﻿PLATE 
  VII. 
  

  

  LlCHENALIA 
  CONCENTRICA 
  VdV. 
  PARVULA 
  Hall. 
  

  

  Page 
  117. 
  

   Fig. 
  1. 
  A 
  fragment 
  of 
  this 
  form 
  of 
  Lichenalia 
  which 
  has 
  grown 
  upon 
  the 
  upper 
  

  

  surface 
  of 
  a 
  Strophostylus. 
  

   Fig. 
  2 
  An 
  enlargement 
  of 
  a 
  portion 
  of 
  the 
  above, 
  showing 
  the 
  cells 
  to 
  be 
  much 
  

   smaller 
  and 
  more 
  distinctly 
  circular 
  than 
  in 
  the 
  ordinary 
  form 
  of 
  

   L. 
  concentrica. 
  

  

  Lichenalia 
  concentrica 
  Hall. 
  

  

  Page 
  116. 
  

  

  Fig. 
  3. 
  An 
  enlargement 
  of 
  a 
  young 
  Lichenalia, 
  showing 
  it 
  as 
  it 
  has 
  grown 
  attached 
  

   to 
  the 
  surface 
  of 
  an 
  Atrypa. 
  

  

  Figs. 
  4, 
  5, 
  7, 
  8. 
  Enlargements 
  from 
  the 
  surfaces 
  of 
  Lichenalise 
  as 
  presented 
  in 
  

   different 
  individuals. 
  Figures 
  4 
  and 
  5 
  are 
  respectively 
  three 
  and 
  

   four 
  diameters 
  of 
  the 
  young 
  specimens 
  attached 
  to 
  Fenestella. 
  (See 
  

   pi. 
  12, 
  fig. 
  3.) 
  

  

  Fig. 
  6. 
  An 
  enlargement 
  to 
  about 
  four 
  diameters 
  of 
  a 
  group 
  of 
  two 
  young 
  Lich- 
  

   enalise 
  and 
  a 
  young 
  Favosites, 
  attached 
  to 
  the 
  shell 
  of 
  Stropho- 
  

   stylus. 
  

  

  Figs. 
  9, 
  10, 
  Enlargements 
  from 
  the 
  lower 
  surfaces 
  of 
  different 
  individuals, 
  show- 
  

   ing 
  the 
  variable 
  conditions 
  of 
  the 
  epitheca. 
  In 
  fig. 
  9 
  the 
  cell-par- 
  

   titions 
  are 
  shown 
  through 
  the 
  texture 
  ; 
  and 
  fig. 
  10 
  presents 
  a 
  fibrous 
  

   condition, 
  from 
  the 
  removal 
  of 
  the 
  epithecal 
  covering 
  leaving 
  the 
  

   projecting 
  cell-walls. 
  

  

  Fig. 
  11. 
  An 
  enlarged 
  transverse 
  section 
  of 
  a 
  specimen 
  similar 
  to 
  fig. 
  4 
  of 
  plate 
  

   6, 
  showing 
  the 
  depth 
  of 
  the 
  cells 
  and 
  the 
  thickness 
  of 
  the 
  epitheca 
  

   in 
  old 
  individuals. 
  

  

  The 
  variations 
  in 
  expression, 
  in 
  the 
  many 
  forms 
  of 
  this 
  species, 
  

   the 
  size, 
  proportion 
  and 
  arrangement 
  of 
  the 
  cellules 
  upon 
  the 
  sur- 
  

   face, 
  and 
  the 
  aspects 
  produced 
  by 
  weathering 
  or 
  maceration 
  are 
  so 
  

   great 
  as 
  often 
  to 
  induce 
  a 
  reference 
  to 
  distinct 
  species. 
  It 
  does 
  

   not, 
  however, 
  seem 
  possible 
  to 
  convey 
  in 
  a 
  satisfactory 
  manner, 
  

   the 
  characters 
  as 
  they 
  appear 
  to 
  the 
  eye 
  and 
  under 
  a 
  lens. 
  

  

  Sageistella 
  elegans 
  Hall. 
  

  

  Page 
  118. 
  

  

  Fig. 
  12. 
  The 
  right 
  valve 
  of 
  Arribonychia 
  acutirostra, 
  showing 
  the 
  encrusting 
  

  

  membraneous 
  bryozoan 
  upon 
  its 
  surface 
  . 
  

   Fig. 
  13. 
  An 
  enlargement 
  of 
  a 
  portion 
  of 
  the 
  same 
  specimen 
  to 
  show 
  the 
  tubular 
  

  

  cells 
  and 
  their 
  apertures. 
  

  

  