﻿106 
  THE 
  FAUNA 
  OF 
  THE 
  KEISLEY 
  LIMESTONE. 
  [Feb. 
  1 
  897, 
  

  

  speaker) 
  had 
  attempted 
  to 
  define 
  the 
  base 
  of 
  the 
  Upper 
  Bala 
  in 
  

   Britain 
  upon 
  palaeontological 
  grounds. 
  The 
  Author 
  was 
  mistaken 
  

   in 
  saying 
  that 
  the 
  speaker 
  considered 
  the 
  Keisley 
  Limestone 
  a 
  local 
  

   development 
  ; 
  what 
  he 
  did 
  think 
  was 
  that 
  its 
  peculiar 
  features 
  at 
  

   Keisley 
  were 
  due 
  to 
  subsequent 
  earth-movement. 
  Finally, 
  he 
  

   disputed 
  the 
  statement 
  that 
  Trinucleus 
  seticornis 
  was 
  a 
  characteristic 
  

   Upper 
  Bala 
  fossil. 
  The 
  type 
  (in 
  Sweden) 
  came 
  from 
  Middle 
  Bala 
  

   beds 
  ; 
  it 
  was 
  very 
  common 
  in 
  Middle 
  Bala 
  beds 
  in 
  Britain, 
  and, 
  so 
  

   far 
  as 
  the 
  speaker's 
  experience 
  went, 
  rare 
  in 
  Upper 
  Bala 
  beds. 
  

  

  Dr. 
  G. 
  J. 
  Hotde 
  enquired 
  of 
  the 
  Author 
  whether 
  he 
  had 
  compared 
  

   the 
  fauna 
  of 
  the 
  Keisley 
  Limestone 
  with 
  that 
  of 
  the 
  Hudson 
  River 
  

   formation 
  of 
  Eastern 
  North 
  America, 
  and 
  more 
  particularly 
  with 
  

   that 
  shown 
  on 
  the 
  Island 
  of 
  Anticosti. 
  Judging 
  from 
  the 
  specimens 
  

   exhibited, 
  it 
  seemed 
  to 
  the 
  speaker 
  that 
  there 
  were 
  several 
  species 
  

   common 
  to 
  these 
  widely-separated 
  areas. 
  

  

  The 
  Author, 
  in 
  replying 
  to 
  Mr. 
  Marr, 
  who 
  objected 
  to 
  the 
  use 
  

   of 
  percentages 
  in 
  determining 
  the 
  relations 
  of 
  faunas, 
  held 
  that 
  

   percentages 
  were 
  merely 
  a 
  concise 
  way 
  of 
  stating 
  ascertained 
  facts, 
  

   and 
  were 
  only 
  misleading 
  when 
  the 
  special 
  conditions 
  and 
  modifying 
  

   circumstances 
  of 
  each 
  case 
  were 
  left 
  out 
  of 
  account. 
  Mr. 
  Marr 
  also 
  

   denied 
  that 
  Trinucleus 
  seticornis 
  was 
  specially 
  characteristic 
  of 
  

   Upper 
  Bala 
  beds, 
  though 
  some 
  years 
  ago 
  he 
  had 
  called 
  the 
  Upper 
  

   Bala 
  beds 
  of 
  the 
  Haverfordwest 
  area 
  after 
  that 
  fossil. 
  From 
  the 
  

   examination 
  of 
  a 
  very 
  large 
  number 
  of 
  so-called 
  examples 
  of 
  this 
  

   species 
  from 
  the 
  Middle 
  Bala, 
  the 
  Author 
  could 
  positively 
  state 
  

   that 
  the 
  great 
  majority 
  of 
  them 
  were 
  quite 
  distinct 
  from 
  the 
  

   common 
  form 
  which 
  bears 
  this 
  name 
  in 
  Upper 
  Bala 
  beds. 
  He 
  had 
  

   had 
  no 
  opportunity 
  of 
  comparing 
  the 
  Keisley 
  Limestone 
  fauna 
  with 
  

   that 
  of 
  the 
  Hudson 
  River 
  Group. 
  

  

  