﻿106 
  PRINCIPAL 
  DAWSON 
  ON 
  PROTOTAXITES 
  AND 
  

  

  I 
  have 
  sent 
  a 
  fragment 
  of 
  the 
  Campbellton 
  Prototaccites 
  to 
  Mr. 
  

   Carruthers, 
  and 
  have 
  no 
  donbt 
  that, 
  if 
  sliced, 
  it 
  will 
  show 
  the 
  

   peculiar 
  state 
  of 
  mineralization 
  above 
  described. 
  

  

  Mr. 
  Hicks 
  having 
  been 
  so 
  kind 
  as 
  to 
  send 
  me 
  a 
  specimen 
  of 
  the 
  

   Pachytheca 
  from 
  Corwen, 
  I 
  have 
  compared 
  it 
  with 
  Mr. 
  Etheridge's 
  

   figures 
  and 
  description, 
  and 
  with 
  similar 
  objects 
  from 
  this 
  country 
  

   and 
  elsewhere. 
  Mr. 
  Etheridge's 
  figures 
  very 
  accurately 
  represent 
  

   the 
  specimen 
  examined 
  by 
  me; 
  but 
  I 
  would 
  make 
  the 
  following 
  

   additional 
  remarks. 
  The 
  specimen 
  is 
  globular, 
  but 
  slightly 
  flattened 
  

   in 
  the 
  plane 
  of 
  the 
  bed. 
  It 
  is 
  three 
  millimetres 
  in 
  diameter, 
  and 
  

   consists 
  of 
  an 
  internal 
  globular 
  nucleus 
  of 
  granular 
  texture, 
  rather 
  

   more 
  than 
  one 
  millimetre 
  in 
  diameter, 
  surrounded 
  by 
  a 
  thick 
  testa 
  

   or 
  outer 
  envelope 
  of 
  radiating 
  fibres. 
  The 
  fibrous 
  part 
  is 
  in 
  the 
  same 
  

   state 
  of 
  preservation 
  as 
  one 
  of 
  the 
  kinds 
  of 
  associated 
  fossil 
  wood, 
  

   the 
  walls 
  of 
  the 
  fibres 
  being 
  carbonized 
  and 
  the 
  cavities 
  filled 
  with 
  

   transparent 
  silica. 
  Under 
  high 
  powers 
  the 
  " 
  spore-like 
  bodies 
  " 
  

   referred 
  to 
  by 
  Mr. 
  Etheridge 
  resolve 
  themselves 
  into 
  alternate 
  swel- 
  

   lings 
  and 
  contractions 
  of 
  the 
  cavities 
  of 
  certain 
  of 
  the 
  fibres, 
  others 
  

   presenting 
  a 
  more 
  uniform 
  cylindrical 
  form. 
  The 
  latter 
  occasionally 
  

   show 
  the 
  irregular 
  transverse 
  bands 
  observed 
  in 
  the 
  wood 
  of 
  Protc- 
  

   taocites 
  from 
  the 
  same 
  locality. 
  The 
  internal 
  nucleus 
  is 
  apparently 
  

   wholly 
  granular, 
  as 
  if 
  it 
  had 
  been 
  composed 
  of 
  parenchymatous 
  

   tissue. 
  

  

  There 
  are 
  in 
  my 
  cabinet 
  specimens 
  of 
  similar 
  bodies 
  in 
  a 
  pyritized 
  

   state, 
  from 
  the 
  Upper 
  Silurian 
  (Lower 
  Helderberg) 
  of 
  Cape 
  Bon 
  Ami, 
  

   in 
  New 
  Brunswick, 
  where 
  they 
  are 
  found 
  associated 
  with 
  fragments 
  

   of 
  wood 
  of 
  Prototaccites. 
  Though 
  on 
  the 
  whole 
  less 
  perfectly 
  pre- 
  

   served, 
  as 
  to 
  structure, 
  than 
  the 
  "Welsh 
  specimens, 
  when 
  sliced 
  in 
  

   certain 
  directions 
  they 
  present 
  traces 
  of 
  a 
  micropyle 
  and 
  embryo, 
  

   and 
  are, 
  in 
  my 
  judgment, 
  true 
  seeds. 
  

  

  There 
  seems 
  little 
  doubt 
  that 
  these 
  New 
  Brunswick 
  specimens 
  and 
  

   those 
  from 
  Corwen 
  may 
  be 
  referred 
  to 
  Brongniart's 
  genus 
  JEtheo- 
  

   testa, 
  and 
  that 
  they 
  are 
  nearly 
  allied 
  to 
  my 
  JEtheotesta 
  devonica 
  from 
  

   the 
  Devonian 
  of 
  Scotland 
  (discovered 
  by 
  Rev. 
  Thomas 
  Brown, 
  of 
  

   Edinburgh). 
  In 
  connexion 
  with 
  the 
  structures 
  observed 
  in 
  the 
  

   Corwen 
  specimens, 
  it 
  is 
  worthy 
  of 
  note 
  that 
  Brongniart 
  says 
  of 
  his 
  

   species 
  JE. 
  subglobosa, 
  from 
  the 
  coal-formation, 
  that 
  the 
  testa 
  is 
  

   " 
  thick, 
  homogeneous, 
  formed 
  of 
  fibres 
  or 
  elongated 
  cells 
  perpendi- 
  

   cular 
  to 
  the 
  surface. 
  These 
  fibres 
  appear, 
  in 
  one 
  specimen, 
  to 
  be 
  in- 
  

   termixed 
  with 
  Utile 
  globular 
  cells, 
  possibly 
  in 
  consequence 
  of 
  altera- 
  

   tion 
  of 
  the 
  tissue 
  "*. 
  This 
  is 
  precisely 
  the 
  appearance 
  presented 
  by 
  

   the 
  testa 
  of 
  Pachyiheca. 
  Brongniart's 
  JEtheotesta 
  is 
  undoubtedly 
  a 
  

   seed, 
  and 
  he 
  compares 
  it 
  with 
  the 
  nut-like 
  seeds 
  of 
  Taxineae* 
  

  

  Pachytheca 
  has 
  now 
  been 
  found 
  associated 
  with 
  Prototaccites, 
  not 
  

   only 
  at 
  Corwen, 
  but 
  also 
  in 
  the 
  Upper 
  Ludlow 
  of 
  England, 
  in 
  the 
  

   Upper 
  Silurian 
  of 
  Cape 
  Bon 
  Ami, 
  and 
  in 
  the 
  Lower 
  Devonian 
  of 
  

   Bordeaux 
  Quarry 
  opposite 
  Campbellton 
  in 
  New 
  Brunswick 
  ; 
  and 
  since 
  

   the 
  structure 
  of 
  the 
  Corwen 
  specimen 
  corresponds 
  with 
  that 
  of 
  Pro- 
  

  

  * 
  Annales 
  des 
  Sciences, 
  tome 
  xx. 
  serie 
  5. 
  

  

  