﻿36 
  ON 
  THE 
  NAIADES, 
  

  

  dus; 
  it 
  is, 
  however, 
  more 
  oblique, 
  and 
  in 
  the 
  epidermis 
  more 
  shining. 
  

   It 
  is 
  not 
  so 
  oblique 
  as 
  the 
  sulcatus, 
  but 
  has 
  a 
  furrow 
  anterior 
  to 
  the 
  

   umbonial 
  slope 
  similar 
  to 
  that 
  species. 
  In 
  the 
  epidermis 
  it 
  differs 
  very 
  

   much, 
  the 
  sulcatus 
  being 
  finely 
  wrinkled 
  and 
  finely 
  rayed. 
  In 
  some 
  

   specimens 
  the 
  successive 
  rows 
  of 
  teeth 
  along 
  the 
  posterior 
  margin 
  cause 
  

   that 
  portion 
  of 
  the 
  shell 
  to 
  swell 
  out, 
  which 
  gives 
  it 
  a 
  rich 
  and 
  beauti- 
  

   ful 
  appearance. 
  It 
  is, 
  though 
  small, 
  among 
  the 
  most 
  interesting 
  of 
  

   our 
  species. 
  The 
  specimen 
  here 
  represented, 
  I 
  owe 
  to 
  the 
  kindness 
  of 
  

   Mr 
  Cooper. 
  It 
  is 
  with 
  pleasure 
  I 
  dedicate 
  this 
  species 
  to 
  my 
  friend, 
  

   Isaac 
  Hays, 
  M.D., 
  whose 
  talents 
  have 
  been 
  actively 
  and 
  successfully 
  

   engaged 
  many 
  years 
  in 
  the 
  promotion 
  of 
  natural 
  as 
  well 
  as 
  medical 
  

   science. 
  

  

  Unio 
  Hildrethianus. 
  Plate 
  III. 
  fig. 
  8. 
  

  

  Testa 
  angusto-ellipticd, 
  subcylindraccd, 
  valde 
  transversa, 
  insequilaterali 
  ; 
  valvu- 
  

   les 
  tenuibus 
  ; 
  dente 
  cardinali 
  in 
  valvuld 
  utrdque 
  unico, 
  later 
  ali 
  nulla 
  ; 
  margaritd 
  

   superne 
  fused, 
  inferne 
  albd 
  et 
  iridescente. 
  

  

  Shell 
  narrow-elliptical, 
  subcylindrical, 
  very 
  transverse, 
  inequilateral; 
  valves 
  thin; 
  

   cardinal 
  teeth 
  single 
  in 
  each 
  valve; 
  without 
  lateral 
  teeth; 
  nacre, 
  above 
  brown, 
  below 
  

   white 
  and 
  iridescent. 
  

  

  Hab. 
  Ohio, 
  near 
  Marietta. 
  Dr 
  Hildreth. 
  

  

  My 
  Cabinet. 
  

   Cabinet 
  of 
  Dr 
  Hildreth. 
  

   Cabinet 
  of 
  the 
  Academy 
  of 
  Natural 
  Sciences. 
  

   Diam 
  -5, 
  Length 
  -7, 
  Breadth 
  1-6 
  inches. 
  

  

  Shell 
  narrow-elliptical, 
  subcylindrical, 
  very 
  transverse, 
  inequilateral, 
  

   somewhat 
  compressed 
  at 
  basal 
  margin 
  ; 
  substance 
  of 
  the 
  shell 
  thin 
  be- 
  

   hind, 
  thicker 
  before 
  ; 
  beaks 
  slightly 
  elevated 
  ; 
  ligament 
  long 
  and 
  thin 
  ; 
  

   epidermis 
  dark 
  brown; 
  cardinal 
  teeth 
  lobed, 
  single 
  in 
  each 
  valve, 
  larger 
  

   and 
  wider 
  in 
  the 
  left 
  valve 
  ; 
  lateral 
  teeth 
  none 
  ; 
  anterior 
  and 
  posterior 
  

   cicatrices 
  both 
  confluent; 
  dorsal 
  cicatrices 
  in 
  the 
  centre 
  of 
  the 
  cavity 
  

   of 
  the 
  beaks; 
  cavity 
  of 
  the 
  beaks 
  shallow 
  and 
  tinged 
  with 
  dull 
  purple 
  ; 
  

   nacre 
  white 
  and 
  iridescent. 
  

  

  