﻿AND 
  OTHER 
  FAMILIES. 
  75 
  

  

  Symphynota 
  discoidea. 
  Plate 
  XI. 
  fig. 
  33. 
  

  

  Testa 
  subrhombed, 
  compressd, 
  transversa, 
  insequilaterali, 
  valvulis 
  tenuissimis, 
  

   postice 
  connatis 
  ; 
  natibus 
  paulum 
  undulatis, 
  compressis 
  ; 
  dentibus 
  in 
  valvuld 
  

   utrdque 
  lineam 
  simplicem 
  facientibus 
  ; 
  margaritd 
  alba 
  et 
  iridescente. 
  

  

  Shell 
  subrhomboidal, 
  compressed, 
  transverse, 
  inequilateral 
  ; 
  valves 
  very 
  thin, 
  con- 
  

   nate 
  behind 
  ; 
  beaks 
  slightly 
  undulated, 
  compressed 
  ; 
  teeth 
  in 
  both 
  valves 
  forming 
  a 
  

   simple 
  line 
  ; 
  nacre 
  white 
  and 
  iridescent. 
  

  

  Hab. 
  .... 
  * 
  G. 
  B. 
  Sowerby. 
  

  

  My 
  Cabinet. 
  

  

  Cabinet 
  of 
  Dr 
  Burrough. 
  

  

  Cabinet 
  of 
  W. 
  Hyde. 
  

  

  Diam. 
  1*2, 
  Length 
  2-4, 
  Breadth 
  3-9 
  inches. 
  

  

  Shell 
  subrhomboidal, 
  compressed, 
  transverse, 
  inequilateral, 
  finely 
  

  

  wrinkled 
  ; 
  substance 
  of 
  the 
  shell 
  very 
  thin 
  ; 
  posterior 
  slope 
  elevated 
  

  

  into 
  a 
  moderately 
  high 
  wing, 
  which 
  is 
  connate 
  ; 
  beaks 
  very 
  slightly 
  

  

  undulated, 
  compressed 
  ; 
  ligament 
  linear 
  ; 
  epidermis 
  dark 
  brown 
  ; 
  teeth 
  

  

  in 
  both 
  valves 
  forming 
  a 
  simple, 
  continuous, 
  fine 
  curve 
  line 
  ; 
  anterior 
  

  

  and 
  posterior 
  cicatrices 
  both 
  distinct; 
  dorsal 
  cicatrices 
  situated 
  in 
  the 
  

  

  centre 
  of 
  the 
  cavity 
  of 
  the 
  beaks 
  ; 
  cavity 
  of 
  the 
  beaks 
  almost 
  none 
  : 
  

  

  nacre 
  white 
  and 
  iridescent. 
  

  

  Remarks. 
  — 
  I 
  owe 
  to 
  the 
  kindness 
  of 
  G. 
  B. 
  Sowerby, 
  Esq. 
  the 
  spe- 
  

   cimen 
  here 
  described. 
  He 
  procured 
  it 
  of 
  " 
  a 
  dealer 
  from 
  Holland," 
  

   and 
  its 
  habitat 
  is 
  unknown. 
  It 
  has 
  the 
  characters 
  of 
  an 
  eastern 
  shell, 
  

   and 
  probably 
  came 
  from 
  Java. 
  In 
  the 
  outline 
  of 
  the 
  margin 
  it 
  resem- 
  

   bles 
  the 
  Symphynota 
  magnified 
  (described 
  in 
  this 
  memoir), 
  but 
  differs 
  

   from 
  it 
  in 
  being 
  compressed 
  and 
  in 
  the 
  possession 
  of 
  teeth. 
  In 
  the 
  

   teeth 
  it 
  has 
  a 
  stronger 
  resemblance 
  to 
  the 
  S. 
  hialata 
  (nobis) 
  than 
  to 
  

   any 
  other 
  species. 
  It 
  is, 
  however, 
  less 
  defined, 
  and 
  the 
  curve 
  is 
  less 
  

   regular, 
  the 
  posterior 
  portion 
  being 
  nearly 
  straight. 
  In 
  the 
  elevation 
  

   of 
  the 
  wing 
  it 
  differs 
  totally. 
  Our 
  present 
  shell 
  forms 
  an 
  interesting 
  

  

  * 
  Dr 
  Burrough 
  has 
  recently 
  obtained 
  it 
  in 
  the 
  rivers 
  of 
  China, 
  and 
  to 
  him 
  I 
  owe 
  the 
  fine 
  

   specimen 
  figured. 
  

  

  