﻿Derby 
  — 
  Stem 
  Structure 
  of 
  JPsaronius 
  Brasiliensis. 
  489 
  

  

  Art. 
  XLIII. 
  — 
  Observations 
  on 
  the 
  Stem 
  Structure 
  of 
  

   JPsaronius 
  Brasiliensis 
  ; 
  by 
  Orville 
  A. 
  Derby. 
  

  

  [Preliminary 
  note 
  in 
  advance 
  of 
  the 
  Annaes 
  do 
  Servigo 
  Geologico 
  e 
  Miner- 
  

   alogico 
  do 
  Brasil.] 
  

  

  It 
  having 
  been 
  recently 
  established 
  by 
  Count 
  Solms-Laubach* 
  

   that 
  the 
  slice 
  of 
  a 
  Psaronius 
  trunk 
  preserved 
  in 
  the 
  Paris 
  

   museum, 
  which 
  has 
  become 
  so 
  well 
  known 
  through 
  the 
  studies 
  

   of 
  Brongniart 
  and 
  Zeiller 
  under 
  the 
  name 
  of 
  Psaronius 
  

   brasiliensis 
  (possibly 
  not 
  identical 
  with 
  the 
  fossil 
  so 
  named 
  by 
  

   Unger), 
  is 
  a 
  part 
  of 
  a 
  specimen 
  taken, 
  in 
  1839, 
  from 
  the 
  

   National 
  Museum 
  of 
  Rio 
  de 
  Janeiro 
  to 
  Paris 
  to 
  be 
  cut, 
  and 
  

   that 
  other 
  slices 
  were 
  preserved 
  in 
  the 
  museums 
  of 
  Rio 
  de 
  

   Janeiro, 
  London 
  and 
  Strasbourg, 
  it 
  occurred 
  to 
  me 
  that, 
  hav- 
  

   ing 
  the 
  Rio 
  slice 
  at 
  hand, 
  there 
  was 
  a 
  possibility 
  of 
  determin- 
  

   ing 
  through 
  the 
  aid 
  of 
  photographs 
  and 
  dimensional 
  notes 
  on 
  

   the 
  other 
  slices, 
  the 
  relative 
  position 
  and 
  mutual 
  relations 
  of 
  

   the 
  different 
  known 
  parts 
  of 
  the 
  original 
  trunk. 
  Through 
  

   the 
  extreme 
  courtesy 
  of 
  Drs. 
  J. 
  B. 
  Lacerda 
  and 
  A. 
  Smith 
  

   Woodward 
  of 
  the 
  Rio 
  de 
  Janeiro 
  and 
  London 
  museums, 
  of 
  

   Prof. 
  R. 
  Zeiller 
  and 
  Count 
  Solms-Laubach 
  of 
  Paris 
  and 
  Stras- 
  

   bourg, 
  the 
  necessary 
  material 
  for 
  the 
  projected 
  study 
  was 
  

   readily 
  obtained. 
  

  

  The 
  alignment 
  of 
  the 
  various 
  slices, 
  represented 
  individually 
  

   in 
  fig. 
  l,f 
  was 
  found 
  to 
  be 
  an 
  easy 
  matter, 
  since 
  one 
  face 
  of 
  

   each 
  of 
  the 
  Paris 
  and 
  Strasbourg 
  ones, 
  having 
  been 
  only 
  par- 
  

   tially 
  evened 
  up 
  by 
  cutting, 
  retains 
  a 
  part 
  of 
  the 
  original 
  frac- 
  

   tured 
  surface 
  and 
  thus 
  shows 
  that 
  these 
  are 
  the 
  stub 
  ends 
  of 
  the 
  

   original 
  specimen. 
  Between 
  these 
  end 
  slices 
  the 
  Rio 
  and 
  

   London 
  ones 
  readily 
  fall 
  into 
  place 
  through 
  the 
  agreement 
  of 
  

   accidental 
  and 
  structural 
  features 
  on 
  the 
  opposing 
  sides 
  of 
  the 
  

   saw 
  cuts 
  by 
  which 
  they 
  had 
  been 
  separated. 
  The 
  Rio 
  slice, 
  

   not 
  having 
  been 
  evened 
  up, 
  shows 
  that 
  in 
  the 
  first 
  cutting 
  

   nearly 
  5 
  mm 
  of 
  material 
  must 
  have 
  been 
  lost 
  and 
  in 
  the 
  restora- 
  

   tions 
  in 
  figs. 
  2 
  and 
  3 
  this 
  width 
  has 
  been 
  assigned 
  to 
  the 
  

   various 
  saw 
  cuts, 
  though 
  it 
  is 
  probably 
  too 
  great 
  for 
  those 
  sub- 
  

   sequently 
  made. 
  According 
  to 
  information 
  received 
  from 
  

   Prof. 
  Zeiller 
  a 
  thin 
  slice 
  (5 
  mm 
  ±), 
  now 
  in 
  the 
  Paris 
  museum, 
  

   was 
  cut 
  from 
  the 
  lower 
  end 
  of 
  the 
  original 
  Paris 
  specimen 
  to 
  

   even 
  it 
  up, 
  and 
  apparently 
  a 
  similar 
  operation 
  had 
  been 
  per- 
  

   formed 
  on 
  the 
  upper 
  end 
  of 
  the 
  first 
  London 
  one, 
  since 
  its 
  

  

  * 
  Uber 
  die 
  Schicksale 
  der 
  als 
  Psaronius 
  brasiliensis 
  beschriebenen 
  Fossil- 
  

   reste 
  unserer 
  Museen, 
  Festschrift 
  zur 
  Feier 
  des 
  70 
  Geburtstages 
  von 
  P. 
  

   Ascherson, 
  1904. 
  

  

  f 
  These 
  sections, 
  as 
  also 
  those 
  of 
  figs. 
  2 
  and 
  3, 
  are 
  about 
  two-fifths 
  natural 
  

  

  