﻿Report 
  of 
  the 
  State 
  Geologist, 
  

  

  907 
  

  

  characteristic 
  features 
  of 
  this 
  species 
  are 
  represented 
  in 
  figures 
  

   53-55. 
  Figure 
  58 
  is 
  from 
  the 
  carina 
  of 
  an 
  undescribed 
  

   species. 
  

  

  The 
  species 
  in 
  which 
  the 
  carinse 
  vary 
  m 
  the 
  same 
  manner 
  as 
  

   the 
  groups 
  of 
  Fenestella 
  discussed 
  in 
  a 
  former 
  portion 
  of 
  this 
  

  

  56 
  

  

  58 
  

  

  57 
  

  

  paper, 
  may, 
  in 
  similar 
  manner, 
  be 
  designated 
  by 
  letters 
  of 
  the 
  

   Greek 
  alphabet. 
  

  

  Group 
  a 
  ; 
  with 
  a 
  thin, 
  slightly 
  elevated 
  carina 
  (fig. 
  52.) 
  

  

  Group 
  p 
  ; 
  with 
  low 
  nodose 
  carina. 
  

  

  Group 
  y 
  ; 
  with 
  the 
  prominent 
  carina, 
  equal 
  thickness 
  through- 
  

   out 
  (fig. 
  56.) 
  

  

  Group 
  8 
  ; 
  with 
  carina 
  expanded 
  midway 
  of 
  the 
  summit, 
  then 
  

   contracting, 
  the 
  expanded 
  portion 
  having 
  nodes 
  

   on 
  the 
  margin 
  (figs. 
  53-55.) 
  

  

  Group 
  e 
  ; 
  with 
  prominent 
  carina 
  with 
  smooth 
  expanded 
  summit 
  

   (fig. 
  57.) 
  

  

  These 
  groups 
  differ 
  from 
  the 
  corresponding 
  groups 
  of 
  Fenestella 
  

   in 
  the 
  strong 
  semi-circular 
  projections. 
  

  

  I 
  think 
  there 
  can 
  be 
  no 
  valid 
  objection 
  to 
  forming 
  a 
  new 
  genus 
  

   for 
  these 
  forms, 
  for 
  the 
  semi- 
  circular 
  projections, 
  frequently 
  

   uniting 
  and 
  connecting 
  adjacent 
  carinse, 
  are 
  certainly 
  of 
  as 
  much 
  

   generic 
  importance 
  as 
  the 
  connecting 
  plates 
  of 
  Unitrypa 
  or 
  the 
  

   connecting 
  bars 
  of 
  Isotrypa. 
  

  

  