﻿Vol. 
  53.] 
  FAUNA 
  OF 
  THE 
  KEISLEZ 
  LIMESTONE. 
  75 
  

  

  dental 
  plates 
  ; 
  and 
  a 
  long, 
  low, 
  median 
  septum 
  or 
  ridge 
  extends 
  for 
  

   about 
  two-thirds 
  of 
  the 
  length 
  of 
  the 
  brachial 
  valve. 
  

  

  A 
  brachidium 
  with 
  spiral 
  cones 
  of 
  the 
  type 
  of 
  Dayia 
  is 
  present, 
  

   but 
  its 
  details 
  have 
  not 
  been 
  made 
  out, 
  owing 
  to 
  lack 
  of 
  material 
  on 
  

   which 
  to 
  experiment. 
  

  

  millim. 
  

  

  Length 
  of 
  shell 
  8\5 
  

  

  Breadth 
  „ 
  8'0 
  

  

  Affinities. 
  — 
  The 
  extraordinarily 
  close 
  external 
  resemblance 
  of 
  

   this 
  species 
  to 
  Emmons's 
  Cyclospira 
  bisulcata 
  1 
  of 
  the 
  Trenton 
  Lime- 
  

   stone 
  led 
  me 
  at 
  first 
  to 
  the 
  view 
  that 
  it 
  must 
  belong 
  to 
  the 
  same 
  

   genus. 
  With 
  the 
  exception 
  of 
  the 
  absence 
  of 
  the 
  median 
  fold 
  in 
  

   the 
  sinus 
  of 
  the 
  brachial 
  valve, 
  the 
  resemblance 
  appears 
  to 
  be 
  com- 
  

   plete. 
  Eut 
  on 
  developing 
  the 
  interior 
  of 
  the 
  shell 
  I 
  have 
  been 
  able 
  

   to 
  demonstrate 
  that 
  the 
  brachidium 
  is 
  of 
  the 
  type 
  of 
  Dayia 
  navicula, 
  

   which 
  is 
  entirely 
  different 
  from 
  the 
  American 
  genus 
  Cyclospira, 
  as 
  

   Hall 
  & 
  Clarke 
  have 
  recently 
  shown. 
  3 
  

  

  I 
  do 
  not 
  know 
  whether 
  Tornquist's 
  species 
  Dayia 
  pentagona 
  (MS.) 
  4 
  

   is 
  synonymous, 
  as 
  no 
  description 
  or 
  figure 
  has 
  been 
  published. 
  But 
  

   the 
  latter 
  species 
  is 
  from 
  the 
  Z<?pfoma-Limestone, 
  and 
  I 
  have 
  seen 
  

   specimens 
  of 
  the 
  form 
  which 
  I 
  have 
  above 
  described 
  from 
  the 
  same 
  

   rock. 
  There 
  is 
  a 
  specimen 
  of 
  this 
  shell 
  from 
  the 
  Chair 
  of 
  Kildare 
  

   Limestone, 
  labelled 
  Atrypa 
  navicula 
  (var.), 
  in 
  Sir 
  E. 
  Griffith's 
  

   Collection 
  in 
  the 
  Dublin 
  Museum. 
  

  

  Hyattella 
  Poetlockiana 
  (Davidson). 
  

  

  Davidson 
  described 
  this 
  species 
  more 
  than 
  25 
  years 
  ago 
  from 
  

   the 
  Limestone 
  of 
  the 
  Chair 
  of 
  Kildare, 
  5 
  and 
  subsequently 
  (in 
  his 
  

   Supplement 
  to 
  the 
  Silurian 
  Brachiopoda) 
  from 
  the 
  Upper 
  Llandeilo 
  

   of 
  Balcletchie, 
  Girvan. 
  The 
  external 
  characters 
  of 
  the 
  shell 
  

   were 
  alone 
  given, 
  and 
  it 
  was 
  assigned 
  doubtfully 
  to 
  the 
  genus 
  

   Khynchonella. 
  Lindstrom 
  6 
  placed 
  it 
  in 
  the 
  genus 
  Athyris, 
  but 
  

   does 
  not 
  mention 
  his 
  reasons 
  for 
  so 
  doing. 
  I 
  have 
  been 
  able 
  to 
  

   expose 
  the 
  internal 
  structure 
  with 
  some 
  completeness, 
  and 
  to 
  

   demonstrate 
  the 
  presence 
  of 
  spiral 
  lamellae, 
  necessitating 
  the 
  removal 
  

   of 
  this 
  species 
  both 
  from 
  the 
  genus 
  Bhynchonella 
  and 
  from 
  the 
  

   genus 
  Athyris. 
  

  

  There 
  are 
  two 
  fairly 
  distinct 
  varieties 
  of 
  this 
  species 
  — 
  a 
  long 
  one 
  

   and 
  a 
  broad 
  one. 
  The 
  elongated 
  ovate 
  form 
  is 
  that 
  figured 
  by 
  

   Davidson 
  ; 
  those 
  illustrated 
  by 
  Lindstrom 
  are 
  rather 
  broader 
  and 
  

   more 
  globose, 
  and 
  pass 
  into 
  the 
  transverse 
  or 
  broad 
  variety. 
  Inter- 
  

  

  1 
  « 
  Geol. 
  New 
  York,' 
  Eept. 
  Second 
  Distr. 
  (1842) 
  p. 
  395, 
  fig. 
  4 
  ( 
  Orthis 
  bisulcata) 
  ; 
  

   Hall, 
  ' 
  Pal. 
  N. 
  Y.,' 
  vol. 
  i. 
  (1847) 
  p. 
  139, 
  pi. 
  xxxiii. 
  fig. 
  3 
  (Atrypa 
  bisulcata) 
  ; 
  

   Hall& 
  Clarke, 
  ibid. 
  vol. 
  viii. 
  Brach. 
  pt. 
  ii. 
  (1894) 
  p. 
  146 
  (Cyclospira 
  bisulcata). 
  

  

  2 
  Davidson, 
  ' 
  Mon. 
  Brit. 
  Foss. 
  Brach.,' 
  vol. 
  iii. 
  (1869) 
  p. 
  190, 
  pi. 
  xxii. 
  figs. 
  20- 
  

   23; 
  vol. 
  v. 
  Suppl. 
  Sil. 
  Brach. 
  (1882) 
  p. 
  96, 
  pi. 
  v. 
  figs. 
  1-4. 
  

  

  3 
  ' 
  Pal. 
  N. 
  Y.,' 
  vol. 
  viii. 
  Brach. 
  pt. 
  ii. 
  (1894). 
  

  

  4 
  E. 
  Stolley, 
  'Die 
  cambrischen 
  u. 
  silurischen 
  Geschiebe 
  Schleswig-Holsteins,' 
  

   Archiv 
  fur 
  Anthrop. 
  u. 
  Geol. 
  Schl.-Holst., 
  vol. 
  i. 
  pt. 
  i. 
  (1895) 
  p. 
  88. 
  

  

  5 
  'Mon. 
  Brit. 
  Foss. 
  Brach.,' 
  vol. 
  iii. 
  (1869) 
  p. 
  189, 
  pi. 
  xxiv. 
  figs. 
  23-25;. 
  

   vol. 
  v. 
  Suppl. 
  Sil. 
  Brach. 
  (1882) 
  p. 
  159, 
  pi. 
  x. 
  figs. 
  12-14. 
  

  

  6 
  'Fragm. 
  Silur.' 
  (1880) 
  p. 
  22, 
  pi. 
  xiii. 
  figs. 
  20-22. 
  

  

  