﻿i::/.GARA 
  FALLS 
  AND 
  VICINITY 
  247 
  

  

  lower 
  side 
  of 
  branches 
  and 
  floating 
  debris, 
  where 
  they 
  may 
  be 
  seen 
  

   moving 
  about 
  by 
  means 
  of 
  the 
  long, 
  flexible 
  foot. 
  

  

  Genus 
  pisiDiuM 
  Pfeifl'er. 
  1821 
  

  

  The 
  animal 
  closely 
  resembles 
  that 
  of 
  the 
  foregoing 
  genus, 
  but 
  the 
  

   siphons 
  are 
  united 
  to 
  the 
  end, 
  those 
  in 
  S 
  p 
  h 
  a 
  e 
  r 
  i 
  u 
  m 
  being 
  

   separated 
  and 
  more 
  elongated. 
  The 
  shell 
  is 
  trigonal 
  or 
  rounded 
  

   oval; 
  the 
  cardinal 
  teeth 
  are 
  very 
  small 
  and 
  double, 
  at 
  times 
  they 
  are 
  

   united 
  and 
  are 
  situated 
  directly 
  under 
  the 
  beaks; 
  the 
  lateral 
  teeth 
  

   are 
  elongated, 
  lamelliform, 
  double 
  in 
  the 
  right 
  valve, 
  single 
  in 
  the 
  

   left; 
  the 
  ligament 
  is 
  always 
  on 
  the 
  shorter 
  side. 
  

  

  Pisidium 
  virginicum 
  (Gmelin) 
  Bourg. 
  1853 
  (Fig. 
  179). 
  Tel- 
  

   lina 
  virginica 
  Gmelin 
  (1788. 
  ? 
  p. 
  3236, 
  pi. 
  

   159, 
  fig. 
  15). 
  Pisidium 
  v 
  i 
  r 
  g 
  i 
  n 
  i 
  c 
  u 
  m 
  Bourg. 
  

   (1853. 
  Am. 
  Malac. 
  1:53) 
  

  

  This 
  is 
  the 
  largest 
  Pisidium 
  found 
  in 
  this 
  region; 
  

   it 
  is 
  thick 
  and 
  oblique; 
  anterior 
  side 
  very 
  much 
  longer, 
  

  

  ^ 
  . 
  ? 
  Fig. 
  179 
  Pisidium 
  

  

  narrower 
  and 
  more 
  rounded 
  than 
  the 
  posterior 
  side, 
  ^irg'nicum. 
  xs 
  

   the 
  latter 
  being 
  much 
  broader 
  and 
  well 
  rounded; 
  beaks 
  prominent 
  

   and 
  posterior; 
  striae 
  coarse; 
  hinge 
  broad 
  and 
  with 
  two 
  large 
  cardinal 
  

   teeth; 
  laterals 
  small 
  and 
  delicate. 
  

   Locality. 
  Goat 
  island. 
  

  

  Pisidium 
  compressum 
  Prime 
  1851 
  (Fig. 
  180). 
  P. 
  

  

  com 
  press 
  um 
  Prime 
  (1851. 
  Bost. 
  soc. 
  nat. 
  hist. 
  

  

  Proc. 
  4:164) 
  

  

  Shell 
  solid, 
  triangular 
  and 
  somewhat 
  attenuated 
  at 
  

   the 
  beaks, 
  which 
  are 
  inflated; 
  anterior 
  side 
  longer, 
  

   Fig. 
  180 
  Pisidium 
  narrower 
  and 
  more 
  produced 
  than 
  the 
  posterior; 
  the 
  

  

  compressum. 
  x5 
  , 
  , 
  , 
  , 
  . 
  .^ 
  . 
  . 
  

  

  latter 
  subtruncate; 
  beaks 
  not 
  much 
  mtiated; 
  striae 
  

   distinct 
  and 
  regular; 
  hinge 
  thick, 
  having 
  strong, 
  short 
  teeth; 
  cardi- 
  

   nals 
  compressed; 
  laterals 
  placed 
  at 
  an 
  obtuse 
  angle 
  with 
  the 
  hinge. 
  

  

  Locality. 
  Goat 
  island. 
  

  

  Pisidium 
  abditum 
  Hald. 
  1841 
  (Fig. 
  181). 
  P. 
  abditum 
  

  

  Haldeman 
  (1841. 
  Acad. 
  nat. 
  sci. 
  Phil. 
  Proc. 
  1:53) 
  

  

  Shell 
  rounded, 
  oval 
  and 
  very 
  thin, 
  somewhat 
  elon- 
  

   gated, 
  beaks 
  small, 
  not 
  inflated 
  and 
  placed 
  posteriorly; 
  

   surface 
  smooth, 
  the 
  growth 
  lines 
  being 
  indistinct; 
  hinge 
  

   nearly 
  straight; 
  cardinal 
  teeth 
  small, 
  the 
  anterior 
  tooth 
  

   being 
  larger 
  and 
  more 
  prominent; 
  the 
  lateral 
  teeth 
  not 
  p,g 
  jgj 
  pjsidium 
  

   much 
  elongated. 
  abditum. 
  x2 
  

  

  Locality. 
  Goat 
  island. 
  

  

  