﻿88 
  MR. 
  F. 
  R. 
  COWPEE 
  REED 
  ON 
  THE 
  [Feb. 
  1 
  897, 
  

  

  General 
  Kemarks 
  on 
  the 
  Fauna 
  of 
  the 
  Keisley 
  Limestone. 
  

  

  I. 
  Trilobita. 
  — 
  The 
  Trilobita 
  are 
  unmistakably 
  the 
  predominant 
  

   members 
  of 
  the 
  assemblage 
  of 
  organisms 
  which 
  we 
  meet 
  with 
  in 
  

   the 
  Keisley 
  Limestone. 
  Not 
  only 
  in 
  the 
  number 
  and 
  variety 
  of 
  the 
  

   genera 
  and 
  species 
  do 
  they 
  far 
  exceed 
  other 
  groups, 
  but 
  also 
  in 
  the 
  

   number 
  of 
  individuals. 
  Yet 
  all 
  the 
  genera 
  are 
  not 
  equal 
  in 
  this 
  

   latter 
  respect, 
  nor 
  are 
  the 
  species. 
  The 
  lllceni 
  are 
  the 
  most 
  common 
  

   of 
  all 
  the 
  trilobites, 
  and 
  large 
  slabs 
  covered 
  with 
  the 
  head-shields 
  

   and 
  pygidia 
  of 
  I. 
  Bowmani 
  and 
  its 
  varieties 
  are 
  of 
  frequent 
  occur- 
  

   rence, 
  i". 
  galeatus 
  is 
  the 
  next 
  most 
  common 
  species 
  of 
  Illcenus, 
  

   while 
  I. 
  Boemeri, 
  I. 
  fallaoc, 
  and 
  I. 
  ccecus 
  are 
  very 
  rare. 
  

  

  Next 
  in 
  order 
  of 
  abundance 
  come 
  the 
  genera 
  of 
  Cheiruridae, 
  and 
  

   in 
  species 
  and 
  individuals 
  they 
  hold 
  the 
  same 
  place. 
  The 
  species 
  

   of 
  Pseudosphcerexochus 
  and 
  of 
  Sphcerexochus 
  are 
  represented 
  by 
  

   numerous 
  individuals. 
  The 
  genus 
  Lichas 
  has 
  at 
  least 
  six 
  species 
  

   belonging 
  to 
  it 
  in 
  this 
  rock, 
  but 
  the 
  individuals 
  are 
  not 
  numerous. 
  

   Cyphoniscus 
  socialis 
  is 
  fairly 
  abundant. 
  From 
  the 
  failure 
  of 
  many 
  

   observers 
  and 
  collectors 
  to 
  find 
  such 
  trilobites 
  as 
  Staurocephalus 
  

   Murchisoni, 
  of 
  which 
  I 
  have 
  myself 
  collected 
  at 
  least 
  a 
  dozen 
  

   specimens 
  in 
  a 
  few 
  hours, 
  I 
  believe 
  the 
  occurrence 
  of 
  such 
  forms 
  

   is 
  sporadic 
  or 
  limited 
  to 
  special 
  bands 
  in 
  the 
  rock. 
  It 
  should 
  be 
  

   remembered 
  that 
  the 
  great 
  majority 
  of 
  the 
  fossils 
  recorded 
  have 
  

   been 
  collected 
  from 
  loose 
  blocks 
  in 
  the 
  adjacent 
  stone 
  walls, 
  or 
  

   hammered 
  out 
  of 
  detached 
  masses 
  lying 
  on 
  the 
  surface 
  of 
  the 
  

   ground. 
  Many 
  of 
  those 
  which 
  I 
  found 
  were 
  obtained 
  from 
  the 
  

   remains 
  of 
  an* 
  old 
  lime-kiln 
  close 
  to 
  the 
  large 
  quarry, 
  but 
  others 
  

   were 
  chipped 
  out 
  of 
  the 
  outcropping 
  solid 
  rock. 
  

  

  The 
  peculiar 
  features 
  of 
  the 
  trilobitic 
  fauna 
  are 
  : 
  — 
  (1) 
  The 
  absence 
  

   of 
  the 
  genera 
  Phacops 
  and 
  Trinudeus. 
  Both 
  these 
  genera 
  are 
  so 
  

   abundant 
  in 
  the 
  Bala 
  rocks 
  of 
  all 
  areas, 
  and 
  are 
  represented 
  by 
  

   species 
  so 
  characteristic, 
  that 
  their 
  entire 
  absence 
  is 
  very 
  striking. 
  

   In 
  the 
  Staurocephalus-Liiaestone 
  and 
  Ashgill 
  Shales, 
  as 
  well 
  as 
  

   in 
  the 
  underlying 
  Middle 
  Bala, 
  we 
  find 
  them 
  making 
  a 
  marked 
  

   feature 
  in 
  the 
  fauna. 
  The 
  genera 
  Trinudeus 
  and 
  Phacops 
  are 
  

   practically 
  absent 
  from 
  the 
  Chair 
  of 
  Kildare 
  Limestone 
  1 
  and 
  the 
  

   Leptcena-Limestone. 
  Trinudeus 
  is 
  very 
  rare 
  in 
  the 
  Russian 
  Stage 
  F, 
  2 
  

   and 
  till 
  recently 
  was 
  thought 
  not 
  to 
  occur 
  there. 
  (2) 
  The 
  occurrence 
  

   of 
  certain 
  peculiar 
  genera 
  of 
  very 
  limited 
  range 
  in 
  time 
  and 
  space, 
  

   as, 
  for 
  example, 
  Cyphoniscus 
  and 
  Tiresias. 
  (3) 
  The 
  occurrence 
  of 
  

   many 
  peculiar 
  species 
  limited 
  either 
  entirely 
  to 
  this 
  Keisley 
  bed, 
  or 
  

   to 
  it 
  and 
  the 
  Chair 
  of 
  Kildare 
  Limestone, 
  or 
  to 
  both 
  these 
  beds 
  and 
  

   the 
  Leptcena-IAmestone 
  of 
  Dalecarlia, 
  or 
  to 
  the 
  Keisley 
  and 
  Dale- 
  

   carlian 
  beds, 
  or 
  to 
  one 
  of 
  these 
  beds 
  and 
  Stage 
  F 
  of 
  the 
  East 
  Baltic 
  

   provinces 
  of 
  Russia. 
  

  

  1 
  Quite 
  recently 
  Mr. 
  C. 
  I. 
  Gardiner, 
  F.G.S., 
  has 
  shown 
  me 
  an 
  eye 
  of 
  a 
  

   Phacops 
  and 
  a 
  fragment 
  of 
  a 
  Trinudeus— 
  possibly 
  Tr. 
  seticomis 
  (His.) 
  — 
  from 
  the 
  

   Kildare 
  Limestone 
  ; 
  but 
  these 
  are 
  the 
  only 
  specimens 
  I 
  know. 
  

  

  2 
  Fr. 
  Schmidt, 
  'Kev. 
  ostbalt. 
  Silur. 
  Trilob.,' 
  pt. 
  iv. 
  Mem. 
  Acad. 
  Imp. 
  des 
  

   Sci. 
  St. 
  Petersbourg, 
  ser. 
  7, 
  vol. 
  xlii. 
  (1894) 
  no. 
  5, 
  p. 
  71. 
  

  

  