﻿PLATE 
  XXIX. 
  

  

  PLATYOSTOMA 
  NlAGAREtfSE 
  Hall. 
  

  

  Page 
  175. 
  

  

  Figs. 
  1-4. 
  Four 
  views 
  of 
  a 
  specimen 
  of 
  medium 
  size, 
  where 
  the 
  inner 
  lip 
  of 
  the 
  

  

  peristome 
  unites 
  with 
  the 
  surface 
  of 
  the 
  preceding 
  volution, 
  with 
  

  

  the 
  spire 
  rising 
  but 
  little 
  above 
  the 
  level 
  of 
  the 
  outer 
  part 
  of 
  the 
  

  

  shell. 
  

  

  Fig. 
  5. 
  The 
  aperture 
  of 
  a 
  specimen 
  having 
  the 
  spire 
  flat 
  or 
  slightly 
  depressed, 
  

   and 
  the 
  peristome 
  spreading 
  upon, 
  and 
  conforming 
  to, 
  the 
  shape 
  of 
  

   the 
  preceding 
  volution. 
  

  

  Fig. 
  6. 
  The 
  aperture 
  of 
  a 
  larger 
  specimen, 
  with 
  more 
  rounded 
  volutions 
  and 
  

   elevated 
  spire, 
  but 
  having 
  the 
  peristome 
  overlapping 
  the 
  preceding 
  

   volution. 
  

  

  Figs. 
  7-10. 
  Four 
  views 
  of 
  a 
  specimen 
  with 
  moderately 
  elevated 
  spire, 
  sub- 
  

   depressed 
  volutions 
  and 
  slightly 
  united 
  peristome. 
  In 
  consequence 
  

   of 
  some 
  accident 
  during 
  the 
  early 
  stages 
  of 
  growth, 
  the 
  inner 
  part 
  

   of 
  the 
  lower 
  lip 
  has 
  become 
  contracted, 
  forming 
  a 
  deep 
  and 
  abrupt 
  

   break 
  in 
  the 
  margin, 
  which 
  has 
  probably 
  increased 
  with 
  the 
  age 
  

   of 
  the 
  shell 
  ; 
  as 
  shown 
  in 
  fig. 
  9. 
  

  

  Figs. 
  11-13. 
  Front, 
  dorsal 
  and 
  basal 
  views 
  of 
  a 
  slender, 
  depressed 
  specimen, 
  

   with 
  loosely 
  coiled 
  volutions, 
  which 
  become 
  disunited 
  and 
  deflected. 
  

  

  Figs. 
  14, 
  15. 
  The 
  opposite 
  sides 
  of 
  a 
  large 
  ventricose 
  specimen, 
  with 
  rapidly 
  

   increasing 
  volutions 
  — 
  the 
  last 
  one 
  becoming 
  disunited 
  and 
  de- 
  

   flected, 
  presenting 
  a 
  very 
  peculiar 
  character, 
  and 
  wide 
  contrast 
  

   with 
  other 
  forms. 
  

  

  