﻿90 
  ON 
  THE 
  NAIADES, 
  

  

  After 
  examining 
  numerous 
  specimens 
  in 
  Europe 
  of 
  the 
  littoralis, 
  I 
  

   have 
  strong 
  doubts 
  if 
  the 
  shell 
  described 
  by 
  me 
  in 
  a 
  former 
  memoir, 
  

   under 
  the 
  name 
  of 
  incurvus, 
  be 
  not 
  a 
  peculiar 
  variety 
  of 
  it. 
  It 
  cer- 
  

   tainly 
  has 
  a 
  marked 
  similarity 
  to 
  a 
  fine 
  transverse 
  specimen 
  of 
  littoralis. 
  

   The 
  specimen 
  from 
  which 
  my 
  description 
  was 
  made, 
  was 
  sent 
  to 
  me 
  

   as 
  a 
  " 
  non 
  descript 
  from 
  Gibraltar," 
  by 
  Mrs 
  Mawe. 
  I 
  had 
  not 
  at 
  that 
  

   time 
  seen 
  very 
  fine 
  specimens 
  of 
  the 
  littoralis, 
  and 
  it 
  did 
  not 
  strike 
  me 
  

   that 
  there 
  was 
  a 
  similarity 
  to 
  such 
  as 
  I 
  had. 
  While 
  in 
  London, 
  that 
  

   excellent 
  conchologist, 
  Mr 
  G. 
  B. 
  Sowerby, 
  showed 
  me 
  a 
  specimen 
  

   precisely 
  similar 
  to 
  mine, 
  and 
  which 
  I 
  think 
  he 
  informed 
  me 
  was 
  from 
  

   the 
  collection 
  of 
  the 
  veteran 
  Humphreys. 
  In 
  one 
  valve 
  was 
  marked 
  

   in 
  ink 
  "Brazil;" 
  in 
  the 
  other 
  the 
  name 
  of 
  the 
  person 
  who 
  is 
  supposed 
  

   to 
  have 
  brought 
  it 
  from 
  that 
  country. 
  

  

  Unio 
  semirugata. 
  The 
  specimen 
  which 
  I 
  examined 
  in 
  the 
  Duke 
  

   de 
  Rivoli's 
  cabinet, 
  is 
  the 
  one 
  mentioned 
  as 
  being 
  in 
  Lamarck's 
  own 
  

   cabinet. 
  It 
  is 
  a 
  young 
  littoralis, 
  with 
  rather 
  more 
  undulations 
  than 
  

   usual. 
  

  

  Unio 
  nana. 
  I 
  saw 
  this 
  species 
  only 
  in 
  the 
  collection 
  of 
  Baron 
  de 
  

   Ferussac. 
  All 
  the 
  specimens 
  were 
  old 
  and 
  depauperated, 
  and 
  their 
  

   similarity 
  to 
  littoralis 
  so 
  great, 
  as 
  to 
  induce 
  me 
  to 
  believe 
  that 
  when 
  

   better 
  individuals 
  are 
  procured, 
  they 
  will 
  easily 
  be 
  referred 
  to 
  that 
  

   species. 
  

  

  Unio 
  delodonta. 
  The 
  specimen 
  cited, 
  and 
  which 
  I 
  examined 
  in 
  the 
  

   cabinet 
  of 
  the 
  Duke 
  de 
  Rivoli, 
  I 
  suspect 
  to 
  be 
  the 
  lacteolus 
  (nobis). 
  

   It 
  has 
  the 
  beaks 
  eroded, 
  and 
  therefore 
  does 
  not 
  present 
  the 
  peculiar 
  

   character 
  of 
  radiating 
  folds 
  at 
  the 
  point 
  of 
  the 
  beaks, 
  which 
  is 
  conse- 
  

   quently 
  omitted 
  in 
  Lamarck's 
  description. 
  

  

  Unio 
  sulcidens. 
  In 
  the 
  Duke 
  de 
  Rivoli's 
  collection 
  — 
  it 
  is 
  a 
  com- 
  

   pressed 
  eomplanatus 
  (Soland.), 
  from 
  the 
  Connecticut 
  River, 
  where 
  

   this 
  species 
  is 
  more 
  disposed 
  to 
  assume 
  that 
  character 
  than 
  in 
  any 
  

   river 
  in 
  the 
  United 
  States 
  with 
  which 
  I 
  am 
  acquainted. 
  

  

  Unio 
  rostrata. 
  This 
  is 
  one 
  of 
  the 
  numerous 
  species 
  made 
  from 
  the 
  

   pictorum 
  of 
  authors. 
  It 
  is 
  merely 
  an 
  elongated 
  variety 
  of 
  that 
  species 
  

   in 
  all 
  the 
  cabinets 
  where 
  I 
  have 
  seen 
  it 
  in 
  Europe, 
  

  

  Unio 
  Batava. 
  This 
  is 
  a 
  distinct 
  species 
  from 
  pictorum. 
  Baron 
  de 
  

   Ferussac 
  thinks 
  that 
  Maton 
  and 
  Racket 
  are 
  entitled 
  to 
  the 
  species. 
  

  

  