﻿346 
  G. 
  W. 
  SHRUESOLE 
  ON 
  THAMNISCUS. 
  

  

  Palaeozoic 
  Polyzoa, 
  when 
  seen 
  under 
  favourable 
  circumstances, 
  are 
  

   found 
  to 
  have 
  been 
  protected 
  by 
  spines 
  either 
  long 
  or 
  short. 
  In 
  

   this 
  respect 
  Thamniscus 
  crassus 
  is 
  no 
  exception 
  ; 
  for 
  notwithstanding 
  

   the 
  natural 
  and 
  often 
  artificial 
  weathering 
  to 
  which 
  the 
  Dudley 
  fossils 
  

   are 
  subject, 
  there 
  are 
  still 
  to 
  be 
  seen 
  little 
  irregularities 
  on 
  the 
  surface, 
  

   which 
  when 
  seen 
  in 
  profile 
  leave 
  no 
  doubt 
  as 
  to 
  their 
  being 
  the 
  re- 
  

   mains 
  of 
  spines 
  ; 
  this 
  is 
  confirmed 
  by 
  the 
  observations 
  of 
  Mr. 
  Vine, 
  

   who 
  has 
  noticed 
  the 
  base 
  of 
  spiniferous 
  processes 
  in 
  fragments 
  from 
  

   the 
  Wenlock 
  shale*. 
  

  

  As 
  yet 
  we 
  know 
  of 
  only 
  the 
  three 
  species 
  of 
  Thamniscus 
  which 
  I 
  

   have 
  referred 
  to 
  as 
  occurring 
  severally 
  in 
  the 
  Silurian, 
  Carboniferous, 
  

   and 
  Permian 
  periods. 
  We 
  have 
  least 
  knowledge 
  of 
  the 
  Carboniferous 
  

   species, 
  for 
  the 
  reason 
  that 
  as 
  yet 
  it 
  has 
  only 
  been 
  found 
  in 
  fragments. 
  

   The 
  Silurian 
  species 
  is 
  probably 
  the 
  more 
  compact 
  in 
  growth, 
  and 
  

   the 
  Carboniferous 
  and 
  Permian 
  the 
  more 
  vigorous 
  ; 
  the 
  last 
  is 
  more 
  

   outspread 
  in 
  its 
  bifurcation. 
  As 
  yet 
  I 
  know 
  of 
  no 
  older 
  form 
  than 
  

   the 
  Dudley 
  species. 
  

  

  I 
  have 
  to 
  acknowledge 
  my 
  indebtedness 
  to 
  Prof. 
  T. 
  M'.Kenny 
  

   Hughes, 
  for 
  giving 
  me 
  facilities 
  for 
  studying 
  the 
  Polyzoa 
  of 
  the 
  

   AVoodwardian 
  Museum. 
  

  

  * 
  Quart, 
  Journ. 
  Geol. 
  Soc, 
  vol. 
  xxxviii. 
  p. 
  60. 
  

  

  