﻿New 
  Species 
  of 
  Stoastoma. 
  65 
  

  

  ed 
  : 
  umbilicus 
  rather 
  wide, 
  with 
  the 
  spiral 
  lamella 
  moderately 
  

   developed. 
  Operculum 
  very 
  deeply 
  concave, 
  auriculate 
  at 
  

   both 
  extremities, 
  very 
  finely 
  punctulate. 
  

  

  Mean 
  divergence 
  about 
  140° 
  ; 
  height 
  .035 
  inch 
  ; 
  greatest 
  

   breadth 
  .07 
  inch 
  ; 
  least 
  breadth 
  .055 
  inch. 
  

  

  This 
  species 
  closely 
  resembles 
  S. 
  Gouldiamim, 
  and 
  is 
  most 
  

   readily 
  distinguished 
  by 
  the 
  difference 
  in 
  size. 
  A 
  closer 
  in- 
  

   spection 
  will 
  detect 
  the 
  more 
  essential 
  differences. 
  

  

  Stoastoma 
  Tappanianum. 
  Shell 
  subdiscoidal 
  : 
  pale 
  horn 
  

   color, 
  subtransparent 
  : 
  with 
  seven 
  spiral 
  carinee, 
  of 
  which 
  the 
  

   upper 
  one 
  is 
  small 
  and 
  the 
  lower 
  one 
  very 
  minute, 
  and 
  of 
  

   which 
  two 
  are 
  visible 
  on 
  the 
  upper 
  whorls 
  ; 
  with 
  very 
  deli- 
  

   cate 
  spiral 
  raised 
  lines, 
  usually 
  one 
  between 
  the 
  first 
  pair 
  of 
  

   carinEB 
  and 
  two 
  or 
  three 
  in 
  each 
  following 
  interspace 
  : 
  spire 
  

   moderately 
  and 
  convexly 
  elevated 
  : 
  whorls 
  three 
  and 
  one-half, 
  

   moderately 
  convex, 
  with 
  a 
  deep 
  suture 
  ; 
  last 
  whorl 
  scarcely 
  

   detached 
  from 
  the 
  penult 
  whorl 
  near 
  the 
  aperture 
  : 
  aperture 
  

   rather 
  more 
  than 
  a 
  semicircle, 
  a 
  little 
  contracted 
  behind 
  the 
  

   labrum, 
  which 
  is 
  well 
  produced, 
  above 
  rather 
  abruptly 
  pro= 
  

   duced, 
  scarcely 
  modified 
  by 
  the 
  carinse 
  ; 
  labium 
  much 
  de- 
  

   tached 
  from 
  the 
  penult 
  whorl 
  and 
  a 
  little 
  reflected 
  : 
  umbilicus 
  

   rather 
  wide, 
  with 
  the 
  spiral 
  lamella 
  moderately 
  developed. 
  

   Operculum 
  very 
  deeply 
  concave 
  externally, 
  smooth, 
  auriculate 
  

   at 
  both 
  extremities. 
  

  

  Mean 
  divergence 
  about 
  140° 
  ; 
  height 
  .045 
  inch 
  ; 
  greatest 
  

   breadth 
  .086 
  inch 
  ; 
  least 
  breadth 
  .07 
  inch. 
  

  

  This 
  shell 
  also 
  resembles 
  S. 
  GoulcUcmum, 
  and 
  might 
  be 
  

   mistaken 
  for 
  the 
  young 
  of 
  that 
  species. 
  But 
  the 
  labrum 
  is 
  

   thickened 
  as 
  in 
  all 
  mature 
  shells 
  of 
  Stoastoma 
  proper. 
  It 
  is 
  

   most 
  readily 
  distinguished 
  from 
  that 
  species 
  by 
  the 
  peculiari- 
  

   ties 
  of 
  the 
  aperture. 
  

  

  Stoastoma 
  Hollandianum. 
  Shell 
  subdiscoidal 
  : 
  pale 
  horn 
  

  

  