﻿The 
  Fauna 
  of 
  the 
  Niagara 
  Group. 
  117 
  

  

  rior 
  surface 
  is 
  worn, 
  it 
  presents 
  a 
  grooved 
  and 
  striate 
  ap- 
  

   pearance, 
  indicating 
  the 
  mode 
  of 
  growth 
  in 
  the 
  cells 
  and 
  cell- 
  

   walls, 
  which 
  are 
  usually 
  procumbent 
  at 
  the 
  commencement 
  of 
  

   their 
  growth, 
  and 
  then 
  turn 
  upward. 
  The 
  celluliferous 
  

   face 
  presents 
  numerous 
  cell 
  openings 
  which 
  may 
  be 
  closely 
  or 
  

   more 
  distantly 
  arranged, 
  and 
  which 
  vary 
  from 
  circular 
  to 
  oval, 
  

   and 
  even 
  subquadrangular 
  in 
  form, 
  depending 
  upon 
  their 
  

   mode 
  of 
  growth 
  and 
  in 
  part 
  upon 
  the 
  condition 
  of 
  preserva- 
  

   tion. 
  These 
  bodies 
  do 
  not 
  always 
  preserve 
  the 
  expanded 
  form 
  

   indicated, 
  but 
  the 
  margins 
  become 
  contracted 
  and 
  infolded, 
  so 
  

   that 
  the 
  non 
  celluliferous 
  faces 
  come 
  into 
  near 
  contact, 
  and 
  

   assume 
  an 
  apparently 
  solid 
  form, 
  with 
  cell-apertures 
  covering 
  

   the 
  entire 
  surface. 
  In 
  their 
  young 
  state 
  they 
  are 
  frequently 
  

   found 
  attached 
  to 
  other 
  fossils, 
  and 
  this 
  is 
  probably 
  the 
  con- 
  

   dition 
  of 
  all 
  in 
  their 
  earlier 
  stages 
  of 
  growth 
  ; 
  the 
  mode 
  of 
  

   growth 
  and 
  ultimate 
  form 
  being 
  greatly 
  dependent 
  upon 
  the 
  

   nature 
  of 
  the 
  body 
  to 
  which 
  the 
  germ 
  has 
  originally 
  been 
  

   affixed. 
  In 
  the 
  expanded 
  forms 
  the 
  cell-tubes 
  are 
  short, 
  and 
  

   the 
  increase 
  is 
  by 
  lateral 
  extension 
  of 
  new 
  cells, 
  until 
  the 
  

   fronds 
  sometimes 
  reach 
  a 
  diameter 
  of 
  thirty 
  centimetres. 
  

   When 
  the 
  frond 
  becomes 
  corrugated 
  or 
  infolded 
  in 
  its 
  young 
  

   state, 
  and 
  assumes 
  a 
  compact 
  form, 
  the 
  cell-tubes 
  become 
  elon- 
  

   gated 
  as 
  shown 
  in 
  fig. 
  11 
  of 
  plate 
  5, 
  but 
  I 
  am 
  unable 
  to 
  find 
  

   that 
  any 
  of 
  them 
  assume 
  characters 
  incompatible 
  with 
  the 
  

   genus 
  in 
  its 
  typical 
  forms. 
  After 
  examining 
  a 
  large 
  number 
  

   of 
  specimens, 
  I 
  am 
  unable 
  to 
  distinguish 
  any 
  characters 
  mark- 
  

   ing 
  a 
  specific 
  difference 
  between 
  the 
  expanded 
  forms, 
  like 
  figs. 
  

   4, 
  9 
  and 
  10, 
  of 
  plate 
  6, 
  and 
  those 
  which 
  assume 
  an 
  irregular 
  

   and 
  more 
  solid 
  aspect, 
  as 
  in 
  figs. 
  9, 
  11 
  and 
  12, 
  of 
  plate 
  5. 
  

  

  LlCHENALIA 
  CONCENTRICA 
  Var. 
  PARVULA. 
  

  

  Plate 
  7, 
  Figs. 
  1, 
  2. 
  

  

  Lichenalia 
  conceutrica 
  var. 
  parvula 
  HaJjL.. 
  Doc. 
  Edit. 
  28th 
  Rep. 
  St. 
  Mus. 
  Nat. 
  

   Hist. 
  Explanation 
  of 
  pi. 
  7, 
  figs. 
  1, 
  2. 
  1876. 
  

  

  This 
  form, 
  indicated 
  as 
  a 
  variety 
  of 
  L. 
  concentrica, 
  is 
  distin- 
  

   guished 
  by 
  its 
  smaller 
  cell-apertures, 
  as 
  shown 
  in 
  fig. 
  2, 
  which 
  

   is 
  enlarged 
  to 
  the 
  same 
  degree 
  as 
  fig. 
  7. 
  In 
  its 
  mode 
  of 
  growth 
  

   and 
  other 
  characters 
  it 
  does 
  not 
  differ 
  from 
  the 
  ordinary 
  forms 
  

   of 
  Lichenalia. 
  

  

  Lichenalia 
  concentrica 
  var. 
  maculata 
  n. 
  var. 
  

  

  Plate 
  6, 
  Figs. 
  3, 
  5 
  and 
  6. 
  

  

  Celluliferous 
  face, 
  flat, 
  concave 
  or 
  convex; 
  cell-apertures 
  

   round, 
  or 
  broadly 
  oval, 
  and 
  when 
  entire, 
  preserving 
  a 
  project- 
  

  

  