﻿42 
  ON 
  THE 
  NAIADES, 
  

  

  Diam 
  2-4, 
  Length 
  2-5, 
  Breadth 
  3-5 
  inches. 
  

  

  Shell 
  very 
  globose, 
  inequilateral, 
  translucent, 
  very 
  smooth 
  and 
  

   bright 
  ; 
  connate 
  before 
  and 
  behind 
  the 
  beaks 
  ; 
  substance 
  of 
  the 
  shell 
  

   rather 
  thin 
  ; 
  beaks 
  very 
  round, 
  incurved 
  ; 
  epidermis 
  very 
  smooth, 
  and 
  

   pale 
  yellow 
  or 
  straw 
  colour; 
  umbones 
  very 
  round; 
  cardinal 
  teeth 
  

   very 
  lamellar, 
  elevated, 
  double 
  in 
  the 
  right 
  valve, 
  and 
  very 
  crenate 
  and 
  

   single 
  in 
  the 
  left 
  ; 
  the 
  line 
  of 
  the 
  lateral 
  and 
  cardinal 
  teeth 
  form 
  two 
  

   curves; 
  anterior 
  cicatrices 
  distinct; 
  posterior 
  cicatrices 
  confluent; 
  

   dorsal 
  cicatrices 
  situated 
  in 
  the 
  cavity 
  of 
  the 
  beaks 
  on 
  the 
  under 
  side 
  

   of 
  the 
  cardinal 
  teeth 
  ; 
  palleal 
  cicatrix 
  deeply 
  impressed 
  ; 
  cavity 
  of 
  

   the 
  beaks 
  very 
  round 
  and 
  very 
  deep 
  ; 
  nacre 
  thicker 
  near 
  the 
  margin, 
  

   beautifully 
  pearly 
  white 
  and 
  iridescent. 
  

  

  Remarks. 
  — 
  We 
  owe 
  to 
  Col. 
  Long 
  and 
  Mr 
  T. 
  Peale 
  the 
  knowledge 
  

   of 
  this 
  singular 
  and 
  distinct 
  species. 
  Without 
  a 
  tubercle 
  and 
  almost 
  

   rayless, 
  for 
  those 
  on 
  the 
  posterior 
  slope 
  are 
  obsolete, 
  it 
  is 
  among 
  the 
  

   most 
  beautiful 
  and 
  interesting 
  species 
  known. 
  The 
  Academy 
  is 
  in 
  

   possession 
  of 
  four 
  fine 
  specimens, 
  making 
  a 
  complete 
  suite 
  of 
  different 
  

   ages. 
  Three 
  of 
  them 
  are 
  perfect 
  enough 
  to 
  display 
  the 
  character 
  of 
  

   this 
  genus, 
  Symphynota, 
  notwithstanding 
  their 
  great 
  globosity. 
  It 
  

   is 
  more 
  capacious 
  than 
  any 
  of 
  the 
  Naiades 
  I 
  have 
  seen, 
  and 
  the 
  light 
  

   yellow 
  or 
  straw 
  coloured 
  epidermis 
  is 
  very 
  peculiar 
  — 
  in 
  form 
  it 
  most 
  

   resembles, 
  perhaps, 
  the 
  Unio 
  occidens 
  (nobis), 
  but 
  it 
  has 
  no 
  rays. 
  In 
  

   the 
  younger 
  individuals 
  there 
  is 
  a 
  transverse 
  rib-like 
  appearance 
  which 
  

   I 
  have 
  noticed 
  in 
  no 
  other 
  species 
  of 
  the 
  family. 
  

  

  Symphynota 
  Woodiana. 
  Plate 
  V. 
  fig. 
  13. 
  

  

  Testa 
  subpentagond, 
  postice 
  angiclatd, 
  super 
  umbones 
  turgidd, 
  insequilaterali, 
  

   transversa; 
  valvulis 
  teiitiibus 
  ; 
  epidermide 
  tenebroso-fuscd 
  et 
  obscuro-radiatd 
  ; 
  

   natibus 
  undulatis 
  ; 
  margaritd 
  alba 
  et 
  iridescente. 
  

  

  Shell 
  subpentagonal, 
  angular 
  behind, 
  turgid 
  over 
  the 
  umbones, 
  inequilateral, 
  trans- 
  

   verse 
  ; 
  valves 
  thin 
  ; 
  epidermis 
  dark 
  brown 
  and 
  obscurely 
  rayed 
  ; 
  beaks 
  undulated 
  ; 
  

   nacre 
  pearly 
  white 
  and 
  iridescent. 
  

  

  