﻿362 
  Panama 
  Shells. 
  muricid^, 
  

  

  tlie 
  species 
  were 
  represented 
  by 
  few 
  individnals, 
  at 
  least 
  so 
  far 
  

   as 
  they 
  could 
  be 
  found 
  witliou.t 
  a 
  dredge. 
  A 
  similar 
  abundance 
  

   of 
  species 
  and 
  scarcity 
  of 
  specimens 
  in 
  tbis 
  genus 
  occurs 
  in 
  tbe 
  

   Caribbean 
  seas. 
  One 
  large 
  species 
  was 
  found 
  ; 
  of 
  tbe 
  others, 
  

   nearly 
  one 
  half 
  are 
  as 
  small 
  as 
  the 
  Caribbean 
  species 
  : 
  the 
  rest 
  

   are 
  nearer 
  to 
  an 
  average 
  size 
  as 
  compared 
  with 
  the 
  species 
  which 
  

   have 
  been 
  described 
  by 
  European 
  authors. 
  Most 
  of 
  the 
  small 
  

   species 
  are 
  undescribed. 
  If 
  we 
  may 
  judge 
  from 
  the 
  collections 
  

   made 
  by 
  us 
  in 
  Panama 
  and 
  in 
  Jamaica, 
  and 
  received 
  from 
  Cey- 
  

   lon, 
  it 
  may 
  be 
  conjectured 
  that 
  the 
  undescribed 
  species 
  in 
  this 
  

   genus 
  are 
  as 
  numerous 
  as 
  those 
  which 
  have 
  been 
  described. 
  

   We 
  do 
  not 
  refer 
  to 
  Kiener's 
  monograph, 
  which 
  contains 
  60 
  spe- 
  

   cies 
  : 
  for, 
  including 
  the 
  allied 
  genus 
  Mangelia, 
  nearly 
  500 
  species 
  

   have 
  been 
  described. 
  Probably 
  this 
  is 
  not 
  more 
  than 
  half 
  of 
  

   the 
  number 
  actually 
  existing. 
  

  

  163. 
  Pleiirotoma 
  aterrima. 
  

  

  Synonymy. 
  

  

  Pleurotoma 
  aterrima 
  Sowb. 
  in 
  Proc. 
  Zool. 
  Soc. 
  Lond. 
  

  

  p. 
  137. 
  Dec. 
  1833. 
  

  

  ■ 
  Mull. 
  Synop. 
  Nov. 
  Test. 
  Viv. 
  p. 
  113. 
  May 
  1836. 
  

  

  Reeve 
  Conch. 
  Icon. 
  pi. 
  12. 
  f. 
  100. 
  May 
  1843. 
  

  

  Station. 
  — 
  Under 
  stones 
  ; 
  Cuming 
  ! 
  Eeeve. 
  

   Our 
  living 
  specimens 
  were 
  found 
  in 
  the 
  same 
  situation 
  at 
  low 
  

   water 
  mark. 
  

  

  Habitat. 
  — 
  Monte 
  Christi:; 
  Cuming! 
  Sowerby 
  : 
  also 
  Eeeve. 
  

   West 
  Columbia 
  ; 
  Jay. 
  

   Panama 
  ; 
  C. 
  B. 
  A. 
  ! 
  

   We 
  collected 
  14 
  specimens, 
  most 
  of 
  which 
  were 
  occupied 
  by 
  

   hermit 
  crabs. 
  

  

  164. 
  Pletirotoma 
  atrior. 
  Nov. 
  sp. 
  

  

  Shell 
  subfusiform 
  : 
  jet 
  black, 
  with 
  a 
  paler 
  translucent 
  spiral 
  

   stripe 
  below 
  the 
  middle 
  of 
  the 
  whorls 
  : 
  with 
  a 
  spiral 
  series 
  of 
  

  

  