﻿'^°1' 
  53*] 
  FAUXA 
  OF 
  THE 
  KEISLEY 
  LIMESTONE. 
  99 
  

  

  Schmalensee 
  1 
  has 
  expressed 
  the 
  view 
  that 
  the 
  Leptcena-Limestone 
  

   corresponds 
  with 
  the 
  horny 
  Klingkalk 
  immediately 
  above 
  the 
  Tri- 
  

   nucleus-Shales, 
  and 
  Marr 
  2 
  likewise 
  says 
  that 
  the 
  Keisley 
  Limestone 
  

   ma}* 
  be 
  represented 
  by 
  a 
  white 
  horny 
  limestone 
  seen 
  in 
  the 
  stream 
  

   at 
  the 
  Upper 
  Bridge, 
  Skelgill 
  Brook, 
  containing 
  large 
  Ortliocerata 
  

   and 
  occurring 
  immediately 
  below 
  the 
  Staurocephalus-lAmestone. 
  

   Nathorst 
  3 
  illustrates 
  this 
  view 
  of 
  the 
  occurrence 
  of 
  the 
  Leptcena- 
  

   Limestone 
  by 
  a 
  diagram 
  showing 
  the 
  local 
  swelling-out 
  of 
  a 
  thin 
  

   band 
  of 
  limestone 
  into 
  a 
  thick 
  reef-like 
  mass. 
  Ferd. 
  Homer, 
  4 
  on 
  

   palaeontological 
  grounds, 
  adopts 
  the 
  view 
  that 
  the 
  Leptama-lAme- 
  

   stone 
  is 
  at 
  the 
  upper 
  limit 
  of 
  the 
  Lower 
  Silurian 
  [ 
  = 
  Ordovician] 
  ; 
  

   and 
  Holm 
  5 
  and 
  Andersson, 
  6 
  more 
  recently, 
  do 
  the 
  same. 
  

  

  It 
  may 
  be 
  noticed 
  here 
  that 
  several 
  of 
  the 
  species 
  limited 
  in 
  

   Sweden 
  to 
  the 
  Lepicena-XAmastone, 
  in 
  England 
  to 
  the 
  Keisley 
  

   Limestone, 
  and 
  in 
  Ireland 
  to 
  the 
  Chair 
  of 
  Kildare 
  Limestone 
  occur 
  

   in 
  the 
  East 
  Baltic 
  provinces, 
  not 
  only 
  in 
  the 
  Borkholm 
  Limestone, 
  

   which 
  Schmidt 
  "' 
  correlates 
  exactly 
  with 
  the 
  Zgpfrma-Limestone, 
  

   but 
  also 
  in 
  the 
  underlying 
  Lyckholm 
  zone. 
  Thus 
  Pseud.osphcerex- 
  

   ochus 
  conformis, 
  Oheirurus 
  cf. 
  glaber, 
  Cybele 
  brevicauda* 
  Harpes 
  

   Wec/elini, 
  Lichas 
  dalecarlicus, 
  Bronteus 
  latieauda, 
  and 
  HeUolites 
  

   dubia 
  are 
  recorded 
  among 
  others 
  by 
  Schmidt 
  9 
  from 
  the 
  Lyckholm 
  

   zone, 
  but 
  in 
  Sweden 
  for 
  the 
  first 
  and 
  only 
  time 
  from 
  the 
  Leptcena- 
  

   Limestone. 
  Schmidt 
  10 
  indeed 
  says 
  that 
  the 
  Lyckholm 
  and 
  Bork- 
  

   holm 
  zones 
  are 
  so 
  closely 
  allied 
  in 
  their 
  faunas 
  that 
  they 
  cannot 
  be 
  

   separated 
  at 
  present 
  as 
  distinct 
  stages. 
  Yet, 
  on 
  the 
  other 
  hand, 
  

   though 
  he 
  considers 
  his 
  Stage 
  F 
  to 
  represent 
  - 
  the 
  British 
  Caradoc 
  

   Sandstone 
  and 
  the 
  Coniston 
  and 
  Craighead 
  Limestones,' 
  it 
  is 
  

   remarkable 
  that 
  so 
  many 
  of 
  its 
  typical 
  species 
  do 
  not 
  occur 
  in 
  

   Britain 
  till 
  the 
  Keisley 
  Limestone, 
  which 
  we 
  have 
  been 
  led 
  to 
  place 
  

   at 
  the 
  base 
  of 
  the 
  Upper 
  Bala 
  — 
  e. 
  g. 
  Pseudosphoereocochus 
  conformis, 
  

   Oheirurus 
  cf. 
  glaber, 
  Illcenus 
  Rcemeri, 
  I. 
  ccecus, 
  Harpes 
  Wec/dini, 
  

   Plectambonites 
  Schmidti, 
  Cyclonema 
  rupestre, 
  Pleurotomarianotabilis. 
  

   It 
  is 
  also 
  noticeable 
  that 
  several 
  Keisley 
  Limestone 
  species 
  are 
  

   very 
  closely 
  allied 
  to 
  forms 
  not 
  occurring 
  in 
  lower 
  beds 
  in 
  Britain, 
  

   but 
  in 
  lower 
  beds 
  in 
  Scandinavia. 
  Of 
  these 
  the 
  following 
  are 
  

   examples 
  : 
  — 
  Oheirurus 
  Jceisleyensis, 
  which 
  is 
  allied 
  to 
  Oh. 
  subulatus- 
  

   of 
  the 
  Trinucleus-Schists, 
  and 
  Oyphaspis 
  Nicholsoni, 
  which 
  so 
  much 
  

   resembles 
  Trilobites 
  Iriradiatus 
  of 
  the 
  same 
  beds. 
  

  

  1 
  ' 
  Om 
  Leptaenak. 
  Plats 
  i 
  Silur. 
  Lag.' 
  Geol. 
  Foren. 
  i 
  Stockh. 
  Forhandl. 
  no. 
  89 
  y 
  

   vol. 
  vii. 
  (18^4), 
  pt. 
  5, 
  p. 
  280; 
  ibid. 
  no. 
  146, 
  vol. 
  xiv. 
  (1892), 
  pt. 
  6, 
  p. 
  497. 
  

  

  2 
  Geol. 
  Mag. 
  1892, 
  p. 
  97. 
  

  

  3 
  ' 
  Nagr. 
  o. 
  o. 
  Slipsandst. 
  i. 
  Dal.' 
  Geol. 
  Foren. 
  i 
  Stockh. 
  Forhandl. 
  no. 
  93, 
  

   vol. 
  vii. 
  (1884) 
  pt. 
  9, 
  p. 
  559. 
  

  

  4 
  ' 
  Lethaea 
  Erratica,' 
  Palaont. 
  Abhandl. 
  Berlin, 
  vol. 
  ii. 
  (1885) 
  pt. 
  v. 
  p. 
  72. 
  

  

  5 
  Sveriges 
  Geol. 
  Undersokn. 
  ser. 
  c, 
  no. 
  115, 
  pp. 
  14, 
  15, 
  Stockholm, 
  1890. 
  

  

  6 
  Ofvers. 
  K. 
  Sv. 
  Vet. 
  Akad. 
  Forhandl. 
  50 
  Arg. 
  p. 
  571, 
  Stockholm. 
  

  

  7 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xxxviii. 
  (1882) 
  p. 
  514. 
  

  

  8 
  This 
  species 
  is 
  stated 
  by 
  Schmidt 
  to 
  occur 
  also 
  in 
  his 
  Stage 
  E. 
  

  

  9 
  'Kev. 
  ostbalt. 
  silur. 
  Trilob.,' 
  pt. 
  i. 
  Mem. 
  Acad. 
  Imp. 
  des 
  Sci. 
  St. 
  Petersbourg, 
  

   ser. 
  7, 
  vol. 
  xxx. 
  (1881) 
  no. 
  1. 
  

  

  10 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xxxviii. 
  (1882) 
  p. 
  514. 
  

  

  h2 
  

  

  