﻿NIAGARA 
  FALLS 
  AND 
  VICINITY 
  211 
  

  

  Genus 
  platyceras 
  Conrad 
  

  

  [Ety. 
  : 
  TzXarb^, 
  flat; 
  y.ipa^, 
  horn] 
  

  

  (1840. 
  An. 
  rep't 
  pal. 
  N. 
  Y. 
  p. 
  205) 
  

  

  Shell 
  conic, 
  irregular, 
  with 
  or 
  without 
  the 
  apex 
  inrolled; 
  aperture 
  

   expanded, 
  often 
  reflexed; 
  peristome 
  entire, 
  often 
  sinuous; 
  surface 
  

   variously 
  striated, 
  sometimes 
  bearing 
  spines. 
  

  

  Platyceras 
  niagarense 
  (Hall) 
  (Fig. 
  139). 
  

   Acroculia 
  niagarensis 
  Hall 
  (1852. 
  

   Pal.N. 
  7.2:288, 
  pi. 
  60) 
  

  

  Distinguishing 
  characters. 
  Involute 
  apex, 
  

   scarcely 
  forming 
  a 
  . 
  volution 
  ; 
  gradually 
  ex- 
  

   panding 
  lower 
  portion, 
  with 
  two 
  or 
  three 
  

   longitudinal 
  folds 
  or 
  undulations; 
  transverse 
  

   striae, 
  which 
  undulate 
  across 
  the 
  folds 
  and 
  

  

  1 
  . 
  Fig. 
  139 
  Platyceras 
  n'agarense 
  

  

  depressions. 
  

  

  Found 
  rarely 
  in 
  the 
  lower 
  Rochester 
  shale 
  at 
  Niagara. 
  Also 
  at 
  

   Lockport 
  (Hall). 
  

  

  Platyceras 
  angulatum 
  (Hall) 
  (Fig. 
  140). 
  Acroculia 
  an- 
  

   g 
  u 
  1 
  a 
  t 
  a 
  Hall 
  (1852. 
  Pal. 
  N. 
  Y. 
  2:289, 
  pl- 
  60) 
  

  

  Distingtiishing 
  characters. 
  Attenuated 
  apex, 
  form- 
  

   ing 
  one 
  or 
  two 
  minute 
  volutions; 
  shell 
  below 
  extend- 
  

   ing 
  in 
  a 
  broad 
  curve, 
  and 
  expanding 
  rapidly 
  toward 
  

   the 
  aperture, 
  which 
  is 
  much 
  dilated; 
  angulated 
  sur- 
  

   face, 
  with 
  a 
  sharp 
  carina 
  on 
  the 
  upper 
  and 
  lower 
  outer 
  

   Fig. 
  140 
  Platyceras 
  margins, 
  and 
  an 
  obtuse 
  carina 
  in 
  the 
  middle; 
  trans- 
  

  

  angulatum 
  

  

  verse 
  section 
  unequally 
  pentagonal. 
  

   Found 
  in 
  the 
  lower 
  and 
  middle 
  Rochester 
  shale 
  at 
  Niagara. 
  

   Rare. 
  Also 
  at 
  Lockport 
  (Hall). 
  

  

  Genus 
  diaphorostoma 
  Fischer 
  

  

  [Ety.: 
  dtd<p()po?, 
  unlike; 
  ^T 
  Of 
  j.a, 
  mouth] 
  

  

  (1885. 
  Manual 
  de 
  Conchyliologie; 
  Platyostoma 
  Conrad. 
  

  

  1842. 
  Acad. 
  nat. 
  sci. 
  Jour. 
  8:275) 
  

  

  Shell 
  with 
  a 
  short 
  depressed 
  spire, 
  a 
  large 
  dilated 
  aperture 
  and 
  

   with 
  the 
  inner 
  lip 
  lying 
  close 
  against 
  the 
  body 
  whorl. 
  

  

  