﻿HAAS: 
  ON 
  DMIOJflD^ 
  IN 
  THE 
  THAMES 
  VALLEY. 
  109 
  

  

  had 
  before 
  them 
  stunted, 
  abnormally 
  rounded 
  shells 
  of 
  W.pictonwi 
  ; 
  the 
  

   addition 
  of 
  the 
  term 
  rarissima 
  also 
  supports 
  this 
  view. 
  Mr. 
  Kennard, 
  

   whose 
  opinion 
  on 
  the 
  subject 
  I 
  solicited, 
  also 
  concludes 
  that 
  they 
  were 
  

   misled 
  by 
  an 
  erroneous 
  identification. 
  

  

  The 
  specimens 
  of 
  U. 
  picturum 
  and 
  U. 
  tumidus 
  collected 
  in 
  the 
  

   Thames 
  at 
  Surbiton 
  by 
  my 
  brother 
  are 
  characterized 
  by 
  sharply 
  

   defined 
  bronze 
  - 
  coloured 
  nepionic 
  shells, 
  which 
  show 
  the 
  apical 
  

   sculpture 
  peculiar 
  to 
  each. 
  

  

  From 
  the 
  Pleistocene 
  of 
  the 
  Thames 
  Valley 
  a 
  V. 
  littoralis 
  has 
  been 
  

   described, 
  as 
  also 
  from 
  the 
  Pleistocene 
  of 
  the 
  Khine 
  near 
  Mosbach. 
  On 
  

   careful 
  comparison 
  with 
  recent 
  specimens 
  of 
  U. 
  UUoralis 
  the 
  Mosbach 
  

   form 
  was 
  found 
  to 
  differ 
  from 
  the 
  former 
  in 
  the 
  structure 
  of 
  the 
  hinge, 
  

   which 
  led 
  me 
  to 
  describe 
  it 
  as 
  a 
  new 
  species 
  under 
  the 
  name 
  of 
  

   U. 
  Kinkelini} 
  Through 
  the 
  courtesy 
  of 
  Mr. 
  Kennard 
  I 
  received 
  

   from 
  Pleistocene 
  sand 
  of 
  three 
  different 
  ages 
  from 
  the 
  South 
  of 
  

   England 
  several 
  specimens 
  of 
  the 
  so-called 
  U. 
  littoralis 
  which 
  corre- 
  

   spond 
  with 
  the 
  Mosbach 
  form 
  in 
  a 
  peculiar 
  manner. 
  Whilst 
  the 
  shells 
  

   from 
  the 
  geologically 
  oldest 
  habitat, 
  Swanscomb, 
  were 
  almost 
  identical 
  

   with 
  my 
  U. 
  Kinlcelini, 
  those 
  from 
  Cray 
  ford 
  differed 
  somewhat 
  from 
  

   the 
  type, 
  and 
  the 
  geologically 
  most 
  recent 
  habitat, 
  Clacton, 
  produced 
  

   specimens 
  almost 
  identical 
  with 
  U. 
  liUoralis 
  from 
  the 
  !N^orth 
  of 
  France. 
  

   The 
  principal 
  character 
  of 
  TJ. 
  Kinkelini 
  I 
  considered 
  to 
  be 
  the 
  blunt 
  

   hinge, 
  which 
  was 
  further 
  distinguished 
  from 
  the 
  somewhat 
  neat 
  hinge 
  

   of 
  U. 
  littoralis 
  hj 
  the 
  possession 
  of 
  several 
  auxiliary 
  teeth. 
  The 
  

   English 
  forms 
  constitute 
  in 
  the 
  before-mentioned 
  sequence 
  a 
  complete 
  

   transition 
  from 
  typical 
  U. 
  Kinkelini 
  to 
  If. 
  littoralis, 
  so 
  that 
  the 
  

   Mosbach 
  form 
  is 
  not 
  so 
  isolated 
  as 
  I 
  concluded 
  at 
  first. 
  

  

  According 
  to 
  the 
  Census 
  of 
  the 
  British 
  Land 
  and 
  Freshwater 
  

   Mollusca 
  no 
  Margaritana 
  occurs 
  in 
  the 
  Thames 
  Valley. 
  In 
  view 
  of 
  

   the 
  abundance 
  of 
  lime 
  in 
  the 
  water 
  of 
  the 
  Thames 
  the 
  absence 
  of 
  this 
  

   genus 
  is 
  not 
  surprising, 
  since, 
  as 
  I 
  have 
  alreadj^ 
  mentioned, 
  Margari- 
  

   tana 
  only 
  occurs 
  in 
  water 
  deficient, 
  or 
  nearly 
  so, 
  in 
  lime. 
  As 
  a 
  proof 
  

   how 
  extraordinarily 
  sensitive 
  the 
  pearl 
  mussel 
  is 
  as 
  regards 
  water 
  rich 
  

   in 
  lime 
  the 
  following 
  experience 
  may 
  be 
  adduced. 
  During 
  nine 
  months 
  

   I 
  kept 
  alive 
  several 
  specimens 
  of 
  Margaritana 
  margaritifera 
  in 
  

   Heidelberg 
  Avater 
  destitute 
  of 
  lime, 
  which, 
  upon 
  being 
  placed 
  in 
  water 
  

   from 
  Frankfurt-a.-.M. 
  containing 
  comparatively 
  little 
  lime, 
  died 
  in 
  

   a 
  few 
  hours. 
  

  

  I 
  am 
  indebted 
  to 
  my 
  brother 
  for 
  the 
  discovery 
  of 
  a 
  mussel 
  which 
  

   appears 
  hitherto 
  to 
  have 
  been 
  overlooked 
  not 
  only 
  in 
  the 
  Thames 
  but 
  

   in 
  the 
  whole 
  of 
  England, 
  as 
  I 
  find 
  no 
  reference 
  to 
  its 
  occurrence 
  in 
  the 
  

   Census. 
  Although 
  represented 
  only 
  by 
  a 
  single, 
  but 
  unmistakable 
  

   specimen 
  from 
  the 
  Thames 
  at 
  Molesey, 
  I 
  have 
  before 
  me 
  the 
  species 
  

   of 
  Pseudanodonta, 
  Bour^'., 
  living 
  in 
  Germany 
  in 
  the 
  Rhine 
  district, 
  

   i.e. 
  P. 
  elongata, 
  Hoi. 
  Many 
  authors, 
  knowing 
  the 
  genus 
  Pseudanodonta 
  

   only 
  from 
  figures, 
  have 
  referred 
  its 
  various 
  forms 
  — 
  complanata, 
  Zglr., 
  

   elongata, 
  Hoi., 
  horealis, 
  Kob., 
  etc. 
  — 
  to 
  Anodonta, 
  since 
  these 
  two 
  genera 
  

   agree 
  in 
  the 
  absence 
  of 
  teeth 
  on 
  the 
  hinge 
  and 
  in 
  some 
  other 
  particulars. 
  

  

  1 
  Unio 
  Kinkelini, 
  Haas, 
  Nachr. 
  Blatt. 
  Deutsch. 
  Malak. 
  Ges., 
  1908, 
  p. 
  117. 
  

  

  