﻿Report 
  of 
  the 
  State 
  Geologist. 
  893 
  

  

  It 
  will 
  certainly 
  be 
  of 
  advantage 
  to 
  the 
  student 
  in 
  the 
  identifica- 
  

   tion 
  of 
  species. 
  The 
  names 
  of 
  course 
  refer 
  to 
  the 
  character 
  of 
  

   the 
  carinas 
  : 
  

  

  Group 
  a. 
  Fenestella 
  (humilis), 
  with 
  low 
  smooth 
  carinas. 
  

   Group 
  /?. 
  Fenestella 
  (nodata), 
  with 
  nodes 
  or 
  low 
  nodose 
  

  

  carinas. 
  

   Group 
  y. 
  Fenestella 
  (laminata), 
  with 
  very 
  prominent, 
  equal, 
  

  

  thin 
  carinas. 
  

   Group 
  d. 
  Fenestella 
  (mediadilata), 
  with 
  carinas 
  expanding 
  

  

  midway 
  then 
  contracting, 
  the 
  expanded 
  portion 
  

  

  having 
  nodes 
  on 
  their 
  margin. 
  

   Group 
  e. 
  Fenestella 
  (summidilata), 
  with 
  prominent 
  carinas 
  

  

  summits 
  expanded, 
  margins 
  smooth. 
  

   Group 
  #. 
  Fenestella 
  (prastexta), 
  with 
  prominent 
  carinas 
  

  

  expanded 
  at 
  the 
  summit, 
  margins 
  nodose. 
  

  

  POLYPOKA, 
  McCoy. 
  

  

  The 
  genus 
  Polypora 
  was 
  founded 
  by 
  McCoy, 
  1845 
  (Carb. 
  Foss. 
  

   of 
  Ireland, 
  p. 
  206); 
  ety. 
  noXus 
  many 
  and 
  rtopo? 
  pore, 
  having 
  a 
  

   zoarium 
  like 
  that 
  of 
  Fenestella, 
  but 
  no 
  median 
  ridge 
  or 
  carinas 
  

   on 
  the 
  celluliferous 
  face 
  of 
  the 
  branches, 
  and 
  with 
  three 
  or 
  more 
  

   ranges 
  of 
  cell 
  apertures. 
  

  

  The 
  typical 
  forms 
  of 
  Fenestella 
  and 
  Polypora 
  are 
  character- 
  

   istic 
  and 
  very 
  easily 
  distinguished, 
  but 
  there 
  are 
  many 
  forms 
  

   which 
  combine 
  the 
  characters 
  of 
  both 
  genera, 
  having 
  on 
  some 
  

   branches, 
  or 
  on 
  portions 
  of 
  them, 
  two 
  ranges 
  of 
  cell 
  apertures, 
  

   while 
  on 
  other 
  branches, 
  or 
  on 
  the 
  wider 
  portions 
  of 
  the 
  same 
  

   branch, 
  three 
  or 
  more 
  ranges 
  of 
  apertures 
  occur, 
  for 
  example, 
  

   in 
  F. 
  jpaxillati 
  and 
  F. 
  Fudora 
  of 
  the 
  Lower 
  Helderberg 
  group. 
  

   As 
  the 
  genera 
  are 
  now 
  constituted, 
  it 
  is 
  simply 
  a 
  question 
  of 
  

   individual 
  opinion 
  as 
  to 
  which 
  genus 
  these 
  forms 
  belong 
  ; 
  their 
  

   characters 
  agreeing 
  equally 
  well 
  with 
  either. 
  Others 
  have 
  met 
  

   with 
  the 
  same 
  difficulty 
  in 
  classifying 
  species. 
  

  

  Prof. 
  Claypole, 
  Geol. 
  Mag., 
  says 
  : 
  " 
  As 
  Palasontology 
  advances 
  

   we 
  continually 
  find 
  new 
  forms 
  filling 
  the 
  gaps 
  between 
  others 
  

   already 
  known, 
  and 
  such 
  connecting 
  links 
  may 
  with 
  justice 
  be 
  

   referred 
  to 
  either 
  of 
  the 
  two 
  genera 
  which 
  they 
  connect. 
  Such 
  

  

  