﻿108 
  PROCEEDINGS 
  OF 
  THE 
  MALA.COLOGICAL 
  SOCIETY. 
  

  

  elongated 
  local 
  form 
  peculiar 
  to 
  England) 
  and 
  both 
  looked 
  upon 
  as 
  

   varieties 
  of 
  the 
  pearl 
  mussel. 
  This 
  conclusion 
  receives 
  further 
  

   support 
  from 
  the 
  fact 
  that 
  Lamarck 
  compares 
  the 
  shapes 
  of 
  the 
  

   two: 
  "EUe 
  [i.e. 
  TJ. 
  elongatus] 
  est, 
  proportionellement, 
  plus 
  etroite, 
  

   plus 
  allongee, 
  et 
  moins 
  sinueuse 
  que 
  la 
  precedente 
  [i.e. 
  U. 
  sinuatus']." 
  

   Deshayes, 
  who 
  edited 
  the 
  second 
  edition 
  of 
  Lamarck's 
  Histoire 
  

   naturelle 
  des 
  animaux 
  sans 
  vertebres, 
  and 
  had 
  access 
  to 
  his 
  collection, 
  

   recognized 
  the 
  true 
  affinity 
  of 
  W. 
  sinuatus 
  from 
  Lamarck's 
  type- 
  

   speciraen 
  and 
  omitted 
  from 
  the 
  text 
  the 
  erroneous 
  citations 
  referring 
  

   to 
  Margaritana 
  margaritifera. 
  The 
  retention 
  of 
  the 
  reference 
  to 
  

   Encyclopedic 
  methodique, 
  pi. 
  ccxlviii, 
  figs, 
  la, 
  h, 
  already 
  given 
  in 
  

   the 
  first 
  edition, 
  on 
  the 
  other 
  hand, 
  leaves, 
  as 
  first 
  pointed 
  out 
  by 
  

   Eossraassler, 
  one 
  illustration 
  — 
  certainly 
  not 
  conspicuous 
  for 
  its 
  

   excellence 
  — 
  of 
  U. 
  sinuatus. 
  

  

  In 
  spite 
  of 
  these 
  facts 
  doubt 
  has 
  been 
  expressed, 
  quite 
  recently, 
  as 
  

   to 
  the 
  correct 
  generic 
  position 
  of 
  our 
  species. 
  Simpson, 
  in 
  his 
  

   Synopsis, 
  already 
  cited, 
  p. 
  678, 
  considers 
  U. 
  sinuatus 
  a 
  form 
  of 
  

   £/". 
  crassus, 
  E,etz., 
  which, 
  curiously 
  enough, 
  he 
  refers 
  to 
  Margaritana. 
  

   With 
  regard 
  to 
  the 
  relation 
  of 
  U. 
  sinuatus 
  to 
  JI. 
  crassus 
  I 
  need 
  simply 
  

   mention 
  that, 
  apart 
  from 
  the 
  external 
  aspect 
  which 
  causes 
  the 
  latter 
  

   to 
  appear 
  as 
  a 
  miniature 
  representation 
  of 
  the 
  former, 
  the 
  two 
  species 
  

   have 
  nothing 
  in 
  common. 
  How 
  Simpson 
  can 
  regard 
  IT. 
  sinuatus 
  as 
  

   a 
  Margaritana 
  appears 
  to 
  me 
  totally 
  inexplicable, 
  especially 
  since 
  in 
  

   the 
  foot-note 
  to 
  his 
  Margaritana 
  crassa 
  he 
  mentions 
  the 
  presence 
  of 
  

   well-developed 
  laterals. 
  Moreover, 
  according 
  to 
  the 
  anatomy 
  of 
  the 
  

   soft 
  parts 
  of 
  a 
  specimen 
  from 
  Wandersleben 
  in 
  Thuringia 
  ^ 
  dissected 
  

   by 
  me, 
  it 
  is 
  a 
  true 
  Unio. 
  

  

  After 
  these 
  discursions 
  I 
  trust 
  Unio 
  sinuatus 
  will 
  be 
  left 
  in 
  peace 
  

   and 
  will 
  not 
  have 
  to 
  continue 
  further 
  perambulating 
  from 
  one 
  genus 
  

   to 
  another. 
  

  

  I 
  will 
  now 
  refer 
  very 
  shortly 
  to 
  the 
  other 
  Unios 
  living 
  in 
  the 
  

   Thames 
  Valley. 
  My 
  brother, 
  who 
  resides 
  in 
  England, 
  and 
  to 
  whom 
  

   I 
  am 
  indebted 
  for 
  nearly 
  all 
  my 
  English 
  Naiades, 
  collected 
  for 
  me 
  

   U. 
  pictorum, 
  L., 
  and 
  U. 
  tiimidtis, 
  Retz., 
  but 
  was 
  unable 
  to 
  find 
  a 
  single 
  

   specimen 
  of 
  U. 
  Batavus, 
  Lam. 
  This 
  absence 
  of 
  the 
  commonest 
  Unio 
  

   in 
  all 
  running 
  waters 
  on 
  the 
  European 
  Continent 
  is 
  confirmed 
  in 
  the 
  

   Census 
  of 
  the 
  British 
  Land 
  and 
  Freshwater 
  Mollusca, 
  but 
  is 
  in 
  direct 
  

   contradiction 
  to 
  the 
  statement 
  by 
  Maton 
  & 
  Rackett,^ 
  who 
  described 
  

   their 
  Mya 
  Batava 
  from 
  the 
  River 
  Kennet 
  in 
  Berkshire, 
  therefore 
  from 
  

   the 
  Thames 
  Valley. 
  On 
  the 
  other 
  hand, 
  the 
  remarks 
  of 
  these 
  two 
  

   English 
  authors, 
  whose 
  quick 
  eyes 
  did 
  not 
  fail 
  to 
  detect 
  dififerences 
  in 
  

   structure 
  of 
  the 
  hinges 
  of 
  other 
  mussels, 
  on 
  the 
  hinge 
  of 
  their 
  Mya 
  

   Batava 
  (" 
  cardo 
  ut 
  in 
  Mya 
  pictorum 
  ") 
  gives 
  the 
  impression 
  that 
  they 
  

  

  1 
  Retzius 
  (Diss. 
  Hist. 
  Nat., 
  1788, 
  p. 
  17) 
  cites 
  after 
  the 
  diagnosis 
  of 
  his 
  Unio 
  crassus, 
  

   Schrbter, 
  Flussconchylien, 
  1779, 
  pi. 
  ii, 
  fig. 
  2, 
  as 
  illustrating 
  his 
  species. 
  The 
  

   specimen 
  there 
  figured, 
  called 
  by 
  Schroter 
  Mi/a 
  testa 
  crassa, 
  originated 
  from 
  

   Wandersleben 
  in 
  Thuringia, 
  and 
  for 
  this 
  reason 
  I 
  attached 
  much 
  importance, 
  in 
  

   my 
  anatomical 
  investigations 
  of 
  the 
  European 
  Naiades, 
  to 
  the 
  fact 
  that 
  I 
  could 
  

   examine 
  specimens 
  of 
  U. 
  crassus 
  from 
  Schroter's 
  original 
  habitat. 
  

  

  - 
  Maton 
  & 
  Eackett, 
  Trans. 
  Linn. 
  Soc. 
  London, 
  1S07, 
  vol. 
  viii, 
  p. 
  37. 
  

  

  