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  Panama 
  Shells. 
  

  

  INTRODUCTION. 
  

  

  tached 
  to 
  dead 
  shells 
  within 
  the 
  aperture, 
  render 
  it 
  one 
  of 
  

   those 
  which 
  are 
  least 
  exposed 
  to 
  such 
  accidents. 
  

  

  The 
  following 
  is 
  a 
  list 
  of 
  the 
  principal 
  pairs 
  of 
  analogues 
  

   which 
  inhabit 
  both 
  sides 
  of 
  the 
  Isthmus. 
  The 
  list 
  might 
  be 
  

   increased, 
  especially 
  by 
  comparision 
  of 
  the 
  very 
  minute 
  

   species. 
  But 
  the 
  group, 
  as 
  it 
  is, 
  presents 
  such 
  a 
  variety 
  in 
  

   respect 
  of 
  size 
  and 
  characters, 
  of 
  habits 
  of 
  station, 
  tenacity 
  of 
  

   life, 
  &c., 
  as 
  to 
  render 
  it 
  incredible 
  that 
  they 
  all 
  should 
  owe 
  

   their 
  distribution 
  in 
  pairs 
  to 
  a 
  common 
  process 
  of 
  transporta- 
  

   tion. 
  Cyprsea 
  cervinetta 
  occurs 
  only 
  beneath 
  large 
  rocks, 
  at 
  the 
  

   low 
  water 
  mark 
  of 
  the 
  spring 
  tides, 
  and 
  lives 
  but 
  a 
  short 
  

   time 
  when 
  removed 
  from 
  the 
  water, 
  and 
  Strombus 
  gracilior 
  

   is 
  pelagic 
  ; 
  and 
  the 
  others 
  live 
  at 
  or 
  near 
  low 
  water 
  mark 
  

   on 
  rocks, 
  under 
  stones, 
  in 
  sand, 
  in 
  fine 
  mud, 
  &c. 
  In 
  gene- 
  

   ral 
  the 
  derivation 
  of 
  analogues 
  from 
  a 
  common 
  stock 
  is 
  more- 
  

   over 
  inconsistent 
  with 
  the 
  existence 
  of 
  analogues 
  which 
  are 
  

   antipodes 
  to 
  each 
  other. 
  

  

  Panama. 
  

  

  Cypreea 
  cervinetta 
  ; 
  

   Marginella 
  minor 
  ; 
  

   M. 
  sapotilla 
  ; 
  

   Mitra 
  nucleola 
  ; 
  

   Oliva 
  araneosa 
  ; 
  

   0. 
  venulata 
  ; 
  

   Purpura 
  undata 
  ; 
  ' 
  

  

  Columbella 
  guttata 
  ; 
  

  

  Cassis 
  abbreviata 
  ; 
  

   Oniscia 
  tuberculosa 
  ; 
  

   Strombus 
  gracilior 
  : 
  

   Triton 
  vestitus 
  ; 
  

   Murex 
  erosus 
  ; 
  

   Pyrula 
  patula 
  ; 
  

  

  *Jamaica. 
  

  

  C. 
  exanthema. 
  

  

  M. 
  minima. 
  

  

  M. 
  prunum. 
  

  

  M. 
  granulosa. 
  

  

  0. 
  reticulata. 
  

  

  0. 
  scripta. 
  

  

  P. 
  fasciata. 
  

  

  C. 
  cribraria 
  Lam. 
  

  

  C. 
  parvula 
  Dunker.. 
  

  

  C. 
  inflata. 
  

  

  0. 
  oniscus. 
  

  

  S. 
  pugilis. 
  

  

  T. 
  pilearis. 
  

  

  M. 
  intermedius. 
  

  

  P. 
  melonofena. 
  

  

  » 
  These 
  Oariibbeaa 
  species 
  have 
  all 
  been 
  collected 
  by 
  us 
  in 
  Jamaica. 
  

  

  