﻿^Ol' 
  53'] 
  FAUNA 
  OF 
  THE 
  KEISLEY 
  LIMESTONE. 
  95 
  

  

  It 
  is 
  clear 
  that 
  the 
  bed 
  contains 
  a 
  fauna 
  with 
  Middle 
  and 
  Upper 
  

   Bala 
  rather 
  than 
  Lower 
  Bala 
  affinities 
  ; 
  and 
  the 
  occurrence 
  of 
  the 
  

   species 
  Staurocephalus 
  Murchisoni, 
  Phillipsinella 
  parabola, 
  JRemo- 
  

   pleurides 
  longicostatus, 
  and 
  SpJtwronites 
  pyriformis, 
  which 
  do 
  not 
  

   range 
  down 
  below 
  the 
  Upper 
  Bala, 
  points 
  to 
  the 
  inclusion 
  of 
  the 
  

   bed 
  in 
  the 
  Upper 
  Bala. 
  The 
  presence 
  of 
  some 
  Silurian 
  species 
  might 
  

   incline 
  us 
  to 
  assign 
  to 
  the 
  Keisley 
  Limestone 
  a 
  somewhat 
  high 
  

   position 
  in 
  the 
  Upper 
  Bala 
  ; 
  but 
  on 
  comparing 
  the 
  lists 
  of 
  the 
  fossils 
  

   from 
  the 
  Staurocephalus-zone 
  and 
  the 
  Ashgill 
  Shales 
  in 
  England 
  and 
  

   Wales 
  with 
  the 
  list 
  from 
  the 
  Keisley 
  bed, 
  it 
  is 
  at 
  once 
  apparent 
  that 
  

   the 
  relationship 
  is 
  much 
  closer 
  with 
  the 
  former 
  than 
  with 
  the 
  latter. 
  

  

  Thus, 
  in 
  the 
  Stam-ocephalus-zone, 
  we 
  find 
  the 
  following 
  Keisley 
  

   species 
  present 
  : 
  — 
  

  

  Christiania 
  tenuicincta. 
  

   Orthis 
  calligramma. 
  

  

  „ 
  elegantula. 
  

  

  „ 
  testudinaria. 
  

   Leptcsna 
  rhomboidalis. 
  

   Tlectambonites 
  quinquecostata. 
  

   Halysites 
  catemdaria. 
  

   Stenopora 
  fibrosa. 
  

  

  longicostatus. 
  

   lllcenus 
  Bowmani. 
  

   Lichas 
  laxatus. 
  

   Phillipsinella 
  parabola. 
  

   Cheirurus 
  bimucronatus. 
  

  

  „ 
  juvenis 
  (=clavifrons, 
  ? 
  Palm.) 
  

   Staurocephalus 
  Murchisoni. 
  

   Sphcsrexochus 
  mirus. 
  

  

  In 
  the 
  Ashgill 
  Shales 
  and 
  Redhill 
  Beds, 
  on 
  the 
  other 
  hand, 
  only 
  

   the 
  following 
  Keisley 
  species 
  are 
  present 
  : 
  — 
  

  

  Calymene 
  Blumenbachi. 
  

   Cheirurus 
  clavifrons. 
  

   Orthis 
  ActonicB. 
  

  

  „ 
  alternata. 
  

  

  ,, 
  biforata. 
  

  

  „ 
  calligramma. 
  

  

  Orthis 
  elegantula. 
  

  

  „ 
  testudinaria. 
  

  

  „ 
  vespertilio. 
  

   Leptcsna 
  rhomboidalis. 
  

   Christiania 
  tenuicincta. 
  

   Holopea 
  concinna. 
  

  

  The 
  argillaceous 
  instead 
  of 
  calcareous 
  nature 
  of 
  the 
  sediment, 
  

   and 
  the 
  different 
  conditions 
  of 
  deposition, 
  undoubtedly 
  have 
  much 
  

   to 
  do 
  with 
  the 
  different 
  facies 
  of 
  the 
  Ashgill 
  Shale 
  fauna. 
  There 
  

   are, 
  however, 
  certain 
  marked 
  deficiencies 
  in 
  the 
  Keisley 
  Limestone 
  

   fauna 
  when 
  we 
  compare 
  it 
  with 
  any 
  part 
  of 
  the 
  Upper 
  Bala. 
  Thus 
  

   the 
  genus 
  Trinucleus 
  is 
  completely 
  wanting, 
  though 
  Tr. 
  seticornis 
  

   is 
  a 
  characteristic 
  trilobite 
  of 
  the 
  whole 
  Upper 
  Bala 
  throughout 
  

   England 
  and 
  Wales. 
  The 
  two 
  typically 
  Ashgill 
  Shale 
  brachiopods, 
  

   namely, 
  Orthis 
  protensa 
  and 
  JStrophomena 
  siluriana, 
  are 
  also 
  con- 
  

   spicuous 
  by 
  their 
  absence. 
  The 
  genus 
  Phacops 
  is 
  completely 
  absent 
  

   from 
  Keisley, 
  so 
  far 
  as 
  is 
  known, 
  though 
  this 
  genus 
  is 
  very 
  rich 
  

   in 
  species 
  and 
  individuals 
  throughout 
  the 
  Middle 
  and 
  Upper 
  Bala 
  

   elsewhere. 
  

  

  The 
  affinities 
  of 
  the 
  Keisley 
  Limestone 
  fauna 
  with 
  that 
  of 
  the 
  

   Slade 
  Beds 
  and 
  Hirnant 
  Limestone 
  are 
  too 
  remote 
  to 
  necessitate 
  

   entering 
  into 
  the 
  question 
  here. 
  

  

  Full 
  weight 
  must 
  be 
  given 
  to 
  the 
  large 
  number 
  of 
  peculiar 
  

   species 
  found 
  in 
  the 
  Keisley 
  Limestone. 
  Thus, 
  of 
  its 
  well-deter- 
  

   mined 
  species, 
  omitting 
  all 
  those 
  about 
  which 
  there 
  is 
  any 
  doubt, 
  

   11 
  are 
  absolutely 
  peculiar 
  to 
  it, 
  and 
  14 
  others 
  are 
  nowhere 
  else 
  

   found 
  in 
  the 
  United 
  Kingdom 
  except 
  in 
  the 
  Kildare 
  Limestone. 
  

  

  