﻿INTRODUCTION. 
  Panama 
  Shells. 
  245 
  

  

  are 
  about 
  sixteen 
  to 
  twenty 
  feet. 
  The 
  difference 
  be- 
  

   tween 
  the 
  spring 
  tides 
  and 
  the 
  neap 
  tides 
  amounts 
  to 
  from 
  

   four 
  to 
  six 
  feet. 
  Hence 
  at 
  the 
  low 
  water 
  mark 
  of 
  two 
  or 
  three 
  

   tides, 
  once 
  each 
  fortnight, 
  species 
  of 
  shells, 
  as 
  well 
  as 
  of 
  

   Echinoderms 
  and 
  other 
  animals, 
  may 
  beobtained, 
  which 
  can- 
  

   not 
  be 
  procured 
  at 
  any 
  other 
  time 
  except 
  by 
  dredging. 
  Other 
  

   species 
  live 
  where 
  every 
  tide 
  will 
  leave 
  them 
  exposed 
  to 
  the 
  

   air 
  for 
  a 
  short 
  time. 
  All 
  the 
  way 
  from 
  low 
  water 
  mark, 
  up 
  

   to 
  the 
  ledges 
  of 
  rocks 
  where 
  some 
  species 
  of 
  Littorina 
  live 
  out 
  

   of 
  the 
  reach 
  of 
  the 
  highest 
  tides, 
  species 
  are 
  found, 
  most 
  of 
  

   which 
  are 
  limited 
  to 
  a 
  very 
  narrow 
  vertical 
  zone. 
  The 
  sur- 
  

   face 
  in 
  front 
  of 
  the 
  city, 
  which 
  is 
  left 
  bare 
  by 
  the 
  recess 
  of 
  

   the 
  tide, 
  extends 
  out 
  half 
  a 
  mile 
  or 
  more. 
  Thus 
  over 
  several 
  

   square 
  miles 
  the 
  secrets 
  of 
  the 
  ocean 
  maybe 
  explored. 
  

  

  The 
  bay 
  of 
  Panama 
  contains 
  several 
  beautiful 
  islands, 
  

   "which 
  rise 
  as 
  steep 
  mountains 
  directly 
  from 
  the 
  water's 
  edge. 
  

   One 
  of 
  these 
  is 
  Taboga,* 
  12 
  miles 
  from 
  Panama, 
  from 
  and 
  to 
  

   which 
  a 
  small 
  American 
  steamer 
  runs 
  daily. 
  "We 
  made 
  two 
  

   excursions 
  of 
  three 
  days 
  each 
  to 
  this 
  island. 
  The 
  shores 
  are 
  

   mostly 
  steep, 
  but 
  sand 
  beaches, 
  ledges, 
  and 
  enormous 
  frag- 
  

   ments 
  of 
  rocks, 
  afford 
  many 
  favorable 
  stations 
  for 
  the 
  Mol- 
  

   lusks. 
  At 
  high 
  water, 
  a 
  small 
  island, 
  on 
  the 
  northeast 
  side, 
  

   is 
  cut 
  off 
  from 
  the 
  principal 
  island, 
  but 
  at 
  low 
  water 
  a 
  high 
  

   ridge 
  of 
  sand 
  unites 
  them. 
  Here 
  the 
  elegant 
  Conus 
  Maho- 
  

   gani, 
  Strombus 
  Peruvianus, 
  Natica 
  otis, 
  Corbulaovulata, 
  &c., 
  

   were 
  found. 
  

  

  These 
  varieties 
  of 
  station 
  enabled 
  us 
  to 
  find 
  a 
  multitude 
  

   of 
  species 
  in 
  their 
  proper 
  haunts. 
  But 
  in 
  addition 
  to 
  this 
  ad- 
  

   vantage, 
  the 
  hermit 
  crabs 
  {Paguridae) 
  swarmed 
  here, 
  as 
  

   elsewhere 
  in 
  tropical 
  regions. 
  Some 
  of 
  the 
  smaller 
  species 
  

   have 
  the 
  habit 
  of 
  congregating 
  in 
  heaps 
  of 
  many 
  hundreds 
  

  

  * 
  Tliis 
  name 
  is 
  sometimes 
  ■written, 
  erroneously 
  we 
  believe, 
  Tabago 
  ; 
  arvd 
  

   Bometimes, 
  in 
  the 
  publications 
  of 
  the 
  London 
  Conchologists, 
  Saboga. 
  

  

  