﻿The 
  Fauna 
  of 
  the 
  Niagara 
  Group. 
  123 
  

  

  * 
  

  

  FENESTELLA 
  Lonsdale. 
  

  

  Fenestella 
  ambigtja 
  n. 
  sp. 
  

  

  Plate 
  11, 
  Figs. 
  17-21. 
  

  

  Hemitrypa 
  dubia 
  Hall. 
  Doc. 
  Edit. 
  28th 
  Rep. 
  St. 
  Mus. 
  Nat. 
  Hist. 
  Explana- 
  

   tion 
  of 
  pi. 
  11, 
  figs. 
  17-21. 
  1876. 
  

   Not 
  Fenestella 
  dubia 
  Lonsdale. 
  

  

  Bryozoum 
  broadly 
  funnel-form 
  ; 
  branches, 
  eight 
  in 
  the 
  

   space 
  of 
  ^ve 
  millimetres 
  ; 
  on 
  the 
  non-poriferous 
  side 
  regular 
  

   and 
  somewhat 
  rigid 
  in 
  appearance, 
  flattened, 
  striated 
  ; 
  striae 
  

   sharp, 
  slightly 
  sinuous 
  and 
  sometimes 
  granulose, 
  two 
  to 
  three 
  

   on 
  each 
  branch. 
  Dissepiments 
  strong, 
  frequently 
  as 
  wide 
  as 
  

   the 
  branches, 
  six 
  in 
  the 
  space 
  of 
  iive 
  millimetres, 
  expanding 
  at 
  

   their 
  junction 
  with 
  the 
  branches 
  and 
  on 
  the 
  same 
  plane 
  ; 
  stri- 
  

   ated 
  on 
  the 
  non 
  -poriferous 
  side. 
  Fenestrules 
  oval 
  to 
  subcir- 
  

   cular, 
  from 
  nearly 
  equal 
  to 
  twice 
  the 
  width 
  of 
  the 
  branches, 
  

   and 
  from 
  one-third 
  longer 
  to 
  nearly 
  twice 
  as 
  long 
  as 
  wide. 
  

  

  Cell-apertures 
  in 
  two 
  ranges, 
  small, 
  circular, 
  separated 
  

   from 
  each 
  other 
  by 
  a 
  distance 
  greater 
  than 
  the 
  aperture, 
  

   four 
  in 
  each 
  fenestrule, 
  opening 
  nearly 
  directly 
  upward, 
  with 
  

   a 
  distinctly 
  elevated 
  margin. 
  Ranges 
  of 
  cellules 
  separated 
  by 
  

   a 
  thin 
  partition 
  which 
  extends 
  upward 
  to 
  an 
  elevation 
  equal 
  

   to 
  twice 
  the 
  thickness 
  of 
  the 
  branch 
  below, 
  and 
  then 
  expand- 
  

   ing 
  laterally 
  on 
  each 
  side, 
  forms 
  a 
  pseudo-branch. 
  These 
  

   pseudo-branches 
  are 
  connected 
  by 
  dissepiments 
  which 
  arise 
  

   from 
  the 
  upward 
  growth 
  and 
  expansion 
  of 
  the 
  narrow 
  edges 
  of 
  

   the 
  dissepiments 
  below, 
  in 
  the 
  same 
  manner 
  as 
  in 
  the 
  branches 
  

   proper, 
  and 
  the 
  surface 
  of 
  both 
  the 
  pseudo-branches 
  and 
  dissep- 
  

   iments 
  are 
  striated 
  as 
  on 
  the 
  non 
  -poriferous 
  face. 
  In 
  well-pre- 
  

   served 
  specimens 
  there 
  are 
  rows 
  of 
  minute 
  pits 
  between 
  the 
  

   striae. 
  This 
  accessory 
  surface 
  differs, 
  however, 
  in 
  some 
  degree 
  

   from 
  the 
  non-poriferous 
  face 
  proper, 
  in 
  the 
  apparently 
  more 
  

   sinuous 
  character 
  and 
  irregularity 
  of 
  growth 
  in 
  branches 
  and 
  

   dissepiments, 
  giving 
  a 
  different 
  aspect 
  to 
  the 
  fenestrules. 
  

  

  Fenestella 
  parvulipora. 
  

  

  Plate 
  12, 
  Figs. 
  1-9. 
  

  

  Fenestella 
  parvulipora 
  Hall. 
  Doc. 
  Edit. 
  28th 
  Rep. 
  St. 
  Mus. 
  Nat. 
  Hist. 
  Explana- 
  

   tion 
  of 
  pi. 
  12, 
  figs. 
  1-9. 
  1876. 
  

  

  Frond 
  broadly 
  funnel-shaped, 
  and 
  growing 
  very 
  luxuri- 
  

  

  