﻿32 
  ON 
  THE 
  NAIADES, 
  

  

  shell 
  thick 
  anteriorly 
  and 
  thin 
  posteriorly 
  ; 
  beaks 
  slightly 
  elevated 
  and 
  

   rounded 
  ; 
  ligament 
  short 
  and 
  thick 
  ; 
  epidermis 
  yellow, 
  with 
  numerous 
  

   small 
  green 
  rays 
  ; 
  cardinal 
  teeth 
  elevated, 
  double 
  and 
  crested 
  in 
  both 
  

   valves 
  ; 
  lateral 
  teeth 
  elevated 
  and 
  lamellar 
  ; 
  anterior 
  cicatrices 
  distinct 
  ; 
  

   posterior 
  cicatrices 
  confluent; 
  dorsal 
  cicatrices 
  situated 
  within 
  the 
  

   cavity 
  of 
  the 
  shell 
  on 
  the 
  plate 
  between 
  the 
  cardinal 
  and 
  lateral 
  teeth 
  

   and 
  on 
  the 
  base 
  of 
  the 
  cardinal 
  tooth 
  ; 
  cavity 
  of 
  the 
  beaks 
  wide 
  and 
  

   obtusely 
  angulate 
  ; 
  nacre 
  white 
  on 
  the 
  anterior 
  and 
  iridescent 
  on 
  the 
  

   posterior 
  portion. 
  

  

  Remarks. 
  — 
  While 
  engaged 
  in 
  my 
  last 
  memoir, 
  this 
  shell 
  attracted 
  

   my 
  attention. 
  I 
  had 
  not, 
  however, 
  then, 
  an 
  opportunity 
  of 
  examining 
  

   more 
  than 
  two 
  or 
  three 
  specimens, 
  and 
  finding 
  they 
  differed 
  much 
  in 
  

   some 
  characters, 
  I 
  deferred 
  noticing 
  them. 
  I 
  owe 
  to 
  Mr 
  Cooper 
  the 
  

   advantage 
  of 
  examining 
  his 
  specimens, 
  which 
  convinced 
  me 
  the 
  species 
  

   was 
  distinct. 
  This 
  is 
  one 
  of 
  those 
  species 
  which 
  sometimes 
  dilate 
  or 
  

   increase 
  about 
  the 
  region 
  of 
  the 
  umbonial 
  slope, 
  and 
  in 
  this 
  and 
  its 
  

   rays 
  it 
  resembles, 
  in 
  a 
  slight 
  degree, 
  the 
  U. 
  perplexus 
  (nobis). 
  The 
  

   enlargement 
  of 
  this 
  portion 
  of 
  the 
  shell, 
  which 
  is 
  generally 
  a 
  deep 
  

   green, 
  causes 
  it 
  to 
  have 
  a 
  different 
  outline, 
  being 
  there 
  more 
  rounded 
  

   and 
  causing 
  the 
  basal 
  margin 
  to 
  be 
  arcuate. 
  

  

  Unio 
  Ravenelianus. 
  Plate 
  III. 
  fig. 
  5. 
  

  

  Testa 
  late 
  ovatd, 
  obliqud, 
  indequilaterali, 
  post 
  ice 
  subanguhttd 
  ; 
  valvulis 
  anticc 
  

   crassioribus 
  ; 
  dentibus 
  cardinalibus 
  crassis 
  brevibusque 
  ; 
  luteralibus 
  crassis 
  rec- 
  

   tisque; 
  margaritd 
  albd 
  et 
  iridescente. 
  

  

  Shell 
  widely 
  ovate, 
  oblique, 
  inequilateral, 
  subangulate 
  posteriorly; 
  valves 
  thicker 
  

   anteriorly 
  ; 
  cardinal 
  teeth 
  short 
  and 
  thick; 
  lateral 
  teeth 
  straight 
  and 
  thick 
  ; 
  nacre 
  pearly 
  

   white 
  and 
  iridescent. 
  

  

  Hab. 
  French 
  Broad 
  River, 
  tributary 
  to 
  the 
  Tennessee, 
  near 
  Ashe- 
  

   ville, 
  N. 
  C. 
  Professor 
  Ravenel. 
  

  

  My 
  Cabinet. 
  

   Cabinet 
  of 
  the 
  Academy 
  of 
  Natural 
  Sciences 
  of 
  Philadelphia. 
  

  

  