﻿402 
  Panama 
  Shells. 
  littorinidtE. 
  

  

  245. 
  Rissoa 
  fortis. 
  Nov. 
  sp. 
  

  

  Shell 
  long, 
  ovate 
  conic 
  : 
  white 
  : 
  with, 
  on 
  each 
  whorl, 
  about 
  

   twenty-two 
  to 
  twenty-four 
  stout 
  prominent 
  approximate 
  ribs, 
  

   which 
  converge 
  at 
  the 
  anterior 
  extremit}'', 
  where 
  they 
  become 
  

   very 
  small 
  : 
  apex 
  acute 
  : 
  spire 
  with 
  the 
  outlines 
  curvilinear 
  : 
  

   whorls 
  ten, 
  slightly 
  shouldered, 
  moderately 
  convex, 
  with 
  a 
  well 
  

   impressed 
  suture 
  ; 
  last 
  whorl 
  ventricose 
  : 
  aperture 
  oblique, 
  

   ovate, 
  retreating 
  above, 
  deeply 
  effuse 
  : 
  labrum 
  much 
  advanced 
  

   in 
  the 
  lower 
  half, 
  very 
  thick 
  : 
  labium 
  thick 
  : 
  umbilicus 
  want- 
  

   ing. 
  

  

  Mean 
  divergence 
  about 
  33° 
  ; 
  length 
  .29 
  inch 
  ; 
  breadth 
  .12 
  

   inch 
  ; 
  length 
  of 
  spire 
  .185 
  inch. 
  

  

  This 
  species 
  resembles 
  R. 
  amhigua 
  Gould, 
  and 
  is 
  very 
  different 
  

   from 
  Rissoina 
  Inca 
  Orb. 
  

  

  Station. 
  — 
  Under 
  stones 
  near 
  low 
  water 
  mark. 
  

  

  //a&^■^a^.— 
  Taboga 
  ; 
  C. 
  B. 
  A. 
  ! 
  

   31 
  specimens 
  were 
  collected. 
  

  

  246. 
  Ris§oa 
  (?) 
  incon^picua. 
  Nov. 
  sp. 
  

  

  Shell 
  ovate 
  conic 
  : 
  white 
  : 
  with 
  several 
  spiral 
  ridges, 
  of 
  which 
  

   two 
  or 
  three 
  are 
  seen 
  on 
  the 
  spire 
  : 
  with 
  about 
  twelve 
  or 
  four- 
  

   teen 
  transverse 
  narrow 
  ridges, 
  which 
  are 
  obsolete 
  anteriorly: 
  

   apex 
  subacute 
  : 
  spire 
  with 
  curvilinear 
  outlines 
  : 
  whorls 
  four, 
  

   very 
  convex, 
  with 
  a 
  deep 
  suture 
  : 
  last 
  whorl 
  rather 
  ventricose, 
  

   short 
  : 
  aperture 
  orbicular, 
  scarcely 
  effuse 
  : 
  lip 
  well 
  thickened 
  : 
  

   with 
  a 
  very 
  minute 
  umbilicus. 
  Perhaps 
  this 
  species 
  should 
  

   have 
  been 
  referred 
  to 
  Cingula. 
  

  

  Mean 
  divergence 
  about 
  55° 
  ; 
  length 
  ,045 
  inch 
  : 
  breadth 
  .03 
  

   inch 
  ; 
  length 
  of 
  spire 
  .032 
  inch. 
  

  

  Station. 
  — 
  Unknown. 
  

  

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

   1 
  specimen 
  was 
  obtained. 
  

  

  