﻿64 
  g. 
  r. 
  vine 
  on 
  the 
  wenlock 
  poltzoa. 
  

  

  17. 
  Ptilodictya 
  lanceolata. 
  

  

  Syn. 
  & 
  ref. 
  Flustra 
  lanceolata, 
  Goldf. 
  

  

  Ptilodictya 
  lanceolata, 
  Lonsd. 
  Sil. 
  Sys. 
  pi. 
  15. 
  figs. 
  11-11 
  e. 
  

  

  Zoarium 
  long, 
  narrow, 
  flat, 
  slightly 
  curved 
  longitudinally, 
  and 
  

   thin, 
  gradually 
  diminishing 
  to 
  a 
  fine 
  edge 
  ; 
  middle 
  cells 
  narrow, 
  

   small, 
  in 
  about 
  ten 
  rows 
  ; 
  lateral 
  cells 
  larger 
  and 
  arranged 
  in 
  rows 
  

   slightly 
  arched 
  from 
  the 
  middle 
  to 
  the 
  edge 
  ; 
  the 
  cells 
  themselves 
  

   placed 
  obliquely 
  both 
  with 
  respect 
  to 
  the 
  middle 
  of 
  the 
  zoarium 
  and 
  

   the 
  arch*. 
  

  

  Locality 
  and 
  Formation. 
  Wenlock 
  Limestone, 
  Dudley. 
  

  

  This 
  type 
  species 
  of 
  the 
  genus 
  is 
  a 
  very 
  fine 
  one 
  ; 
  but 
  it 
  is 
  

   questionable 
  whether 
  all 
  the 
  small 
  fragments 
  are 
  referable 
  to 
  this 
  

   species. 
  Lonsdale 
  himself 
  had 
  his 
  doubts 
  ; 
  for 
  he 
  says 
  " 
  fragments 
  of 
  

   probably 
  young 
  specimens 
  are 
  occasionally 
  found 
  in 
  the 
  Wenlock 
  

   Limestone." 
  

  

  In 
  the 
  ' 
  Wenlock 
  Shales 
  ' 
  localities 
  will 
  be 
  given. 
  I 
  have 
  found 
  a 
  

   number 
  of 
  fragments 
  of 
  two 
  species 
  of 
  this 
  genus. 
  By 
  far 
  the 
  largest 
  

   numbers 
  of 
  these 
  fragments 
  I 
  am 
  unable 
  to 
  identify 
  with 
  the 
  de- 
  

   scription 
  or 
  figures 
  given 
  by 
  Lonsdale 
  ; 
  yet 
  I 
  have 
  not 
  the 
  least 
  doubt 
  

   that 
  these 
  are 
  the 
  Ptilodictya 
  lanceolata 
  of 
  authors, 
  and 
  also 
  of 
  the 
  

   Catalogue 
  of 
  Cambr. 
  and 
  Sil. 
  Foss. 
  in 
  the 
  School 
  of 
  Mines. 
  Prom 
  

   the 
  Upper 
  Llandovery 
  to 
  the 
  Wenlock 
  Shale, 
  Mr. 
  Newton 
  gives 
  

   three 
  references 
  — 
  two 
  to 
  Ptilodictya 
  lanceolata, 
  Lonsd., 
  and 
  one 
  to 
  

   P. 
  scalp 
  ellum, 
  Lonsd. 
  As 
  no 
  other 
  references 
  are 
  given, 
  I 
  think 
  I 
  

   may 
  fairly 
  conclude 
  that 
  these 
  specimens 
  of 
  the 
  Shales 
  would 
  

   ordinarily 
  be 
  referred 
  to 
  P. 
  lanceolata, 
  Lonsd. 
  There 
  is, 
  however, 
  a 
  

   considerable 
  difference 
  between 
  the 
  Wenlock 
  species 
  and 
  this. 
  Under 
  

   these 
  circumstances 
  it 
  will, 
  I 
  think, 
  be 
  better 
  to 
  rename 
  and 
  rede- 
  

   scribe 
  one 
  of 
  the 
  two 
  species 
  found 
  in 
  the 
  Shales. 
  

  

  18. 
  Ptilodictya 
  lonsdalei, 
  sp. 
  n. 
  (Figs. 
  11-13.) 
  

  

  P. 
  lanceolota 
  of 
  authors 
  : 
  " 
  young 
  specimens," 
  Lonsd. 
  

  

  Zoarium 
  thin, 
  when 
  full-grown 
  lance-like, 
  one 
  edge 
  of 
  which 
  is 
  

   slightly 
  convex 
  : 
  base 
  rooted 
  (?) 
  either 
  to 
  some 
  foreign 
  object 
  or 
  to 
  

   a 
  parent 
  zoarium 
  ; 
  margins 
  non-celluliferous, 
  but 
  not 
  solid, 
  composed 
  

   of 
  a 
  loosely 
  compacted 
  " 
  endocystal" 
  layer. 
  Zooecia 
  on 
  both 
  sides, 
  

   separated, 
  but 
  not 
  by 
  a 
  laminar 
  axis 
  ? 
  ; 
  the 
  rows 
  of 
  ceils 
  divided 
  by 
  

   bars 
  which 
  bifurcate 
  at 
  intervals. 
  Two 
  rows 
  of 
  cells, 
  rather 
  longer 
  

   than 
  wide, 
  occupy 
  the 
  central 
  area, 
  giving 
  off 
  on 
  each 
  side 
  from 
  two 
  

   to 
  seven 
  laterally 
  oblique 
  rows. 
  This 
  character 
  is 
  only 
  seen 
  in 
  

   sections 
  : 
  externally 
  all 
  the 
  rows 
  of 
  cells, 
  from 
  four 
  to 
  sixteen, 
  appear 
  

   to 
  be 
  longitudinally 
  placed. 
  Aperture 
  of 
  zooecia 
  ovate, 
  and 
  nearly 
  

   as 
  large 
  as 
  the 
  subtubular 
  cells. 
  About 
  six 
  zooecia 
  occupy 
  the 
  space 
  

   of 
  a 
  line 
  measured 
  longitudinally 
  ; 
  and 
  about 
  eight 
  rows, 
  including 
  

   the 
  bars, 
  occur 
  in 
  the 
  same 
  space 
  in 
  a 
  transverse 
  direction. 
  At 
  the 
  

   distal 
  corners 
  of 
  all 
  the 
  cells 
  there 
  are 
  small 
  openings, 
  ranging 
  in 
  

   character 
  from 
  circular 
  to 
  ovate, 
  especially 
  towards 
  the 
  margins 
  of 
  the 
  

   zoarium. 
  This 
  is 
  one 
  of 
  the 
  most 
  constant 
  characters 
  of 
  the 
  species. 
  

  

  * 
  Lonsdale, 
  ' 
  Silurian 
  System,' 
  descriptive 
  text 
  of 
  pi. 
  15, 
  slightly 
  altered. 
  

  

  