﻿68 
  G. 
  R. 
  VINE 
  ON 
  THE 
  WENLOCK 
  POLYZOA. 
  

  

  P. 
  interporosa 
  there 
  are 
  none 
  of 
  these 
  spaces 
  : 
  there 
  are 
  single 
  

   rows 
  surrounding 
  each 
  orifice, 
  very 
  rarely 
  more 
  : 
  but 
  occasionally 
  

   the 
  rows 
  are 
  double 
  in 
  some 
  few 
  of 
  the 
  interspaces. 
  Again, 
  noDe 
  

   of 
  the 
  cells 
  of 
  Fistulipora 
  are 
  arranged 
  in 
  series; 
  in 
  the 
  species 
  

   described 
  above 
  they 
  are 
  distinctly 
  serial, 
  either 
  perpendicularly 
  or 
  

   obliquely. 
  

  

  Ptilodictya 
  cosciniformis, 
  ISTich. 
  (Geol. 
  Mag. 
  1875), 
  is 
  the 
  only 
  

   species 
  with 
  which 
  I 
  can 
  compare 
  P. 
  interporosa 
  ; 
  but 
  in 
  size 
  and 
  

   habit 
  the 
  American 
  species 
  is 
  so 
  different 
  from 
  our 
  own, 
  that 
  there 
  

   seems 
  to 
  be 
  no 
  natural 
  affinity 
  between 
  them. 
  Again, 
  the 
  species 
  

   described 
  by 
  me 
  has 
  only 
  four 
  cells 
  to 
  the 
  line 
  ; 
  in 
  Nicholson's 
  species 
  

   six 
  or 
  seven 
  cells, 
  measured 
  diagonally, 
  occupy 
  the 
  same 
  space. 
  And 
  

   although 
  in 
  P. 
  cosciniformis, 
  JN"ich., 
  " 
  the 
  interspaces 
  left 
  by 
  the 
  op- 
  

   position 
  of 
  the 
  oval 
  cell-mouths 
  are 
  entirely 
  filled 
  by 
  very 
  minute 
  

   interstitial 
  tubuli," 
  there 
  cannot 
  be 
  any 
  possibility, 
  even 
  in 
  fragments, 
  

   of 
  confounding 
  one 
  with 
  the 
  other. 
  

  

  21. 
  Ptilodictya, 
  sp. 
  

  

  I 
  have 
  a 
  few 
  fragments 
  of 
  another 
  well-marked 
  species, 
  but 
  not 
  in 
  

   such 
  a 
  state 
  of 
  preservation 
  as 
  will 
  allow 
  of 
  detailed 
  description. 
  

   Still, 
  if 
  I 
  describe 
  it 
  to 
  the 
  best 
  of 
  my 
  ability, 
  it 
  may 
  be 
  that 
  other 
  

   workers 
  may 
  recognize 
  the 
  type 
  and 
  in 
  their 
  researches 
  obtain 
  better 
  

   specimens 
  than 
  I 
  can 
  boast 
  of. 
  

  

  Zoarium 
  a 
  thin 
  flattened 
  frond 
  of 
  unknown 
  dimensions. 
  Zooecia 
  

   arranged 
  in 
  two 
  series, 
  but 
  with 
  no 
  distinct 
  median 
  row 
  or 
  rows. 
  

   The 
  two 
  series 
  seem 
  to 
  rise 
  from 
  a 
  common 
  point, 
  then 
  bending, 
  one 
  

   series 
  to 
  the 
  right, 
  and 
  the 
  other 
  to 
  the 
  left, 
  with 
  a 
  slight 
  curve. 
  

   Orifices 
  of 
  the 
  cells 
  very 
  minute 
  ; 
  ten 
  of 
  them 
  occupy 
  a 
  line. 
  

  

  Locality. 
  Tickwood 
  beds, 
  Wo. 
  25. 
  

  

  If 
  this 
  species 
  has 
  not 
  been 
  previously 
  described, 
  I 
  would 
  suggest 
  

   for 
  it 
  the 
  name 
  of 
  Ptilodictya 
  minuta. 
  

  

  Other 
  very 
  doubtful 
  species 
  of 
  Silurian 
  Polyzoa 
  which 
  I 
  have 
  

   found 
  in 
  these 
  Shales 
  1 
  shall 
  have 
  to 
  rework. 
  At 
  the 
  present 
  time 
  

   I 
  cannot 
  do 
  more 
  than 
  say 
  that 
  there 
  are 
  still 
  a 
  few 
  undescribed 
  

   forms 
  left. 
  

  

  I 
  have 
  endeavoured, 
  in 
  the 
  above 
  paper, 
  to 
  give 
  as 
  few 
  microsco- 
  

   pical 
  details 
  as 
  possible, 
  because 
  these 
  seemed 
  to 
  me 
  to 
  be 
  rather 
  out 
  

   of 
  place. 
  I 
  cannot, 
  however, 
  let 
  the 
  paper 
  pass 
  beyond 
  my 
  control 
  

   without 
  saying 
  that 
  every 
  species 
  recorded 
  has 
  been 
  examined 
  macro- 
  

   scopically 
  and 
  microscopically. 
  The 
  sections 
  prepared 
  have 
  revealed 
  

   many 
  unexpected 
  features 
  that 
  will 
  help 
  to 
  throw 
  some 
  light 
  at 
  

   least 
  upon 
  the 
  development 
  of 
  the 
  Polyzoa 
  generally, 
  and 
  upon 
  the 
  

   biological 
  history 
  of 
  the 
  Silurian 
  Polyzoa 
  in 
  particular. 
  

  

  