﻿46 
  ON 
  THE 
  NAIADES, 
  

  

  Anodonta 
  incerta. 
  Plate 
  VI. 
  fig. 
  16. 
  

  

  Testa 
  lato-ellipticd, 
  postice 
  subangulatd, 
  inflatd, 
  margine 
  dorsali 
  subrectd 
  ; 
  val- 
  

   vulis 
  tenuissimis 
  ; 
  epidermide 
  subviride, 
  obsolete 
  radiatd 
  ; 
  nallbus 
  complanatis 
  et 
  

   minute 
  undulatis; 
  cicatricibus 
  vix 
  cernendis; 
  margaritdcozruleo-albd 
  et 
  iridescente. 
  

  

  Shell 
  wide-elliptical, 
  subangular 
  behind, 
  inflated, 
  nearly 
  straight 
  on 
  the 
  dorsal 
  mar- 
  

   gin 
  ; 
  valves 
  very 
  thin 
  ; 
  epidermis 
  greenish 
  with 
  obsolete 
  rays, 
  beaks 
  flattened 
  and 
  

   minutely 
  undulated 
  ; 
  cicatrices 
  scarcely 
  perceptible 
  ; 
  nacre 
  bluish 
  white 
  and 
  iridescent. 
  

  

  Hab. 
  Ohio 
  River 
  near 
  Cincinnati. 
  T. 
  G. 
  Lea. 
  

  

  My 
  Cabinet. 
  

   Cabinet 
  of 
  the 
  Academy 
  of 
  Natural 
  Sciences 
  of 
  Philadelphia. 
  

   Cabinet 
  of 
  Professor 
  Vanuxem. 
  

   Cabinet 
  of 
  P. 
  H. 
  Nicklin. 
  

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

  

  Shell 
  wide-elliptical, 
  subangular 
  behind, 
  inequilateral, 
  inflated, 
  dor- 
  

   sal 
  margin 
  nearly 
  straight, 
  rounded 
  before 
  ; 
  substance 
  of 
  the 
  shell 
  very 
  

   thin; 
  epidermis 
  very 
  smooth, 
  green 
  and 
  olive 
  green 
  with 
  obsolete 
  

   rays, 
  three 
  being 
  more 
  distinct 
  on 
  the 
  posterior 
  part 
  of 
  each 
  valve 
  ; 
  lig- 
  

   ament 
  long 
  and 
  thin 
  ; 
  beaks 
  flattened, 
  minutely 
  undulated 
  near 
  the 
  

   tip 
  which 
  terminates 
  with 
  a 
  minute 
  point 
  from 
  which 
  an 
  indistinct 
  

   line 
  runs 
  towards 
  the 
  posterior 
  margin 
  ; 
  cicatrices 
  scarcely 
  perceptible 
  ; 
  

   cavity 
  of 
  the 
  beaks 
  scarcely 
  perceptible 
  ; 
  cavity 
  of 
  the 
  disk 
  deep 
  and 
  

   rounded 
  ; 
  nacre 
  bluish 
  white 
  and 
  iridescent. 
  

  

  Remarks. 
  — 
  Among 
  the 
  earliest 
  shells 
  I 
  procured 
  from 
  the 
  Ohio, 
  

   many 
  years 
  since, 
  were 
  several 
  specimens 
  of 
  this 
  fragile 
  Anodonta. 
  

   The 
  difficulty 
  of 
  separating 
  the 
  species 
  of 
  a 
  genus 
  with 
  so 
  few 
  tangible 
  

   characters 
  induced 
  me 
  to 
  lay 
  this 
  aside 
  with 
  some 
  other 
  species 
  until 
  

   more 
  leisure 
  w 
  r 
  ould 
  permit 
  a 
  thorough 
  examination. 
  It 
  perhaps 
  most 
  

   closely 
  resembles 
  the 
  Ji. 
  catarada 
  of 
  Say, 
  but 
  diners 
  from 
  it 
  peculiarly 
  

   in 
  the 
  flatness 
  of 
  the 
  beaks. 
  It 
  is 
  generally 
  more 
  inflated, 
  particu- 
  

   larly 
  near 
  the 
  umbonial 
  slope. 
  It 
  resembles 
  the 
  A. 
  Ferussaciana 
  (nobis), 
  

   the 
  description 
  of 
  which 
  see. 
  The 
  young 
  differ 
  from 
  the 
  old 
  in 
  being 
  

   much 
  compressed 
  and 
  in 
  having 
  rays 
  only 
  on 
  the 
  posterior 
  part 
  of 
  the 
  

   shell, 
  where 
  the 
  three 
  on 
  each 
  valve 
  are 
  distinctly 
  visible 
  — 
  they 
  are 
  

  

  