﻿Report 
  of 
  the 
  State 
  Geologist. 
  

  

  885 
  

  

  apparent, 
  for 
  a 
  section 
  shows 
  that 
  the 
  cells 
  occupy 
  the 
  greater 
  

   portion 
  of 
  the 
  interior 
  of 
  the 
  dissepiment. 
  In 
  some 
  genera 
  inter- 
  

   mediate 
  cells 
  are 
  formed 
  which 
  have 
  their 
  apertures 
  on 
  the 
  

   dissepiments; 
  the 
  dissepiments 
  thus 
  presenting 
  the 
  same 
  appear- 
  

   ance 
  as 
  the 
  celluliferous 
  face 
  of 
  the 
  branches. 
  Though 
  in 
  one 
  

   case 
  the 
  dissepiment 
  is 
  apparently 
  solid 
  and 
  in 
  the 
  other 
  cellular, 
  

   a 
  transverse 
  section, 
  in 
  a 
  majority 
  of 
  cases, 
  shows 
  that 
  both 
  are 
  

   cellular, 
  varying 
  only 
  in 
  the 
  number 
  of 
  cells 
  occupying 
  the 
  

   dissepiment. 
  When 
  the 
  dissepiment 
  is 
  composed 
  of 
  two 
  cells, 
  

   one 
  from 
  the 
  side 
  of 
  each 
  adjacent 
  branch, 
  the 
  walls 
  separating 
  

   the 
  cells 
  may 
  be 
  of 
  variable 
  thickness, 
  though 
  frequently 
  not 
  

   thicker 
  than 
  the 
  walls 
  separating 
  the 
  cells 
  of 
  the 
  branches. 
  

   When 
  the 
  dissepiments 
  are 
  very 
  slender 
  and 
  long 
  the 
  deposit 
  

   separating 
  the 
  cells 
  may 
  be 
  of 
  considerable 
  thickness. 
  This 
  

   feature 
  will 
  be 
  illustrated 
  by 
  the 
  following 
  figures 
  : 
  

  

  Fig. 
  1 
  is 
  an 
  illustration 
  of 
  a 
  Fenestelloid 
  form 
  from 
  the 
  Ham- 
  

   ilton 
  group; 
  the 
  exterior 
  showing 
  two 
  ranges 
  of 
  cell 
  apertures 
  

   separated 
  by 
  a 
  median 
  keel 
  or 
  carina. 
  The 
  branches 
  are 
  united 
  

   by 
  apparently 
  solid 
  dissepiments, 
  but 
  a 
  section 
  of 
  the 
  interior 
  

   shows 
  the 
  dissepiments 
  to 
  be 
  composed 
  of 
  cells 
  in 
  precisely 
  the 
  

   same 
  manner 
  as 
  the 
  branches. 
  

  

  Fig. 
  2 
  represents 
  0. 
  paxillata 
  of 
  the 
  Lower 
  Helderberg 
  group, 
  

   showing 
  the 
  lateral 
  extension 
  of 
  the 
  cells 
  to 
  form 
  the 
  dissepiments. 
  

  

  Fig. 
  3 
  represents 
  Polypora 
  shumardi 
  of 
  the 
  Corniferous 
  

   limestone 
  and 
  shows 
  on 
  the 
  same 
  frond 
  both 
  apparently 
  solid 
  and 
  

   celluliferous 
  dissepiments, 
  some 
  of 
  the 
  dissepiments 
  having 
  the 
  

   characteristic 
  features 
  of 
  Phyllopora 
  and 
  others 
  those 
  of 
  Polypora 
  

  

  From 
  the 
  manner 
  of 
  the 
  formation 
  of 
  the 
  dissepiments 
  it 
  fol 
  

   lows 
  that 
  the 
  anastomosis 
  of 
  branches 
  and 
  connection 
  by 
  dissepi- 
  

  

  