﻿200 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  arrangement 
  throughout 
  the 
  whole 
  thallus 
  such 
  as 
  this 
  form 
  

   possesses 
  is, 
  however, 
  not 
  observed 
  among 
  the 
  coralhne 
  algae 
  

   which 
  for 
  the 
  most 
  part 
  possess 
  only 
  a 
  flat, 
  incrusting 
  thallus 
  and 
  

   in 
  the 
  erect 
  forms, 
  as 
  in 
  Corallina, 
  are 
  bifurcating 
  or 
  irregularly 
  

   branching, 
  mostly 
  in 
  but 
  one 
  plane. 
  The 
  habitus 
  of 
  Primicorallina 
  

   as 
  restored 
  in 
  this 
  publication 
  [see 
  pi. 
  i, 
  fig. 
  2], 
  is 
  distinctly 
  that 
  

   of 
  one 
  of 
  the 
  verticillate 
  Siphoneae 
  and 
  well 
  comparable 
  to 
  that 
  of 
  

   Dasycladus 
  or 
  Polyphysa 
  and 
  other 
  genera 
  of 
  the 
  Dasycladaceae. 
  

   Since 
  calcification 
  takes 
  place 
  also 
  in 
  several 
  of 
  the 
  genera 
  of 
  this 
  

   order 
  of 
  algae, 
  and 
  other 
  calcareous 
  verticillate 
  Siphoneae 
  were 
  

   already 
  abundant 
  in 
  the 
  Lower 
  Siluric 
  seas, 
  as 
  shown 
  by 
  Stolley, 
  

   it 
  is 
  preferable 
  to 
  place 
  Primicorallina 
  with 
  the 
  verticillate 
  

   Siphoneae. 
  

  

  A 
  reference 
  of 
  Primicorallina 
  to 
  the 
  Dasycladaceae 
  invites 
  com- 
  

   parison 
  to 
  the 
  other 
  verticillate 
  Siphoneae 
  described 
  by 
  Stolley 
  

   from 
  the 
  Swedish 
  Lower 
  Siluric. 
  The 
  latter 
  forms 
  differ 
  in 
  having 
  

   the 
  branchlets 
  incrusted 
  like 
  the 
  recent 
  calcareous 
  genera 
  of 
  Dasy- 
  

   cladaceae 
  (Cymopolia, 
  Borneteila 
  and 
  Neomeris), 
  to 
  such 
  an 
  ex- 
  

   tent 
  that 
  a 
  solid 
  cylindric 
  mantle 
  is 
  form-ed 
  in 
  which 
  the 
  branch- 
  

   lets 
  are 
  imbedded. 
  In 
  Primicorallina 
  the 
  incrustation 
  of 
  the 
  axial 
  

   cell 
  and 
  of 
  the 
  branchlets 
  is 
  comparatively 
  slight, 
  so 
  that 
  all 
  the 
  

   branchlets 
  remain 
  free. 
  This 
  is 
  obviously 
  only 
  a 
  difference 
  in 
  grade 
  

   of 
  calcification. 
  Another 
  difference 
  rests 
  seemingly 
  in 
  the 
  segmen- 
  

   tation 
  of 
  the 
  stem 
  which 
  suggests 
  a 
  composition 
  of 
  the 
  stem 
  of 
  

   more 
  than 
  one 
  cell 
  while 
  in 
  the 
  verticillate 
  Siphoneae 
  it 
  consists 
  of 
  

   but 
  one, 
  the 
  axial 
  cell. 
  But 
  it 
  is 
  here 
  to 
  be 
  remembered 
  that 
  on 
  

   one 
  hand 
  the 
  axial 
  canal 
  in 
  Primicorallina 
  shows 
  no 
  or 
  but 
  little 
  

   contraction 
  (as 
  far 
  as 
  can 
  be 
  seen 
  from 
  the 
  few 
  type 
  specimens 
  

   without 
  breaking 
  them) 
  at 
  the 
  articulations 
  and 
  may 
  well 
  result 
  

   from 
  a 
  single 
  axial 
  cell 
  and 
  that, 
  on 
  the 
  other 
  hand, 
  an 
  articulation 
  

   of 
  the 
  whole 
  thallus 
  without 
  subdivision 
  of 
  the 
  axial 
  cell 
  exists 
  

   also 
  in 
  the 
  recent 
  Cymopolia. 
  

  

  From 
  Arthroporella 
  Stolley, 
  which 
  consists 
  of 
  a 
  chain 
  of 
  spheric 
  

   and 
  pear-shaped 
  bodies 
  such 
  as 
  the 
  branchlets 
  of 
  Primicorallina 
  

   might 
  also 
  form 
  when 
  seen 
  in 
  sections, 
  the 
  latter 
  genus 
  differs 
  in 
  

   having 
  these 
  bodies 
  articulate 
  while 
  in 
  Arthroporella 
  the 
  incrusta- 
  

   tion 
  is 
  continuous 
  and 
  is 
  also 
  distinctly 
  porous. 
  

  

  It 
  is 
  very 
  probable 
  that 
  Primicorallina 
  has 
  not 
  only 
  interest 
  as 
  

   one 
  of 
  the 
  earliest 
  known 
  calcareous 
  verticillate 
  Siphoneae 
  but 
  that 
  

   it 
  is 
  also 
  of 
  importance 
  in 
  explaining 
  the 
  origin 
  of 
  certain 
  Trenton 
  

   lim»estones 
  of 
  granular 
  and 
  oolitic 
  texture. 
  Small 
  grains 
  which 
  

  

  