﻿Vol. 
  53.] 
  PA 
  UNA 
  OF 
  THE 
  KEISLEY 
  LIMESTONE. 
  89 
  

  

  It 
  will 
  be 
  seen 
  on 
  examining 
  the 
  list 
  of 
  fossils 
  tabulated 
  on 
  p. 
  85 
  

   that, 
  out 
  of 
  the 
  total 
  number 
  of 
  40 
  species 
  of 
  trilobites 
  in 
  the 
  

   Keisley 
  Limestone, 
  20 
  are 
  definitely 
  known 
  to 
  occur 
  in 
  the 
  Kildare 
  

   Limestone, 
  and 
  6 
  others 
  are 
  doubtfully 
  recorded. 
  

  

  The 
  following 
  species 
  also, 
  so 
  far 
  as 
  is 
  known, 
  are 
  absolutely 
  

   peculiar 
  to 
  these 
  two 
  limestones 
  : 
  — 
  Oheirurus 
  keisley 
  ensis, 
  Ch. 
  can- 
  

   crurus, 
  Sphcereocochus 
  latirugatus, 
  Lichas 
  bulbiceps, 
  Tiresias 
  insculptus, 
  

   Cyphaspis 
  (Tornquistia) 
  Nicholsoni, 
  and 
  CypTioniscus 
  socialis. 
  

  

  In 
  the 
  Leptcena-Limestone 
  10 
  or 
  perhaps 
  12 
  of 
  the 
  Keisley 
  

   species 
  are 
  found, 
  and 
  in 
  the 
  Borkholm 
  and 
  Lyckholm 
  zones 
  3 
  (or 
  4) 
  

   and 
  6 
  have 
  respectively 
  been 
  recorded. 
  Only 
  a 
  very 
  poor 
  list 
  of 
  the 
  

   fauna 
  .of 
  the 
  Borkholm 
  zone 
  is 
  obtainable, 
  1 
  or 
  probably 
  the 
  number 
  

   of 
  common 
  species 
  would 
  have 
  to 
  be 
  increased. 
  Moreover, 
  if 
  we 
  

   take 
  into 
  account 
  the 
  closely-allied 
  but 
  not 
  identical 
  species 
  of 
  

   these 
  beds, 
  the 
  similarity 
  of 
  the 
  trilobitic 
  faunas 
  is 
  still 
  more 
  marked. 
  

   Thus 
  Cheirurus 
  bimucronatus 
  and 
  Ch. 
  Tceisleyensis 
  are 
  allied 
  to 
  

   Ch. 
  insignis 
  and 
  Ch. 
  speciosus 
  of 
  the 
  Leptcena 
  -Limestone 
  ; 
  Ch. 
  

   (Ps.) 
  subquadratus 
  to 
  Ch. 
  (Ps.) 
  Roemeri 
  of 
  the 
  Borkholm 
  and 
  

   Lyckholm 
  zones 
  ; 
  Lichas 
  bifurcatus 
  to 
  L. 
  margaritifer 
  of 
  the 
  

   Leptama-Limestone 
  and 
  Borkholm 
  zone 
  ; 
  Acidaspis 
  convexa 
  to 
  

   A. 
  evoluta 
  of 
  the 
  Leptama-lAvaestoine, 
  ; 
  and 
  Illcenus 
  Bowmani 
  to 
  

   /. 
  Linnarssoni, 
  of 
  the 
  Leptama-IAmestoTie 
  and 
  the 
  Borkholm 
  and 
  

   Lyckholm 
  zones. 
  2 
  

  

  The 
  occurrence 
  of 
  many 
  peculiar 
  species 
  of 
  trilobites 
  is 
  very 
  

   noticeable. 
  Cheirurus 
  {Pseudosphcerexochus) 
  conformis 
  occurs 
  in 
  the 
  

   above-mentioned 
  beds 
  in 
  each 
  area, 
  and 
  it 
  might 
  well 
  be 
  taken 
  as 
  

   the 
  zone-fossil 
  of 
  this 
  horizon. 
  

  

  The 
  following 
  species 
  which 
  are 
  found 
  at 
  Keisley 
  also 
  are 
  markedly 
  

   characteristic 
  of, 
  or 
  limited 
  to, 
  the 
  Z<^cma-Limestone, 
  and 
  therefore 
  

   deserve 
  special 
  notice: 
  — 
  Cheirurus 
  glaber,Ch. 
  (Pseudosphcereocochus) 
  

   conformis, 
  Sphcerocoryphe 
  granulaia 
  (? 
  Keisley), 
  liar 
  pes 
  Wegelini, 
  

   H. 
  costatus 
  (? 
  Keisley), 
  Homalonotusl 
  punctillosus, 
  Ulamus 
  fallax, 
  

   and 
  I. 
  Roemeri. 
  

  

  The 
  following 
  species 
  have 
  been 
  so 
  far 
  found 
  only 
  at 
  Keisley 
  ; 
  

   although 
  two 
  of 
  them 
  are 
  doubtfully 
  recorded 
  from 
  Kildare 
  : 
  — 
  

  

  Cheirurus 
  (Pseudosphcerexochus) 
  subquadratus 
  (? 
  Kildare), 
  Lichas 
  

   bifurcatus 
  (? 
  Kildare), 
  Cyphaspis 
  ? 
  Uarknessi, 
  Ampyx 
  binodulosus, 
  

   Acidaspis 
  convexa, 
  and 
  Illcenus 
  galeatus. 
  

  

  Turning 
  now 
  to 
  the 
  question 
  of 
  the 
  degree 
  of 
  relationship 
  of 
  the 
  

   trilobitic 
  fauna 
  of 
  Keisley 
  to 
  that 
  of 
  the 
  Middle 
  and 
  Upper 
  Bala 
  of 
  

   Great 
  Britain, 
  we 
  find 
  the 
  following 
  species 
  occurring 
  in 
  Middle 
  

   Bala 
  rocks 
  : 
  — 
  Cheirurus 
  bimucronatus, 
  Ch. 
  clavifrons, 
  Dalm. 
  ?, 
  

  

  1 
  Schmidt, 
  * 
  Rev. 
  ostbalt. 
  Silur. 
  Trilob./ 
  pt. 
  i. 
  Mem. 
  Acad. 
  Imp. 
  des 
  Sci. 
  

   St. 
  Petersbourg, 
  ser. 
  7, 
  vol. 
  xxx. 
  (1881) 
  no. 
  I, 
  p. 
  38 
  ; 
  and 
  Quart. 
  Journ. 
  Geol. 
  

   Soc. 
  vol. 
  xxxviii. 
  (1882) 
  p. 
  514. 
  

  

  2 
  Several 
  of 
  the 
  Kildare 
  trilobites, 
  not 
  hitherto 
  found 
  at 
  Keisley, 
  occur 
  in 
  

   Stage 
  F 
  of 
  the 
  Baltic 
  provinces, 
  thus 
  linking 
  these 
  widely-separated 
  beds 
  more 
  

   closely 
  together; 
  see 
  S. 
  H. 
  Reynolds 
  & 
  C. 
  I. 
  Gardiner 
  on 
  'The 
  Kildare 
  

   Inlier/ 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  lii. 
  (1896) 
  p. 
  587. 
  

  

  