﻿Yol. 
  53.] 
  FAUNA 
  OP 
  THE 
  KEISLEY 
  LIMESTONE. 
  93 
  

  

  Platyceras 
  cornutum. 
  Of 
  the 
  others, 
  Holopea 
  concinna 
  and 
  H. 
  stria- 
  

   tella 
  are 
  typically 
  Bala 
  forms. 
  

  

  Loxonema 
  striatissimum, 
  Euomphalus 
  subsulcatus, 
  Holopea 
  con- 
  

   cinna, 
  Gyclonema 
  rupestre, 
  and 
  C. 
  sulciferum 
  are 
  found 
  also 
  in- 
  

   the 
  Kildare 
  Limestone. 
  Loxonema 
  striatissimum 
  is 
  confined 
  to 
  the 
  

   Keisley 
  and 
  Kildare 
  Limestones. 
  Eunema 
  carinatum, 
  Euomphalus 
  

   obtusangulus, 
  and 
  E. 
  nitidulus 
  are 
  Leptcena-LimQstonG 
  species. 
  

   Cyclonema 
  rupestre 
  and 
  Pleurotomaria 
  notabilis 
  occur 
  in 
  Stage 
  Y 
  

   of 
  the 
  Baltic 
  provinces 
  of 
  Russia. 
  

  

  We 
  thus 
  see 
  that 
  the 
  gasteropoda 
  of 
  the 
  Keisley 
  Limestone 
  

   support 
  the 
  conclusions 
  derived 
  from 
  a 
  study 
  of 
  the 
  brachiopoda 
  

   and 
  Crustacea 
  as 
  regards 
  the 
  affinities 
  of 
  the 
  fauna. 
  

  

  The 
  pteropoda 
  and 
  lamellibranchiata 
  are 
  too 
  indefinite 
  to 
  help 
  us. 
  

  

  VI. 
  Echinodermata. 
  — 
  The 
  only 
  determinable 
  form 
  is 
  a 
  species 
  

   (Sphceronites 
  pyriformis) 
  which 
  occurs 
  at 
  Kildare 
  and 
  in 
  the 
  tipper 
  

   Bala 
  of 
  B/hiwlas. 
  It 
  is 
  also 
  noticeable 
  that 
  this 
  genus 
  is 
  particularly 
  

   abundant 
  in 
  the 
  Leptcena-Limestone, 
  being 
  there 
  represented 
  by 
  4 
  

   species. 
  1 
  

  

  VII. 
  Actinozoa. 
  — 
  Of 
  the 
  Actinozoa 
  Streptelasma 
  europceum 
  and 
  

   Stenopora 
  fibrosa, 
  with 
  some 
  indeterminable 
  zaphrentoid 
  corals, 
  are 
  

   the 
  commonest 
  forms 
  at 
  Keisley. 
  But 
  corals 
  are 
  decidedly 
  scarce. 
  

  

  Three 
  species 
  — 
  Halysites 
  catenularia, 
  Stenopora 
  fibrosa, 
  and 
  

   Favosites 
  alveolaris 
  — 
  occur 
  at 
  Kildare. 
  

  

  Halysites 
  catenularia 
  and 
  Heliolites 
  dubia 
  are 
  found 
  in 
  the 
  

   Leptcena-Limestone 
  and 
  in 
  the 
  Lyckholm 
  zone, 
  with 
  the 
  addition 
  

   of 
  Streptelasma 
  europceum, 
  which 
  also 
  occurs 
  in 
  the 
  Borkholm 
  zone. 
  

  

  In 
  Great 
  Britain 
  Halysites 
  catenularia 
  ranges 
  from 
  the 
  Llandeilo 
  

   formation 
  to 
  the 
  Ludlow, 
  Stenopora 
  fibrosa 
  occurs 
  all 
  through 
  the 
  

   Bala, 
  and 
  Streptelasma 
  europceum 
  and 
  Prasopora 
  Grayce 
  are 
  found 
  

   in 
  the 
  Craighead 
  Limestone 
  of 
  Llandeilo 
  age. 
  

  

  Pal^ontological 
  Evidence 
  of 
  the 
  Age 
  of 
  the 
  Keisley 
  Limestone,, 
  

  

  After 
  removing 
  from 
  the 
  list 
  of 
  fossils 
  all 
  those 
  species 
  which 
  are 
  

   either 
  peculiar 
  to 
  the 
  Keisley 
  Limestone, 
  or 
  are 
  found 
  in 
  no 
  other 
  

   bed 
  in 
  the 
  British 
  Isles 
  save 
  the 
  Chair 
  of 
  Kildare 
  Limestone, 
  and 
  

   in 
  addition 
  all 
  the 
  doubtful 
  species, 
  we 
  find 
  that 
  there 
  are 
  16 
  which 
  

   occur 
  in 
  the 
  Lower 
  Bala 
  beds, 
  28 
  in 
  the 
  Middle 
  Bala, 
  20 
  in 
  the 
  

   Upper 
  Bala, 
  and 
  21 
  in 
  the 
  Silurian. 
  But, 
  as 
  the 
  following 
  list 
  

   shows, 
  some 
  of 
  these 
  are 
  species 
  with 
  a 
  great 
  vertical 
  range, 
  and 
  

   therefore 
  ought 
  to 
  be 
  left 
  out 
  of 
  the 
  argument. 
  After 
  their 
  

   removal 
  we 
  find 
  that 
  there 
  are 
  8 
  or 
  9 
  characteristically 
  Middle 
  Bala 
  

   species, 
  3 
  or 
  4 
  Upper 
  Bala 
  species, 
  and 
  3 
  Silurian 
  species. 
  A 
  

   mistake 
  against 
  which 
  we 
  must 
  guard 
  ourselves 
  is 
  to 
  lay 
  too 
  little 
  

   stress 
  on 
  the 
  occurrence 
  of 
  some 
  species 
  belonging 
  to 
  the 
  fauna 
  of 
  a 
  

   bed 
  which 
  is 
  poor 
  in 
  organic 
  remains, 
  or 
  which 
  has 
  been 
  insuffi- 
  

   ciently 
  worked 
  out 
  from 
  a 
  palaeontological 
  point 
  of 
  view. 
  We 
  may, 
  

   I 
  think, 
  safely 
  consider 
  that 
  the 
  Middle 
  Bala 
  and 
  most 
  of 
  the 
  

   Silurian 
  have 
  had 
  their 
  organic 
  contents 
  investigated 
  very 
  fully, 
  

  

  1 
  ' 
  List 
  of 
  the 
  Fossil 
  Faunas 
  of 
  Sweden. 
  I. 
  — 
  Cambrian 
  and 
  Lower 
  Silurian 
  ' 
  

   Stockholm, 
  1888. 
  

  

  