
  

   op 
  the 
  Girvan 
  Region. 
  

  

  (A) 
  The 
  Ben 
  an 
  Conglomerate 
  and 
  its 
  associated 
  Strata. 
  

  

  In 
  attempting 
  the 
  development 
  of 
  the 
  true 
  physical 
  relationship 
  

   of 
  strata 
  so 
  crumpled 
  and 
  dislocated 
  as 
  those 
  of 
  the 
  Girvan 
  region, 
  

   our 
  first 
  task 
  is 
  to 
  select 
  some 
  definite 
  stratigraphical 
  zone, 
  as 
  

   general 
  datum-line 
  or 
  horizon 
  of 
  reference, 
  from 
  which 
  to 
  commence 
  

   our 
  labour, 
  and 
  to 
  which 
  to 
  refer, 
  as 
  often 
  as 
  occasion 
  requires, 
  the 
  

   several 
  results 
  of 
  our 
  more 
  detailed 
  investigations. 
  An 
  horizon 
  

   suitable 
  for 
  this 
  purpose 
  must, 
  almost 
  of 
  necessity, 
  be 
  composed 
  

   of 
  strata 
  of 
  a 
  lithological 
  character 
  sufficiently 
  striking 
  to 
  be 
  

   identifiable 
  upon 
  all 
  occasions 
  with 
  ease 
  and 
  certainty. 
  It 
  should 
  

   be 
  of 
  sufficient 
  thickness 
  to 
  form, 
  at 
  least, 
  a 
  distinctly 
  marked 
  

  

  * 
  A 
  list 
  of 
  21 
  palseontological 
  memoirs 
  bearing 
  upon 
  the 
  Girvan 
  fossils 
  will 
  

   be 
  found 
  in 
  the 
  Bibliography 
  appended 
  to 
  the 
  chapter 
  on 
  Silurian 
  Geology 
  

   inserted 
  in 
  the 
  ' 
  Catalogue 
  of 
  Western 
  Scottish 
  Fossils,' 
  1876, 
  pp. 
  25-28. 
  

  

  