﻿388 
  Panama 
  Shells. 
  littorinid^. 
  

  

  Habitat. 
  — 
  Panama 
  ; 
  C. 
  B. 
  A. 
  ! 
  

   2 
  specimens 
  were 
  found. 
  

  

  CHEIfllVITZIA.— 
  The 
  following 
  species 
  of 
  this 
  genus, 
  

   with 
  the 
  exception 
  of 
  C. 
  communis 
  and 
  C. 
  emarginata, 
  have 
  the 
  

   axis 
  of 
  the 
  first 
  whorl 
  nearly 
  or 
  quite 
  perpendicular 
  to 
  the 
  axis 
  

   of 
  the 
  other 
  whorls, 
  constituting 
  a 
  subacute, 
  subtransparent, 
  

   smooth 
  and 
  colorless 
  apex. 
  This 
  remark, 
  however, 
  cannot 
  yet 
  

   be 
  apphed 
  to 
  C. 
  major, 
  the 
  unique 
  specimen 
  of 
  which 
  has 
  lost 
  

   the 
  apex. 
  

  

  As 
  in 
  Vitrinella 
  and 
  in 
  some 
  other 
  groups 
  of 
  minute 
  tropical 
  

   species, 
  the 
  number 
  of 
  individuals 
  is 
  small 
  in 
  proportion 
  to 
  the 
  

   number 
  of 
  species. 
  The 
  following 
  12 
  species 
  are 
  represented 
  

   by 
  129 
  specimens, 
  of 
  which 
  90 
  belong 
  to 
  one 
  species, 
  and 
  21 
  

   others 
  belong 
  to 
  2 
  species, 
  leaving 
  9 
  species 
  represented 
  by 
  only 
  

   18 
  specimens. 
  

  

  219. 
  Cheinnitzia 
  aculeus. 
  Nov. 
  sp. 
  

  

  Shell 
  conic, 
  very 
  slender 
  : 
  white 
  : 
  with, 
  on 
  each 
  whorl, 
  about 
  

   seventeen 
  obtuse 
  ribs, 
  which 
  terminate 
  abruptly 
  at 
  the 
  periphery 
  

   of 
  the 
  last 
  whorl 
  : 
  spire 
  with 
  the 
  outhnes 
  rectihnear 
  except 
  near 
  

   the 
  apex 
  : 
  whorls 
  twelve, 
  moderately 
  convex, 
  with 
  a 
  well 
  im- 
  

   pressed 
  suture; 
  last 
  whorl 
  with 
  the 
  periphery 
  subangular: 
  

   aperture 
  subovate 
  : 
  labrum 
  thin 
  : 
  columella 
  scarcely 
  curved 
  : 
  

   umbilicus 
  wanting. 
  

  

  Mean 
  divergence 
  about 
  13°; 
  length 
  .18 
  inch; 
  breadth 
  .04 
  

   inch 
  ; 
  length 
  of 
  spire 
  .145 
  inch. 
  

  

  Station. 
  — 
  Unknown. 
  

  

  Habitat. 
  — 
  Panama 
  ; 
  C. 
  B. 
  A. 
  ! 
  

  

  4 
  specimens 
  were 
  found 
  in 
  the 
  sand. 
  

  

  220. 
  Chemnitzia 
  acuminata. 
  Nov. 
  sp. 
  

  

  Shell 
  fusiform 
  conic 
  : 
  dingy 
  white 
  : 
  with 
  about 
  sixteen 
  or 
  

   eighteen 
  transverse 
  somewhat 
  oblique 
  ribs, 
  which 
  terminate 
  ab- 
  

  

  