﻿HAAS: 
  ON 
  XJNIONIDiE 
  IN 
  THE 
  THAMES 
  VALLEY, 
  111 
  

  

  genera. 
  I 
  think 
  the 
  characters 
  indicated 
  in 
  the 
  foregoing 
  comparative 
  

   tables 
  are 
  sufficient 
  to 
  demonstrate 
  the 
  claim 
  to 
  generic 
  rank 
  of 
  

   Pseudanodonta. 
  

  

  I 
  possess 
  a 
  specimen 
  of 
  Pseudanodonta 
  elongata, 
  Hoi., 
  from 
  the 
  

   Thames. 
  This 
  species 
  occurs 
  in 
  the 
  identical 
  form 
  in 
  the 
  Upper 
  

   Rhine, 
  the 
  Neckar, 
  the 
  Main, 
  the 
  Moselle, 
  the 
  Lower 
  Rhine, 
  and 
  

   the 
  Meuse, 
  and 
  is 
  probably 
  represented 
  also 
  in 
  the 
  Schelde 
  and 
  

   Seine. 
  It 
  differs 
  from 
  P. 
  complanala 
  from 
  the 
  Danube, 
  the 
  type 
  

   •of 
  the 
  gemis, 
  in 
  its 
  dwarf 
  elongated 
  form. 
  Other 
  species, 
  still 
  

   unnamed, 
  occur 
  in 
  the 
  Weser, 
  the 
  Elbe, 
  the 
  Oder, 
  and 
  in 
  Sweden. 
  

   Hanley 
  ^ 
  states 
  that 
  in 
  Linne's 
  collection 
  the 
  box 
  with 
  Anodonta 
  

   anatina 
  contains 
  a 
  Pseudanodonta 
  which 
  corresponds 
  exactly 
  with 
  the 
  

   iigure 
  in 
  Rossmassler, 
  Icon, 
  iv, 
  pi. 
  xx, 
  fig. 
  283. 
  The 
  figure 
  of 
  this 
  

   Linnean 
  Pseudanodonta^ 
  however, 
  represents 
  a 
  true 
  A. 
  anatina 
  in 
  its 
  

   ■elongated 
  state, 
  exactly 
  like 
  those 
  I 
  have 
  from 
  Sweden. 
  Misled 
  by 
  

   this 
  error 
  on 
  Hanley's 
  part, 
  Simpson 
  treats 
  Pseudanodonta 
  simply 
  as 
  

   Anodonta, 
  and 
  places 
  it 
  in 
  his 
  Synopsis 
  under 
  the 
  comprehensive 
  

   A. 
  eygnea. 
  

  

  In 
  conclusion, 
  and 
  in 
  order 
  to 
  complete 
  the 
  consideration 
  of 
  the 
  

   Unionidse 
  of 
  the 
  Thames, 
  I 
  must 
  refer 
  to 
  the 
  English 
  Anodontas. 
  In 
  

   this 
  connexion 
  a 
  question 
  crops 
  up 
  which 
  can 
  only 
  be 
  settled 
  by 
  the 
  

   examination 
  of 
  Linne's 
  collection 
  of 
  shells. 
  It 
  is 
  with 
  respect 
  to 
  

   the 
  nomenclature 
  of 
  the 
  species 
  of 
  Anodonta, 
  which 
  in 
  Germany, 
  

   through 
  Rossmassler's 
  influence, 
  is 
  treated 
  in 
  quite 
  a 
  different 
  way 
  

   from 
  that 
  in 
  England. 
  Hanley 
  certainly 
  states 
  that 
  Linne's 
  A. 
  cxjgnea 
  

   corresponds 
  with 
  the 
  figure 
  in 
  the 
  Iconographie, 
  pt. 
  iv, 
  pi. 
  xix, 
  

   fig. 
  280, 
  indicated 
  bj" 
  Rossmassler 
  as 
  A. 
  Cellensis, 
  Schrot. 
  Unfortunately 
  

   Hanley's 
  error 
  in 
  connexion 
  with 
  Fseudanodonta, 
  already 
  referred 
  to, 
  

   has 
  shaken 
  my 
  confidence 
  in 
  him 
  in 
  such 
  a 
  manner 
  that 
  I 
  will 
  not 
  at 
  

   present 
  attempt 
  to 
  settle 
  this 
  question 
  of 
  nomenclature, 
  but 
  must 
  

   defer 
  this 
  until 
  my 
  visit 
  to 
  London. 
  In 
  order, 
  however, 
  not 
  to 
  be 
  

   misunderstood 
  by 
  mj^ 
  English 
  readers 
  I 
  will 
  quote 
  with 
  each 
  specific 
  

   name 
  the 
  respective 
  figures 
  in 
  Rossmassler's 
  Iconographie. 
  In 
  

   (jermany 
  we 
  distinguish 
  only 
  two 
  species 
  of 
  Anodonta 
  — 
  A. 
  Cellensis, 
  

   Schrot. 
  (Icon., 
  pi. 
  xix, 
  fig. 
  280), 
  and 
  A. 
  piscinalis, 
  Miss. 
  (Icon., 
  

   pi. 
  xix, 
  fig. 
  281). 
  A. 
  anatina, 
  L. 
  (Icon., 
  pi. 
  xxix, 
  figs. 
  417-20), 
  is 
  

   ■considered 
  to 
  be 
  a 
  degenerate 
  form 
  of 
  A. 
  piscinalis, 
  as 
  found 
  in 
  brooks 
  

   with 
  a 
  strong 
  current. 
  A. 
  cycjnea 
  (Icon., 
  pi. 
  iii, 
  fig. 
  67) 
  is 
  a 
  convergent 
  

   form 
  between 
  A. 
  Cellensis 
  and 
  A. 
  piscinalis 
  found 
  in 
  pools 
  and 
  ponds 
  

   with 
  deep 
  tenacious 
  mud. 
  I 
  will 
  not 
  here 
  consider 
  the 
  other 
  forms 
  of 
  

   Anodonta, 
  and 
  only 
  refer 
  to 
  my 
  article 
  on 
  "Die 
  Najadenfauna 
  des 
  

   Oberrheins 
  vom 
  Diluvium 
  bis 
  zur 
  Jetzzeit 
  "." 
  

  

  I 
  Tpossess 
  A. 
  piscinalis, 
  Miss., 
  in 
  quite 
  typical 
  form 
  from 
  the 
  Thames 
  

   at 
  Surbiton. 
  This 
  species 
  is 
  also 
  conspicuous 
  — 
  as 
  far 
  as 
  the 
  specimens 
  

   from 
  this 
  locality 
  are 
  concerned 
  — 
  for 
  the 
  sharply 
  defined 
  nepionic 
  

   shell. 
  

  

  A. 
  Cellensis, 
  which 
  prefers 
  still 
  water, 
  will 
  hardly 
  be 
  found 
  in 
  the 
  

  

  ^ 
  Hanley, 
  Ipsa 
  Linnpei 
  Conchylia, 
  1858, 
  p. 
  144. 
  

   2 
  Abh. 
  Senckenb. 
  Naturf. 
  Ges., 
  1910. 
  

  

  