﻿$2 
  ME. 
  P. 
  E. 
  COWPEE 
  SEED 
  ON 
  THE 
  [Feb. 
  1 
  897, 
  

  

  A 
  very 
  considerable 
  number 
  are 
  found 
  in 
  British 
  Silurian 
  beds. 
  

  

  The 
  following 
  is 
  a 
  list 
  of 
  these 
  species 
  : 
  — 
  

  

  Orthis 
  Actonice, 
  0. 
  biforata, 
  0. 
  biloba, 
  0. 
  elegantula, 
  0. 
  calli- 
  

   gramma, 
  0. 
  testuclinaria, 
  0. 
  vespertilio, 
  Strophomena 
  antiquata, 
  

   JStr. 
  corrugatella, 
  Rafinesqwina 
  eocpansa, 
  Plectambonites 
  transversalis, 
  

   PI. 
  quinquecostata, 
  Leptcena 
  rhomboidalis, 
  Triplecia 
  insularis, 
  

   JStreptis 
  monilifera, 
  and 
  Atrypa 
  marginalis. 
  

  

  Thus 
  16 
  species, 
  or 
  over 
  44 
  °/ 
  , 
  occur 
  in 
  the 
  Silurian. 
  But 
  none 
  

   of 
  these 
  are 
  characteristically 
  Silurian 
  forms, 
  1 
  and 
  all 
  of 
  them 
  are 
  

   known 
  from 
  Bala 
  Beds. 
  Owing, 
  therefore, 
  to 
  their 
  long 
  range, 
  they 
  

   are 
  of 
  comparatively 
  little 
  zonal 
  importance, 
  and 
  cannot 
  justly 
  be 
  

   used 
  in 
  support 
  of 
  the 
  argument 
  for 
  the 
  Silurian 
  facies 
  of 
  the 
  fauna. 
  

   It 
  is 
  also 
  specially 
  noteworthy 
  that 
  such 
  typically 
  Silurian 
  genera 
  

   •as 
  Stricklandinia 
  and 
  Pentamerus 
  (and 
  its 
  subgenera 
  or 
  allied 
  

   genera) 
  are 
  conspicuous 
  by 
  their 
  absence. 
  There 
  are, 
  moreover, 
  no 
  

   species 
  of 
  Spirifer 
  such 
  as 
  we 
  should 
  expect 
  to 
  find 
  in 
  Silurian 
  strata. 
  

  

  In 
  the 
  Z<?p£cma-Lime3tone, 
  indeed, 
  Meristella 
  ? 
  crassa 
  is 
  found, 
  

   but 
  this 
  species 
  marks 
  the 
  conglomerate 
  at 
  the 
  top 
  of 
  the 
  Ashgill 
  

   Shales 
  in 
  Britain, 
  and 
  this 
  bed 
  is 
  on 
  the 
  border-line 
  between 
  the 
  

   Silurian 
  and 
  Ordovician. 
  

  

  On 
  the 
  whole 
  we 
  must 
  therefore 
  say 
  that 
  the 
  brachiopoda 
  of 
  the 
  

   Keisley 
  Limestone 
  are 
  an 
  assemblage 
  of 
  species 
  of 
  a 
  Middle 
  and 
  

   Upper 
  Ordovician 
  stamp, 
  but 
  that 
  this 
  assemblage 
  possesses 
  a 
  

   certain 
  uniqueness 
  which 
  can 
  be 
  most 
  closely 
  paralleled 
  by 
  that 
  of 
  

   the 
  Kildare 
  and 
  Leptcena-Limestones, 
  as 
  in 
  the 
  case 
  of 
  the 
  trilobitic 
  

   fauna. 
  

  

  IV. 
  Poltzoa. 
  — 
  Members 
  of 
  this 
  group 
  appear 
  very 
  rare 
  at 
  

   Keisley, 
  whereas 
  at 
  Kildare 
  and 
  in 
  the 
  Dalecarlian 
  and 
  Russian 
  

   assumed 
  equivalent 
  formations 
  they 
  are 
  very 
  common. 
  In 
  fact, 
  the 
  

   Leptama-Limestone 
  has 
  the 
  alternative 
  name 
  ' 
  Fenestellenkalk, 
  2 
  ' 
  

   and 
  a 
  long 
  list 
  of 
  polyzoa 
  is 
  known 
  from 
  Stage 
  F 
  of 
  Schmidt. 
  

  

  All 
  the 
  Keisley 
  polyzoa 
  that 
  I 
  have 
  seen 
  are 
  very 
  imperfect 
  

   and 
  fragmentary 
  specimens 
  ; 
  all 
  the 
  species 
  are 
  doubtfully 
  identified, 
  

   but 
  two 
  of 
  these 
  (Ptilodictya 
  recta 
  and 
  Fenestella 
  assimilis) 
  occur 
  

   in 
  the 
  Kildare 
  Limestone, 
  and 
  the 
  third 
  (Pt. 
  costellata) 
  is 
  a 
  Bala 
  

   form. 
  There 
  is 
  no 
  Silurian 
  species 
  among 
  them. 
  JNot 
  one 
  of 
  the 
  

   three 
  species 
  is 
  recorded 
  from 
  the 
  Leptcena-Limestone 
  or 
  Stage 
  F 
  

   except 
  Pt. 
  costellata, 
  which 
  occurs 
  in 
  the 
  Borkholm 
  zone. 
  

  

  V. 
  MoLLirscA. 
  — 
  Of 
  the 
  mollusca 
  the 
  cephalopoda 
  are 
  by 
  far 
  the 
  

   most 
  abundant 
  group 
  in 
  the 
  Keisley 
  Limestone, 
  but 
  there 
  appear 
  to 
  

   be 
  only 
  the 
  two 
  species 
  of 
  Orthoceras 
  as 
  the 
  representatives 
  of 
  the 
  

   group. 
  Neither 
  of 
  these 
  throw 
  any 
  light 
  on 
  the 
  horizon 
  of 
  the 
  

   limestone. 
  

  

  The 
  gasteropoda 
  are 
  represented 
  by 
  a 
  dozen 
  or 
  more 
  species 
  

   belonging 
  to 
  9 
  genera, 
  but 
  they 
  are 
  by 
  no 
  means 
  common. 
  The 
  

   most 
  abundant 
  form 
  is 
  Looconema 
  striatissimum, 
  which 
  shows 
  

   close 
  affinity 
  with 
  Silurian 
  species. 
  The 
  only 
  other 
  species 
  

   suggesting 
  Silurian 
  affinity 
  is 
  the 
  form 
  compared 
  with 
  Hisinger's 
  

  

  1 
  Except 
  Atrypa" 
  marginalis 
  and 
  Orthis 
  biloba. 
  

  

  2 
  Eemele, 
  Zeitschr. 
  d. 
  Deutsch. 
  geol. 
  Gesellsch. 
  vol. 
  xxxii. 
  (1880) 
  p. 
  645, 
  & 
  

   vol. 
  xxxiv. 
  (1882) 
  p. 
  651. 
  

  

  