﻿48 
  ON 
  THE 
  NAIADES, 
  

  

  spherical, 
  the 
  other 
  is 
  gibbous. 
  The 
  posterior 
  slope 
  of 
  the 
  young 
  

   specimen 
  is 
  decorated 
  with 
  six 
  distinct 
  green 
  rays, 
  there 
  being 
  three 
  

   on 
  each 
  valve. 
  

  

  Anodonta 
  palna. 
  Plate 
  VII. 
  fig. 
  18. 
  

  

  Testd 
  subovatd, 
  insequilaterali, 
  subcompressa 
  ; 
  valvulis 
  subcrassis 
  ; 
  epidermide 
  

   olivaced 
  et 
  obsolete 
  radiatd 
  ; 
  natibus 
  prorninentibus 
  ; 
  apicibus 
  granulatis 
  ; 
  cica- 
  

   tricibus 
  perspicuis 
  ; 
  mar 
  garitd 
  alba 
  ; 
  sed 
  in 
  natium 
  cavo 
  interdum 
  colore 
  salmo- 
  

   nis 
  tinctd. 
  

  

  Shell 
  subovate, 
  inequilateral, 
  rather 
  compressed 
  ; 
  valves 
  somewhat 
  thick; 
  epidermis 
  

   olive 
  with 
  obsolete 
  rays 
  ; 
  beaks 
  prominent 
  and 
  granulate 
  at 
  tip 
  ; 
  cicatrices 
  perceptible 
  ; 
  

   nacre 
  white, 
  sometimes 
  salmon 
  in 
  the 
  cavity 
  of 
  the 
  beaks. 
  

  

  Hab. 
  Bear 
  Grass 
  Creek, 
  near 
  Louisville. 
  Mr 
  T. 
  H. 
  Taylor. 
  

  

  My 
  Cabinet. 
  

  

  Cabinet 
  of 
  the 
  Academy 
  of 
  Natural 
  Sciences 
  of 
  Philadelphia. 
  

  

  Cabinet 
  of 
  Mr 
  Ronaldson. 
  

  

  Diam. 
  2-3, 
  Length 
  3-1, 
  Breadth 
  5-6 
  inches. 
  

  

  Shell 
  subovate, 
  inequilateral, 
  rather 
  compressed, 
  subangular 
  behind 
  ; 
  

  

  dorsal 
  line 
  slightly 
  curved; 
  substance 
  of 
  the 
  shell 
  thick; 
  epidermis 
  

  

  smooth, 
  olive 
  to 
  dark 
  green, 
  brighter 
  on 
  the 
  beaks; 
  rays 
  obsolete; 
  

  

  ligament 
  long 
  and 
  thick 
  ; 
  beaks 
  elevated, 
  granulate 
  at 
  tip 
  ; 
  cicatrices 
  

  

  perceptible 
  ; 
  cavity 
  of 
  the 
  beaks 
  rather 
  deep 
  and 
  rounded 
  ; 
  cavity 
  of 
  

  

  the 
  disk 
  somewhat 
  flattened 
  ; 
  nacre 
  white, 
  sometimes 
  salmon 
  coloured 
  

  

  in 
  and 
  about 
  the 
  cavity 
  of 
  the 
  beaks. 
  

  

  Remarks. 
  — 
  This 
  species 
  of 
  Anodonta 
  offers 
  quite 
  a 
  large 
  area 
  in 
  

   the 
  circumference 
  of 
  the 
  disk. 
  Some 
  specimens 
  are, 
  however, 
  more 
  

   transverse 
  than 
  the 
  one 
  here 
  described. 
  It 
  has 
  a 
  predisposition 
  to 
  

   salmon 
  colour 
  in 
  the 
  region 
  of 
  the 
  cavity 
  of 
  the 
  beaks, 
  and 
  this 
  is 
  

   sometimes 
  of 
  a 
  very 
  deep 
  tint. 
  The 
  colour 
  is 
  irregularly 
  distributed, 
  

   sometimes 
  quite 
  in 
  spots, 
  and 
  a 
  roughness, 
  apparently 
  a 
  disease, 
  often 
  

   accompanies 
  it 
  and 
  produces 
  a 
  carious 
  state 
  of 
  the 
  nacre. 
  It 
  perhaps 
  

   most 
  closely 
  resembles 
  the 
  A. 
  cataracta 
  (Say) 
  ; 
  but 
  is 
  usually 
  less 
  in- 
  

   flated, 
  is 
  thicker 
  in 
  the 
  substance 
  of 
  the 
  shell, 
  and 
  less 
  transverse. 
  

  

  