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  Panama 
  Shells. 
  intrcduction. 
  

  

  neath, 
  accommodate 
  a 
  great 
  diversity 
  of 
  species 
  : 
  in 
  some 
  

   parts, 
  flats 
  of 
  mud 
  or 
  of 
  sand 
  prevail. 
  

  

  On 
  the 
  west 
  of 
  the 
  city 
  is 
  a 
  very 
  broad 
  gently 
  sloping 
  

   beach 
  of 
  fine 
  sand, 
  where 
  Oliva, 
  Tellina, 
  Donax, 
  and 
  Artemis 
  

   abound. 
  Then 
  proceeding 
  westward 
  we 
  find 
  alternating 
  

   ledges 
  of 
  trachytic 
  and 
  basaltic 
  rocks, 
  sand 
  beaches, 
  and 
  

   broad 
  muddy 
  or 
  sandy 
  flats, 
  with 
  groves 
  of 
  trees 
  a 
  little 
  above 
  

   half 
  tide 
  level. 
  Here 
  during 
  the 
  recess 
  of 
  the 
  tide, 
  the 
  col- 
  

   lector 
  finds 
  an 
  agreeable 
  shade, 
  and 
  gathers 
  Purpurae 
  and 
  

   huge 
  Littorinae 
  from 
  the 
  trees, 
  and 
  numerous 
  species 
  of 
  Ve- 
  

   neridae, 
  of 
  Columbella, 
  the 
  little 
  and 
  elegant 
  Veritina 
  picta, 
  

   and 
  sometimes 
  the 
  massive 
  Area 
  grandis, 
  among 
  the 
  sticks 
  

   and 
  moss-like 
  Algae 
  beneath. 
  Three 
  miles 
  west 
  of 
  Panama 
  

   a 
  Rio 
  Grande 
  enters 
  the 
  bay, 
  and 
  is 
  bordered 
  by 
  impenetra- 
  

   ble 
  thickets 
  of 
  mangroves 
  and 
  not 
  impenetrable 
  ooze. 
  

  

  On 
  the 
  east 
  side 
  of 
  Panama 
  is 
  a 
  steep 
  sand 
  beach, 
  at 
  the 
  

   bottom 
  of 
  which 
  the 
  flats 
  consist 
  of 
  an 
  impalpable 
  mud 
  of 
  a 
  

   creamy 
  consistence. 
  On 
  this 
  fluid, 
  Marginella 
  sapotilla 
  crawls 
  

   or 
  rather 
  glides 
  rapidly 
  about. 
  Between 
  two 
  and 
  three 
  miles 
  

   to 
  the 
  East, 
  there 
  are 
  ledges 
  of 
  smooth 
  basaltic 
  rocks, 
  with 
  

   abundant 
  Littorinae, 
  Fissurellae, 
  and 
  Siphonariae. 
  Here 
  too 
  

   are 
  marine 
  groves, 
  rising 
  from 
  a 
  stony 
  surface, 
  by 
  the 
  side 
  of 
  

   which 
  a 
  small 
  rivulet 
  comes 
  in. 
  At 
  high 
  water 
  mark 
  is 
  a 
  man- 
  

   grove 
  thicket, 
  beneath 
  which 
  in 
  near 
  proximity 
  we 
  find 
  the 
  

   Potamides, 
  Arcse, 
  a 
  large 
  Cyrena, 
  Potamomyse, 
  and 
  the 
  ele- 
  

   gant 
  Auricula 
  concinna, 
  and 
  over 
  head 
  is 
  Littorina 
  pulchra, 
  

   but 
  almost 
  as 
  rare 
  as 
  beautiful. 
  A 
  little 
  farther 
  up. 
  where 
  the 
  

   water 
  is 
  nearly 
  fresh, 
  occurs 
  the 
  Neritina 
  Guayaquilensis, 
  

   whose 
  thin 
  depressed 
  elliptical 
  shell 
  attests 
  its 
  fluviatile 
  ha- 
  

   bits, 
  unlike 
  the 
  solid 
  ellipsoidal 
  shell 
  of 
  the 
  marine 
  N. 
  picta. 
  

  

  This 
  diversity 
  of 
  station 
  was 
  multiplied 
  by 
  the 
  high 
  tides. 
  

   In 
  the 
  office 
  of 
  the 
  Pacific 
  Mail 
  Steamship 
  Co., 
  wo 
  saw 
  it 
  

   recorded 
  on 
  a 
  tide 
  table, 
  that 
  the 
  extreme 
  difference 
  of 
  high 
  

   and 
  low 
  water 
  had 
  amounted 
  to 
  28 
  feet. 
  The 
  ordinary 
  tides 
  

  

  