﻿AND 
  OTHER 
  FAMILIES. 
  99 
  

  

  Poland, 
  Ohio. 
  It 
  is 
  very 
  nearly 
  allied 
  to 
  the 
  subrotundus 
  (nobis), 
  and 
  

   when 
  I 
  first 
  received 
  a 
  few 
  specimens, 
  I 
  doubted 
  if 
  it 
  was 
  more 
  than 
  

   a 
  variety 
  of 
  that 
  species. 
  Subsequently 
  receiving 
  from 
  the 
  same 
  natu- 
  

   ralist 
  more 
  and 
  better 
  specimens, 
  I 
  was 
  satisfied 
  that 
  it 
  was 
  specifically 
  

   different. 
  Specimens 
  of 
  the 
  true 
  subrotundus 
  having 
  accompanied 
  

   these, 
  it 
  could 
  not 
  be, 
  of 
  course, 
  a 
  variety 
  occasioned, 
  as 
  is 
  sometimes 
  

   the 
  case, 
  by 
  mere 
  locality. 
  It 
  differs 
  from 
  the 
  subrotundus 
  in 
  being 
  

   much 
  flatter, 
  in 
  having 
  smaller 
  beaks, 
  and 
  in 
  being 
  of 
  a 
  darker 
  brown 
  — 
  

   the 
  beaks 
  are 
  less 
  yellow 
  — 
  the 
  rays, 
  interrupted 
  like 
  that 
  shell, 
  tend 
  

   generally 
  nearer 
  to 
  the 
  margin. 
  In 
  older 
  specimens 
  than 
  the 
  one 
  

   figured, 
  the 
  posterior 
  part 
  becomes 
  protruded, 
  which 
  gives 
  an 
  oblique- 
  

   ness 
  to 
  the 
  shell. 
  

  

  Unio 
  Paranensis. 
  Plate 
  XIV. 
  fig. 
  42. 
  

  

  Testa 
  subrotundatd, 
  insequilaterali, 
  compressd 
  ; 
  valvulis 
  subcrassis 
  ; 
  natibus 
  

   plicatis 
  retusis 
  ; 
  dentibus 
  cardinalibus 
  recurvis, 
  in 
  valvuld 
  utrdque 
  diiplicibus 
  ; 
  

   lateralibus 
  sublongis 
  curvisque 
  ; 
  margaritd 
  albd 
  et 
  iridescente. 
  

  

  Shell 
  subrotund, 
  inequilateral, 
  compressed; 
  valves 
  somewhat 
  thick; 
  beaks 
  folded, 
  

   retuse 
  ; 
  cardinal 
  teeth 
  recurved, 
  double 
  in 
  both 
  valves 
  ; 
  lateral 
  teeth 
  rather 
  long 
  and 
  

   curved 
  ; 
  nacre 
  pearly 
  white 
  and 
  iridescent. 
  

  

  Hab. 
  River 
  Parana. 
  Dr 
  Burrongh. 
  

  

  Cabinet 
  of 
  Dr 
  Burrough. 
  

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

  

  Shell 
  subrotund, 
  disposed 
  to 
  be 
  pentagonal, 
  inequilateral, 
  compressed 
  

   towards 
  the 
  margin, 
  emarginate 
  on 
  the 
  posterior 
  dorsal 
  margin 
  ; 
  urn- 
  

   bonial 
  slope 
  flattened 
  ; 
  substance 
  of 
  the 
  shell 
  somewhat 
  thick 
  ; 
  beaks 
  

   rather 
  elevated, 
  longitudinally 
  folded, 
  retuse 
  ; 
  ligament 
  rather 
  long 
  and 
  

   thin 
  ; 
  epidermis 
  wrinkled, 
  shining, 
  greenish 
  on 
  the 
  beaks 
  and 
  brown 
  

   towards 
  the 
  margin, 
  furnished 
  with 
  very 
  obscure 
  curved 
  rays, 
  which 
  

   sweep 
  from 
  the 
  beak 
  towards 
  the 
  anterior 
  part 
  ; 
  cardinal 
  teeth 
  recurved, 
  

   compressed, 
  double 
  in 
  both 
  valves 
  ; 
  lateral 
  teeth 
  lamellar, 
  rather 
  long 
  

   and 
  curved 
  ; 
  anterior 
  cicatrices 
  confluent 
  ; 
  posterior 
  cicatrices 
  confluent 
  ; 
  

  

  