﻿80 
  ON 
  THE 
  NAIADES 
  

  

  Anodonta 
  Mortoniana. 
  Plate 
  XIII. 
  fig. 
  37. 
  

  

  Testd 
  subellipticd, 
  postice 
  sub-biangulata, 
  transversa, 
  valde 
  insequilaterali 
  ; 
  val- 
  

   vules 
  crassis 
  ; 
  epidermide 
  perfused 
  ; 
  clivo 
  umboniali 
  sulcato 
  ; 
  margaritd 
  argented 
  

   et 
  iridescenti. 
  

  

  Shell 
  subelliptical, 
  sub-biangular 
  behind, 
  transverse, 
  very 
  inequilateral 
  ; 
  valves 
  

   thick 
  ; 
  epidermis 
  intensely 
  brown 
  ; 
  umbonial 
  slope 
  furrowed 
  ; 
  nacre 
  silvery 
  and 
  iri- 
  

   descent. 
  

  

  Hab. 
  River 
  Parana, 
  South 
  America. 
  Dr 
  Burrough. 
  

   Cabinet 
  of 
  the 
  Academy 
  of 
  Natural 
  Sciences 
  of 
  Philadelphia. 
  

   Cabinet 
  of 
  Dr 
  Burrough. 
  

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

  

  Shell 
  subelliptical, 
  sub-biangulate 
  behind 
  ; 
  transverse, 
  very 
  inequi- 
  

   lateral, 
  somewhat 
  inflated, 
  furrowed 
  from 
  the 
  beak 
  to 
  the 
  posterior 
  

   margin 
  along 
  the 
  umbonial 
  slope; 
  substance 
  of 
  the 
  shell 
  thick; 
  beaks 
  

   retuse 
  and 
  scarcely 
  prominent; 
  ligament 
  long 
  and 
  narrow; 
  epidermis 
  

   intensely 
  brown 
  and 
  finely 
  wrinkled; 
  anterior 
  cicatrices 
  distinct; 
  pos- 
  

   terior 
  cicatrices 
  confluent; 
  dorsal 
  cicatrices 
  apparently 
  none; 
  cavity 
  of 
  

   the 
  beaks 
  subangular 
  and 
  shallow; 
  nacre 
  silvery 
  white 
  and 
  iridescent. 
  

  

  Remarks. 
  — 
  A 
  single 
  specimen 
  of 
  this 
  species, 
  which 
  is 
  distinct 
  from 
  

   any 
  described 
  Anodonta 
  I 
  have 
  seen, 
  was 
  sent 
  to 
  the 
  Academy 
  by 
  Dr 
  

   Burrough. 
  It 
  is 
  remarkably 
  thick, 
  silvery 
  and 
  iridescent, 
  and 
  has 
  an 
  

   exceedingly 
  dark 
  epidermis. 
  It 
  most 
  resembles, 
  perhaps, 
  the 
  elon- 
  

   gatus 
  of 
  Swainson. 
  It 
  is 
  less 
  transverse 
  than 
  that 
  shell, 
  rounded 
  only 
  

   anteriorly; 
  it 
  differs 
  in 
  not 
  having 
  "a 
  strong 
  flesh 
  coloured 
  tinge," 
  and 
  

   is 
  by 
  no 
  means 
  so 
  bright 
  a 
  brown 
  as 
  his 
  beautiful 
  figure. 
  

  

  Named 
  after 
  S. 
  G. 
  Morton, 
  M.D., 
  corresponding 
  secretary 
  of 
  the 
  

   Academy 
  of 
  Natural 
  Sciences 
  of 
  Philadelphia. 
  

  

  