﻿176 
  Twenty-eighth 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  ally 
  increasing 
  in 
  size 
  from 
  the 
  apex, 
  the 
  last 
  volution 
  free 
  for 
  

   a 
  short 
  distance 
  above 
  the 
  aperture, 
  the 
  back 
  sometimes 
  flat- 
  

   tened 
  ; 
  aperture 
  broadly 
  elliptical, 
  opening 
  nearly 
  parallel 
  

   to 
  the 
  axis 
  of 
  the 
  shell, 
  without 
  proper 
  umbilicus 
  ; 
  suture-line 
  

   deeply 
  impressed 
  leaving 
  more 
  than 
  three-fourths 
  of 
  the 
  

   height 
  of 
  the 
  volution 
  exposed. 
  

  

  Surface 
  marked 
  by 
  fine 
  transverse 
  striae 
  of 
  growth, 
  which 
  

   are 
  usually 
  quite 
  regular, 
  but 
  sometimes 
  abruptly 
  arching 
  for- 
  

   ward 
  on 
  the 
  middle 
  of 
  the 
  last 
  volution, 
  and 
  receding 
  above 
  

   and 
  below, 
  in 
  conformity 
  to 
  sinuosities 
  in 
  the 
  lip. 
  

  

  This 
  species 
  is 
  distinguished 
  from 
  P. 
  Niagarense 
  by 
  the 
  

   more 
  elevated 
  spire, 
  and 
  by 
  the 
  form 
  and 
  relative 
  position 
  of 
  

   the 
  aperture. 
  The 
  surface 
  -markings 
  are 
  also 
  usually 
  finer 
  

   than 
  in 
  that 
  species. 
  

  

  STROPHOSTYLUS 
  Hall. 
  

   Stkophostylus 
  cyclostomus. 
  

  

  Plate 
  30, 
  Figs. 
  1-13. 
  

  

  Strophostylus 
  cyclostomus 
  Hall. 
  Trans. 
  Alb. 
  Inst., 
  vol. 
  iv, 
  p. 
  218. 
  Abstract 
  

   p. 
  24 
  ; 
  May, 
  1863. 
  

  

  Shell 
  subglobose 
  or 
  transversely 
  broad 
  oval. 
  Spire 
  moder- 
  

   ately 
  elevated 
  ; 
  volutions 
  about 
  four, 
  rounded, 
  the 
  last 
  one 
  

   extremely 
  ventricose 
  and 
  very 
  much 
  extended 
  on 
  the 
  upper 
  

   side 
  and 
  at 
  the 
  sutural 
  margin. 
  Aperture 
  circular 
  or 
  subcir- 
  

   cular, 
  very 
  oblique 
  to 
  the 
  axis 
  ; 
  peristome 
  thin, 
  entire, 
  with- 
  

   out 
  sinus 
  or 
  emargination, 
  spreading 
  over 
  the 
  surface 
  of 
  the 
  

   next 
  volution, 
  rarely 
  leaving 
  a 
  slight 
  umbilicus. 
  Columellar 
  

   lip 
  grooved 
  in 
  the 
  lower 
  part, 
  with 
  a 
  rather 
  strong 
  spiral 
  fold 
  

   at 
  about 
  one- 
  third 
  the 
  diameter 
  from 
  the 
  lower 
  side 
  of 
  the 
  

   aperture. 
  Suture 
  not 
  canaliculate. 
  

  

  Surface 
  marked 
  by 
  strong, 
  crowded 
  lamellose 
  striae 
  of 
  

   growth 
  parallel 
  to 
  the 
  margin 
  of 
  the 
  aperture, 
  and 
  by 
  much 
  

   finer 
  revolving, 
  undulating 
  lines, 
  producing 
  a 
  finely 
  cancellate 
  

   structure 
  in 
  well-preserved 
  specimens. 
  

  

  This 
  species, 
  in 
  the 
  elevation 
  of 
  the 
  spire, 
  differs 
  from 
  any 
  

   other 
  described 
  form 
  of 
  the 
  genus, 
  except 
  8. 
  elegans 
  of 
  the 
  

   Lower 
  Helderberg, 
  and 
  from 
  that 
  one 
  in 
  being 
  more 
  ventricose 
  

   and*more 
  oblique. 
  

  

  