﻿100 
  ON 
  THE 
  NAIADES, 
  

  

  dorsal 
  cicatrices 
  in 
  the 
  centre 
  of 
  the 
  cavity 
  of 
  the 
  beaks; 
  palleal 
  im- 
  

   pression 
  small 
  and 
  distant 
  from 
  the 
  margin 
  ; 
  cavity 
  of 
  the 
  shell 
  very 
  

   shallow 
  ; 
  cavity 
  of 
  the 
  beaks 
  small, 
  subangular 
  ; 
  nacre 
  pearly 
  white 
  and 
  

   iridescent. 
  

  

  Remarks. 
  — 
  I 
  am 
  indebted 
  to 
  the 
  kindness 
  of 
  Dr 
  Burrough. 
  for 
  the 
  

   advantage 
  of 
  examining 
  and 
  describing 
  this 
  interesting 
  species. 
  It 
  was 
  

   procured 
  by 
  him, 
  during 
  his 
  late 
  voyage 
  round 
  the 
  world, 
  at 
  Buenos 
  

   Ayres, 
  having 
  been 
  brought 
  from 
  the 
  river 
  Parana. 
  It 
  is 
  remarkable 
  

   for 
  its 
  outline, 
  its 
  expanded 
  basal 
  margin 
  and 
  folded 
  beaks. 
  

  

  Unio 
  Nashvillianus. 
  Plate 
  XIV. 
  fig. 
  43. 
  

  

  Testd 
  ellipticd, 
  transversa, 
  insequilaterali 
  ; 
  valvulis 
  subcrassis 
  ; 
  natibus 
  promi- 
  

   nulis 
  et 
  minute 
  undulatis 
  ; 
  dentibus 
  cardinalibus 
  laminatis 
  et 
  in 
  valvuld 
  utraque 
  

   duplicibus, 
  lateralibus 
  subrectis 
  ; 
  margaritd 
  alba. 
  

  

  Shell 
  elliptical, 
  transverse, 
  inequilateral 
  ; 
  valves 
  somewhat 
  thick 
  ; 
  beaks 
  slightly 
  ele- 
  

   vated 
  and 
  minutely 
  undulated 
  ; 
  cardinal 
  teeth 
  lamelliform 
  and 
  double 
  in 
  both 
  valves 
  ; 
  

   lateral 
  teeth 
  nearly 
  straight 
  ; 
  nacre 
  pearly 
  white. 
  

  

  Hab. 
  Cumberland 
  River. 
  Professor 
  Troost. 
  

   Ohio, 
  at 
  Louisville. 
  Dr 
  Fitch. 
  

   My 
  Cabinet. 
  

   Cabinet 
  of 
  Professor 
  Troost. 
  

   Diam. 
  -9, 
  Length 
  1-4, 
  Breadth 
  2-5 
  inches. 
  

  

  Shell 
  elliptical, 
  sometimes 
  truncate 
  behind, 
  transverse, 
  inequilateral; 
  

   substance 
  of 
  the 
  shell 
  somewhat 
  thick; 
  beaks 
  slightly 
  elevated 
  and 
  

   minutely 
  undulated 
  at 
  the 
  tip 
  ; 
  ligament 
  rather 
  short 
  and 
  straight 
  ; 
  

   epidermis 
  dark 
  brown, 
  obscurely 
  rayed 
  ; 
  cardinal 
  teeth 
  lamelliform, 
  

   disposed 
  to 
  be 
  crenulate, 
  double 
  in 
  both 
  valves 
  ; 
  lateral 
  teeth 
  nearly 
  

   straight, 
  the 
  inferior 
  section 
  in 
  the 
  left 
  valve 
  being 
  enlarged 
  towards 
  the 
  

   posterior 
  end 
  ; 
  anterior 
  cicatrices 
  distinct 
  ; 
  posterior 
  cicatrices 
  confluent 
  ; 
  

   dorsal 
  cicatrices 
  in 
  the 
  centre 
  of 
  the 
  cavity 
  of 
  the 
  beaks 
  ; 
  cavity 
  of 
  the 
  

   beaks 
  angular, 
  rather 
  shallow 
  ; 
  nacre 
  beautifully 
  pearly 
  white, 
  disposed 
  

   in 
  many 
  individuals 
  to 
  be 
  pinkish 
  on 
  the 
  posterior 
  part 
  of 
  the 
  shell. 
  

  

  