﻿404 
  Panama 
  Shells. 
  littorinid.e. 
  

  

  249. 
  Rissoa 
  notabilis. 
  Nov. 
  sp. 
  

  

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

   fourteen 
  transverse 
  very 
  prominent 
  ribs, 
  which 
  have 
  concave 
  

   summits 
  ; 
  with 
  four 
  spiral 
  keels, 
  of 
  which 
  the 
  upper 
  two 
  are 
  

   more 
  distant 
  and 
  are 
  seen 
  on 
  the 
  spire 
  on 
  each 
  side 
  of 
  the 
  

   suture 
  ; 
  the 
  transverse 
  ribs 
  are 
  smaller 
  in 
  the 
  parts 
  between 
  the 
  

   second 
  and 
  third 
  keels, 
  and 
  are 
  obsolete 
  below 
  the 
  third 
  : 
  apex 
  

   subobtuse, 
  smooth 
  and 
  shining 
  : 
  spire 
  with 
  the 
  outlines 
  recti- 
  

   linear 
  except 
  near 
  the 
  apex 
  : 
  whorls 
  six, 
  abruptly 
  shouldered, 
  

   planulate, 
  with 
  the 
  suture 
  subcanaliculate 
  : 
  aperture 
  ovate 
  : 
  

   umbilicus 
  wanting. 
  

  

  Mean 
  divergence 
  about 
  24° 
  ; 
  length 
  .06 
  inch 
  ; 
  breadth 
  .027 
  

   inch. 
  

  

  Station. 
  — 
  Unknown. 
  

  

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

   1 
  specimen 
  was 
  found. 
  

  

  250. 
  Rissoa 
  ^calarilbrmis. 
  Nov. 
  sp. 
  

  

  Shell 
  elongate, 
  ovate 
  conic 
  : 
  dingy 
  white 
  : 
  with, 
  on 
  each 
  

   whorl, 
  eleven 
  stout 
  prominent 
  acute 
  compressed 
  ribs, 
  which 
  are 
  

   continuous 
  on 
  the 
  successive 
  whorls 
  ; 
  covered 
  with 
  microscopic 
  

   spiral 
  strife, 
  which 
  ascend 
  the 
  sides 
  of 
  the 
  ribs 
  but 
  are 
  obsolete 
  

   on 
  their 
  summits 
  : 
  apex 
  acute 
  : 
  spire 
  with 
  the 
  outlines 
  mode- 
  

   rately 
  curved 
  : 
  whorls 
  eight, 
  convex, 
  with 
  a 
  well 
  impressed 
  

   suture 
  : 
  aperture 
  obliquely 
  ovate, 
  effuse 
  above 
  and 
  below 
  : 
  

   labrum 
  moderately 
  thickened, 
  well 
  excurved 
  and 
  produced 
  

   along 
  the 
  middle. 
  

  

  Mean 
  divergence 
  about 
  33° 
  ; 
  length 
  .13 
  inch 
  ; 
  breadth 
  .05 
  

   inch 
  ; 
  length 
  of 
  spire 
  .08 
  inch. 
  

  

  Station. 
  — 
  Unknown. 
  

  

  Habitat 
  — 
  Panama 
  ; 
  C. 
  B. 
  A. 
  ! 
  

   1 
  specimen 
  was 
  found 
  in 
  sand. 
  

  

  