﻿78 
  ON 
  THE 
  NAIADES. 
  

  

  them, 
  the 
  epidermis 
  having 
  been 
  almost 
  completely 
  removed. 
  What 
  

   remains 
  indicates 
  it 
  to 
  be 
  greenish, 
  and 
  is 
  sufficient 
  to 
  warrant 
  its 
  being 
  

   represented 
  in 
  the 
  figure 
  with 
  a 
  perfect 
  epidermis 
  — 
  the 
  ligament 
  has 
  

   also 
  been 
  destroyed. 
  I 
  was 
  informed 
  by 
  the 
  dealer 
  that 
  it 
  came 
  from 
  

   Chili; 
  such 
  authority 
  cannot, 
  however, 
  be 
  entirely 
  relied 
  on. 
  The 
  

   cicatrices 
  of 
  this 
  interesting 
  species 
  are 
  very 
  remarkable, 
  particularly 
  

   that 
  of 
  the 
  mantle 
  near 
  the 
  margin 
  ; 
  the 
  palleal 
  impression 
  is 
  wide, 
  

   deeply 
  impressed, 
  and 
  in 
  the 
  posterior 
  part 
  of 
  the 
  shell 
  deflected 
  towards 
  

   the 
  centre 
  of 
  the 
  cavity, 
  somewhat 
  similar 
  to 
  the 
  excavation 
  of 
  the 
  

   palleal 
  cicatrix 
  of 
  the 
  genera 
  Galathea 
  and 
  Mactra. 
  The 
  character 
  of 
  

   this 
  cicatrix 
  is 
  different 
  from 
  that 
  of 
  any 
  species 
  of 
  the 
  family 
  Naiades 
  

   I 
  have 
  seen, 
  and 
  this 
  peculiarity 
  induces 
  me 
  to 
  believe 
  that 
  the 
  animal, 
  

   when 
  found, 
  may 
  prove 
  to 
  be 
  different 
  from 
  that 
  of 
  the 
  Anodonta. 
  

   Should 
  this 
  be 
  the 
  case, 
  it 
  will 
  belong 
  of 
  course 
  to 
  a 
  new 
  genus, 
  for 
  

   which 
  I 
  propose 
  the 
  name 
  of 
  Columba. 
  It 
  somewhat 
  resembles 
  the 
  

   An. 
  exotica 
  (Lam.). 
  It 
  is, 
  however, 
  narrower 
  before 
  and 
  broader 
  be- 
  

   hind 
  than 
  that 
  shell. 
  It 
  gapes 
  anteriorly 
  and 
  posteriorly 
  more 
  than 
  

   any 
  of 
  the 
  Naiades 
  with 
  which 
  I 
  am 
  acquainted. 
  It 
  is 
  perhaps 
  most 
  

   nearly 
  allied 
  to 
  the 
  Anodon 
  crassus 
  (Swainson), 
  but 
  differs 
  in 
  the 
  dor- 
  

   sal 
  line 
  being 
  straight, 
  the 
  nacre 
  being 
  pearly 
  salmon, 
  as 
  well 
  also 
  in 
  

   the 
  peculiar 
  character 
  of 
  the 
  palleal 
  cicatrix. 
  

  

  Anodonta 
  tenebricosa. 
  Plate 
  XII. 
  fig. 
  36. 
  

  

  Testa 
  ellipticd, 
  transversa 
  1 
  , 
  insequilaterd, 
  intus 
  margine 
  lata 
  et 
  corned; 
  sinii 
  

   incurvo 
  ; 
  valvulis 
  crassis 
  ; 
  epidermide 
  tenebroso 
  fused 
  ; 
  margaritd 
  alba 
  subcseruled 
  

   purpura 
  nubild, 
  iridescente. 
  

  

  Shell 
  elliptical, 
  transverse, 
  inequilateral, 
  interior 
  with 
  a 
  broad 
  horn 
  coloured 
  border; 
  

   sinus 
  incurved 
  ; 
  valves 
  thick; 
  epidermis 
  dark 
  brown 
  ; 
  nacre 
  pearly 
  white, 
  clouded 
  with 
  

   bluish 
  purple, 
  iridescent. 
  

  

  Hab. 
  River 
  Parana, 
  South 
  America. 
  Dr 
  Burrough. 
  

  

  My 
  Cabinet. 
  

  

  Cabinet 
  of 
  Dr 
  Burrough. 
  

  

  Cabinet 
  of 
  the. 
  Academy 
  of 
  Natural 
  Sciences 
  of 
  Philadelphia. 
  

  

  