﻿268 
  Panama 
  Shells: 
  mitrid^. 
  

  

  between 
  these 
  species. 
  We 
  will 
  venture 
  to 
  add 
  that 
  while 
  

   the 
  species 
  are 
  clearly 
  distinct, 
  they 
  constitute 
  one 
  of 
  those 
  

   interesting 
  pairs 
  of 
  analogues, 
  which 
  inhabit 
  opposite 
  sides 
  of 
  

   the 
  Isthmus 
  of 
  tropical 
  America. 
  

  

  M. 
  granulosa 
  we 
  believe 
  to 
  be 
  exclusively 
  a 
  Caribbean 
  

   species, 
  although 
  Kiener 
  says 
  " 
  Habite 
  les 
  niers 
  de 
  I'Inde 
  et 
  

   de 
  la 
  Nouvelle 
  Zelande, 
  de 
  la 
  Guadeloupe, 
  de 
  la 
  Trinite 
  et 
  du 
  

   Mexique." 
  

  

  19. 
  mitra 
  solitarla. 
  Nov. 
  sp. 
  

  

  Shell 
  rather 
  slender, 
  fusiform 
  : 
  of 
  a 
  very 
  deep 
  blackish 
  

   brown, 
  less 
  deep 
  in 
  the 
  aperture, 
  and 
  quite 
  pale 
  on 
  the 
  plaits 
  : 
  

   with 
  very 
  numerous 
  small 
  transverse 
  ribs, 
  which 
  are 
  obsolete 
  

   anteriorly, 
  and 
  which 
  are 
  granulated 
  by 
  revolving 
  strise, 
  that 
  

   are 
  obsolete 
  in 
  the 
  interspaces 
  posteriorly, 
  and 
  are 
  strongly 
  de- 
  

   veloped 
  anteriorly, 
  with 
  microscopic 
  incremental 
  striae 
  ; 
  apex 
  

   acute 
  : 
  whorls 
  ten, 
  moderately 
  convex, 
  slightly 
  shouldered 
  

   above, 
  with 
  a 
  moderately 
  impressed 
  suture 
  : 
  aperture 
  long, 
  

   with 
  a 
  rather 
  short 
  canal 
  : 
  labrum 
  thick, 
  with 
  numerous 
  sharp 
  

   plaits 
  inside, 
  with 
  a 
  sinus 
  near 
  the 
  posterior 
  end 
  : 
  columella 
  

   with 
  four 
  plaits. 
  Length 
  .68 
  inch 
  ; 
  breadth, 
  .23 
  inch 
  ; 
  length 
  

   of 
  aperture, 
  .34 
  inch. 
  

  

  Station. 
  — 
  Under 
  stones 
  near 
  low 
  water 
  mark 
  we 
  found 
  this 
  

   elegant 
  and 
  rare 
  shell. 
  

  

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

  

  We 
  found 
  a 
  single 
  specimen 
  on 
  the 
  reef. 
  

  

  20. 
  Mitra 
  tristis^. 
  

  

  Synonymy. 
  

  

  Mitra 
  tristis 
  Bred, 
  in 
  Proc. 
  Zool. 
  See. 
  Lend. 
  p. 
  194, 
  Dec. 
  1835. 
  

   Reeve 
  Conch. 
  Icon. 
  ]A. 
  15. 
  f. 
  114. 
  Sept. 
  1844. 
  

  

  Station. 
  — 
  In 
  sandy 
  mud 
  at 
  the 
  depth 
  of 
  6 
  to 
  10 
  fathoms 
  ; 
  

   Cuming 
  ! 
  Broderip 
  ; 
  also 
  Reeve. 
  We 
  found 
  sev- 
  

  

  