﻿Yol. 
  53.] 
  FAUNA 
  OF 
  THE 
  KEISLEY 
  LIMESTONE. 
  77 
  

  

  Affinities. 
  — 
  This 
  species 
  I 
  would 
  assign 
  to 
  the 
  genus 
  Hyattella,. 
  

   which 
  Hall 
  & 
  Clarke 
  have 
  recently 
  established 
  {loc. 
  cit.). 
  In 
  ex- 
  

   ternal 
  characters 
  H. 
  Porilochiana 
  agrees 
  very 
  closely 
  with 
  Conrad's 
  

   H. 
  congesta 
  from 
  the 
  Clinton 
  Group, 
  and 
  in 
  its 
  internal 
  features 
  the 
  

   loose 
  spiral 
  coils, 
  with 
  their 
  few 
  volutions, 
  position, 
  and 
  shape, 
  the 
  

   course 
  of 
  the 
  primary 
  lamellae, 
  the 
  shape 
  of 
  the 
  hinge-plate, 
  with 
  

   its 
  narrow 
  median 
  cleft 
  and 
  short 
  crura, 
  the 
  deep 
  and 
  striated 
  

   pedicle-cavity 
  in 
  the 
  pedicle-valve, 
  with 
  strong 
  short 
  dental 
  plates, 
  

   and 
  the 
  loop 
  and 
  process, 
  so 
  far 
  as 
  can 
  be 
  made 
  out, 
  are 
  essentially 
  

   similar. 
  The 
  chief 
  points 
  of 
  difference 
  are 
  the 
  presence 
  of 
  the 
  

   short 
  median 
  septum 
  in 
  the 
  brachial 
  valve, 
  and 
  the 
  greater 
  length 
  

   of 
  the 
  process 
  of 
  the 
  loop. 
  

  

  This 
  species 
  (H. 
  Portlockiana) 
  is 
  found 
  in 
  the 
  Lej)tama 
  -Limestone- 
  

   in 
  tolerable 
  abundance. 
  

  

  POLTZOA. 
  

  

  Ptilodictya 
  costellata, 
  M'Coy 
  ? 
  

  

  Ptilodictta 
  eecta, 
  Hall 
  ? 
  

  

  These 
  two 
  species 
  are 
  doubtfully 
  recorded 
  from 
  Keisley. 
  

  

  Penestella 
  assimilis, 
  Lonsdale. 
  

   Not 
  very 
  common. 
  

  

  MOLLUSCA. 
  

   Cephalopoda. 
  

   Orthoceras 
  cf. 
  scabridum 
  (Ang.). 
  

  

  Some 
  fragmentary 
  specimens 
  from 
  Keisley 
  resemble 
  this 
  species 
  

   of 
  Angelin's 
  * 
  in 
  their 
  cylindrical 
  shape, 
  with 
  a 
  very 
  slow 
  rate 
  of 
  

   tapering, 
  in 
  the 
  great 
  distance 
  apart 
  of 
  the 
  septa 
  (i. 
  e. 
  1 
  to 
  1^ 
  

   the 
  diameter 
  of 
  the 
  shell), 
  in 
  the 
  deep 
  cup-shape 
  of 
  the 
  septa, 
  in 
  

   the 
  central 
  siphuncle, 
  and, 
  as 
  far 
  as 
  can 
  be 
  seen, 
  in 
  the 
  ornamen- 
  

   tation 
  of 
  the 
  surface 
  of 
  the 
  shell. 
  

  

  0. 
  scabridum, 
  in 
  Sweden, 
  is 
  found 
  in 
  the 
  Oi*t7ioceras-Limestone. 
  

  

  Poord 
  2 
  mentions 
  that, 
  in 
  addition 
  to 
  0. 
  cf. 
  elongatocinctum 
  

   (PortL), 
  another 
  species 
  occurs 
  in 
  the 
  Keisley 
  Limestone, 
  and 
  he 
  

   may 
  be 
  referring 
  to 
  0. 
  cf. 
  scabridum. 
  

  

  Orthoceras 
  cf. 
  elongatocinctum 
  (Port!.). 
  

  

  Foord 
  (loc. 
  cit.) 
  describes 
  this 
  species 
  from 
  Keisley, 
  where 
  it 
  is 
  the 
  

   commonest 
  Orthoceras, 
  and 
  in 
  some 
  parts 
  of 
  the 
  limestone 
  occurs 
  in 
  

   abundance 
  almost 
  to 
  the 
  exclusion 
  of 
  other 
  fossils. 
  

  

  1 
  Lindstrom, 
  * 
  Pragm. 
  Silur.' 
  (1880) 
  p. 
  4, 
  pi. 
  iv. 
  figs. 
  6-9 
  & 
  pi. 
  vii. 
  figs. 
  8-10. 
  

  

  2 
  Quart. 
  Journ. 
  Geol. 
  Soc. 
  vol. 
  xlvii. 
  (1891) 
  p. 
  526. 
  

  

  