﻿AND 
  OTHER 
  FAMILIES. 
  35 
  

  

  Unio 
  Haysianus. 
  Plate 
  III. 
  fig. 
  7. 
  

  

  Testa 
  subrotundd, 
  subventricosd, 
  ad 
  baseos 
  marginem 
  posteriorem 
  deniatd 
  ; 
  

   valvulis 
  subcrassis 
  ; 
  natibus 
  prominent 
  ibus 
  ; 
  epidermide 
  luteo-fuscd 
  Isevissimaqtie 
  ; 
  

   radiis 
  obsohtis 
  ; 
  dentibus 
  cardinalibus 
  in 
  lobos 
  divisis, 
  lateralibus 
  crassis 
  rectisque 
  ; 
  

   margaritd 
  cacao 
  colore 
  tinctd. 
  

  

  Shell 
  subrotund, 
  slightly 
  ventricose, 
  dentate 
  at 
  posterior 
  basal 
  margin 
  ; 
  valves 
  scarcely- 
  

   thick 
  ; 
  beaks 
  elevated 
  ; 
  epidermis 
  yellowish 
  brown 
  and 
  very 
  smooth 
  ; 
  rays 
  obsolete 
  ; 
  

   cardinal 
  teeth 
  lobed 
  ; 
  lateral 
  teeth 
  thick 
  and 
  straight; 
  nacre 
  chocolate 
  coloured. 
  

  

  Hab. 
  Cumberland 
  River. 
  Professor 
  Troost. 
  

  

  My 
  Cabinet. 
  

   Cabinet 
  of 
  Mr 
  Cooper. 
  

   Cabinet 
  of 
  Professor 
  Troost, 
  Nashville. 
  

   Diam. 
  -6, 
  Length 
  -8, 
  Breadth 
  1 
  inch. 
  

  

  Shell 
  subrotund, 
  nearly 
  equilateral, 
  slightly 
  ventricose, 
  dentate 
  at 
  

   posterior 
  margin, 
  depressed 
  before 
  the 
  umbonial 
  slope 
  ; 
  substance 
  of 
  the 
  

   shell 
  scarcely 
  thick 
  ; 
  beaks 
  thick 
  and 
  elevated 
  ; 
  epidermis 
  yellowish- 
  

   brown, 
  very 
  smooth 
  and 
  shining 
  ; 
  rays 
  obsolete 
  ; 
  cardinal 
  teeth 
  lobed, 
  

   double 
  in 
  the 
  left 
  valve, 
  single 
  and 
  rising 
  from 
  a 
  pit 
  in 
  the 
  right 
  valve 
  ; 
  

   lateral 
  teeth 
  short, 
  thick 
  and 
  straight 
  ; 
  posterior 
  and 
  anterior 
  cicatrices 
  

   both 
  distinct 
  ; 
  dorsal 
  cicatrices 
  situated 
  within 
  the 
  cavity 
  of 
  the 
  shell 
  

   on 
  the 
  plate 
  between 
  the 
  cardinal 
  and 
  lateral 
  teeth 
  ; 
  cavity 
  of 
  the 
  beaks 
  

   deep 
  and 
  angulated 
  ; 
  nacre 
  chocolate 
  coloured 
  and 
  iridescent 
  posteriorly. 
  

  

  Remarks.— 
  -It 
  has 
  been 
  in 
  my 
  power 
  to 
  examine 
  only 
  four 
  or 
  five 
  

   specimens 
  of 
  this 
  exceedingly 
  interesting 
  shell. 
  In 
  each 
  of 
  these 
  there 
  

   is 
  more 
  or 
  less 
  of 
  a 
  dentate 
  appearance, 
  which 
  is 
  so 
  unusual 
  among 
  the 
  

   Naiades 
  that 
  it 
  may, 
  perhaps 
  with 
  propriety, 
  be 
  said 
  to 
  belong 
  to 
  some 
  

   American 
  species 
  only. 
  In 
  the 
  early 
  stages 
  of 
  growth 
  there 
  is 
  no 
  den- 
  

   tate 
  appearance. 
  The 
  U. 
  sulcatus 
  (nobis) 
  and 
  the 
  U. 
  arcseformis 
  

   (nobis), 
  are 
  frequently 
  furnished 
  with 
  this 
  curious 
  appendage. 
  The 
  

   dentate 
  variety, 
  mentioned 
  in 
  my 
  description 
  of 
  U. 
  sulcatus, 
  has 
  been, 
  

   by 
  Mr 
  Say, 
  erected 
  into 
  a 
  separate 
  species, 
  under 
  the 
  name 
  of 
  ridi- 
  

   hundus; 
  in 
  the 
  propriety 
  of 
  which, 
  however, 
  I 
  cannot 
  agree 
  with 
  that 
  

   naturalist. 
  In. 
  outline 
  the 
  present 
  species 
  resembles 
  the 
  U. 
  subrolun- 
  

  

  