﻿The 
  Fauna 
  of 
  the 
  Niagara 
  Group. 
  177 
  

  

  t$TROPHOSTYLus 
  cyolostomus 
  var. 
  disjunctus 
  n. 
  var. 
  

  

  Plate 
  30, 
  Figs. 
  14 
  and 
  15. 
  

  

  Strophostylus 
  cyclostomus? 
  Hall. 
  Doc. 
  Edit. 
  28th 
  Rep. 
  St. 
  Mus. 
  Nat. 
  Hist. 
  Ex- 
  

   planation 
  of 
  pi. 
  30, 
  figs. 
  14, 
  15. 
  1876. 
  

  

  The 
  earlier 
  volutions 
  of 
  this 
  fossil 
  have 
  the 
  characters 
  of 
  

   form 
  and 
  surface-markings 
  of 
  S. 
  cyclostomus 
  ; 
  but 
  the 
  last 
  

   volution 
  is 
  less 
  expanded, 
  and 
  becomes 
  entirely 
  disjoined 
  to- 
  

   ward 
  the 
  aperture, 
  preserving 
  no 
  evidence 
  of 
  columellar 
  lip 
  or 
  

   thickening 
  of 
  the 
  peristome. 
  

  

  The 
  surface 
  -markings 
  are 
  characteristic 
  of 
  the 
  genus. 
  

  

  BELLEROPHON 
  Montfort 
  

   Bellerophon 
  tuber. 
  

  

  Plate 
  30, 
  Figs. 
  19, 
  20. 
  

  

  Bellerophon 
  tuber 
  Hall. 
  Doc 
  Edit. 
  28th 
  Rep. 
  St. 
  Mus. 
  Nat. 
  Hist. 
  Explanation 
  

   of 
  pi. 
  30, 
  figs. 
  19, 
  20. 
  1876. 
  

  

  Shell 
  convolute, 
  subglobose, 
  height 
  and 
  width 
  about 
  equal. 
  

   Aperture 
  expanded, 
  broadly 
  reniform, 
  bilobate, 
  with 
  a 
  broad 
  

   sinus 
  on 
  the 
  dorsal 
  margin. 
  Dorsum 
  subcarinate 
  toward 
  the 
  

   aperture. 
  

  

  Surface 
  marked 
  by 
  fine 
  striae 
  parallel 
  to 
  the 
  lines 
  of 
  growth, 
  

   commencing 
  at 
  the 
  umbilicus 
  and 
  curving 
  broadly 
  over 
  the 
  

   side 
  of 
  the 
  shell, 
  and 
  somewhat 
  abruptly 
  recurved 
  on 
  the 
  

   dorsum. 
  

  

  This 
  species 
  is 
  the 
  only 
  Bellerophon 
  proper 
  which 
  has 
  come 
  

   under 
  my 
  observation 
  from 
  the 
  Niagara 
  group. 
  The 
  speci- 
  

   mens 
  of 
  this 
  species 
  from 
  Waldron 
  are 
  very 
  imperfect, 
  all 
  of 
  

   them 
  having 
  been 
  macerated, 
  and 
  usually 
  deprived 
  of 
  the 
  

   shell. 
  The 
  example 
  figured 
  is 
  less 
  expanded 
  than 
  some 
  others, 
  

   from 
  later 
  collections, 
  which 
  are 
  likewise 
  distinctly 
  carinate 
  

   on 
  the 
  dorsum 
  near 
  the 
  aperture. 
  

   18 
  

  

  