﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  

  

  173 
  

  

  rr- 
  

  

  

  tions; 
  zooecia 
  subtubular, 
  more 
  or 
  less 
  oblique, 
  radially 
  arranged 
  

   about 
  a 
  central 
  axis 
  and 
  opening 
  on 
  all 
  sides 
  of 
  the 
  segments. 
  

  

  Helopora 
  fragilis 
  Hall 
  (Fig. 
  74) 
  

   (1852. 
  Pal 
  N. 
  Y. 
  2:44, 
  pi. 
  18, 
  fig. 
  3a-f) 
  

  

  Distinguishing 
  characters. 
  Minute 
  

   cylindric 
  or 
  clavate 
  zoarium 
  swollen 
  

   at 
  one 
  end; 
  oval 
  or 
  subangular 
  pores, 
  

   having 
  a 
  spiral 
  direction 
  around 
  the 
  

   stipe 
  and 
  arranged 
  between 
  longi- 
  

   tudinal 
  elevated 
  lines. 
  

  

  Found 
  in 
  the 
  Clinton 
  beds 
  at 
  Lock- 
  

   port 
  etc. 
  (Hall). 
  Probably 
  occurs 
  also 
  at 
  Niagara. 
  Also 
  abundant 
  

   in 
  the 
  thin 
  calcareous 
  upper 
  Medina 
  layers 
  at 
  Niagara 
  (?). 
  

  

  Fig. 
  74 
  Helopora 
  fragilis 
  natural 
  size 
  

   and 
  enlarged 
  

  

  Genus 
  clathropora 
  Hall 
  

  

  [Ety. 
  : 
  clathri, 
  a 
  lattice; 
  poms, 
  a 
  pore] 
  

  

  Zoarium 
  composed 
  of 
  anastomosing 
  branches, 
  forming 
  a 
  regular 
  

   network 
  with 
  round 
  or 
  oval 
  spaces 
  or 
  fenestrules, 
  with 
  a 
  pointed. 
  

  

  Fig. 
  75 
  Clathropora 
  frondosa 
  with 
  portions 
  of 
  celluUferous 
  face 
  enlarged 
  

  

  articulating 
  base 
  ; 
  the 
  branches 
  are 
  made 
  up 
  of 
  two 
  layers 
  grown 
  to- 
  

   gether 
  back 
  to 
  back, 
  and 
  with 
  the 
  zooecial 
  tubes 
  opening 
  on 
  both 
  

   sides 
  of 
  the 
  frond; 
  apertures 
  usually 
  subquadrate, 
  arranged 
  longi- 
  

   tudinally. 
  

  

  