﻿202 
  

  

  ON 
  ANODONTA 
  CYGNJEA 
  (LINN.) 
  CONTRASTED 
  WITH 
  ANODONTA 
  

   AISIATINA 
  (LINN.); 
  AND 
  ON 
  PSEUDANODONTA 
  EOTHOMA- 
  

   GENSIS, 
  LOCAED. 
  

  

  Hy 
  H. 
  II. 
  Bloomku, 
  F.L.S., 
  and 
  H. 
  Ovekton. 
  

  

  Read 
  8th 
  December, 
  1916. 
  

  

  PLATE 
  XI. 
  

  

  TnE 
  questioned 
  relationsliip 
  of 
  Anodonta 
  anatina 
  to 
  A. 
  cygncea 
  is 
  tlie 
  

   reason 
  the 
  following 
  work 
  has 
  been 
  undertaken. 
  

  

  The 
  intention 
  in 
  the 
  first 
  instance 
  "was 
  to 
  make 
  a 
  more 
  exhaustive 
  

   investigation, 
  but 
  the 
  War 
  has 
  prevented 
  the 
  obtaining 
  of 
  specimens 
  

   from 
  a 
  number 
  of 
  important 
  places 
  in 
  this 
  country 
  as 
  well 
  as 
  from 
  

   the 
  Continent. 
  A 
  comparison 
  of 
  the 
  British 
  species 
  "with 
  the 
  

   Continental 
  forms 
  of 
  A7iodonta 
  would 
  have 
  conveyed 
  a 
  more 
  

   comprehensive 
  grasp 
  of 
  the 
  subject, 
  but 
  since 
  some 
  considerable 
  time 
  

   must 
  elapse 
  before 
  this 
  is 
  possible 
  it 
  is 
  felt 
  desirable 
  to 
  give 
  the 
  

   result 
  of 
  the 
  research 
  so 
  far, 
  incomplete 
  though 
  it 
  maybe. 
  

  

  It 
  is 
  further 
  hoped 
  that 
  the 
  ecological 
  portion 
  will 
  induce 
  other 
  

   conchologists 
  to 
  record 
  their 
  experiences 
  of 
  similar 
  areas. 
  

  

  Thanks 
  are 
  acknowledged 
  to 
  the 
  following 
  for 
  their 
  kindly 
  help 
  in 
  

   specimens 
  or 
  notes: 
  B. 
  B. 
  Woodward, 
  A. 
  S. 
  Kennard, 
  Dr. 
  F. 
  Haas, 
  

   J. 
  K. 
  B. 
  Masefield, 
  F. 
  Booth, 
  W. 
  Blake, 
  B. 
  11. 
  Lucas, 
  P. 
  T. 
  Deakin, 
  

   and 
  others. 
  

  

  Anodonta 
  cygn^a 
  (Linn.). 
  

  

  Shell. 
  — 
  In 
  the 
  following 
  description 
  Jeffreys 
  has, 
  to 
  a 
  great 
  extent, 
  

   been 
  followed. 
  

  

  Shell 
  oblong, 
  slightly 
  ventricose, 
  thin, 
  moderately 
  glossy, 
  3-ellowisli 
  

   green 
  or 
  brown, 
  transversely 
  and 
  irregularly 
  grooved 
  by 
  the 
  lines 
  of 
  

   growth, 
  and 
  wrinkled 
  in 
  the 
  same 
  direction 
  on 
  the 
  posterior 
  and 
  

   ventral 
  sides; 
  periostracum 
  thin; 
  umbones 
  placed 
  at 
  a 
  distance 
  of 
  

   nearly 
  one-fourth 
  from 
  the 
  anterior 
  extremity 
  ; 
  ligament 
  rather 
  long 
  

   and 
  strong, 
  partly 
  concealed 
  within 
  the 
  overlapping 
  edges 
  of 
  the 
  

   dorsal 
  margin 
  or 
  hinge-line, 
  which 
  is 
  straight; 
  anterior 
  side 
  not 
  

   gaping, 
  rounded, 
  and 
  somewhat 
  abruptly 
  sloping 
  veutrally 
  ; 
  posterior 
  

   side 
  gradually 
  sloping 
  and 
  compressed 
  above, 
  produced 
  into 
  a 
  rounded 
  

   wedge-like 
  extremity 
  and 
  slightly 
  gaping; 
  ventral 
  margin 
  slightly 
  

   curved; 
  inside 
  pearly 
  white 
  and 
  sometimes 
  iridescent 
  ; 
  hinge 
  slight, 
  

   having 
  a 
  rather 
  sharp 
  ridge-like 
  plate 
  on 
  the 
  posterior 
  side 
  in 
  each 
  

   valve 
  ; 
  muscular 
  and 
  pallial 
  scars 
  very 
  slight 
  and 
  often 
  indistinct. 
  

  

  Animal. 
  — 
  The 
  specimen 
  described 
  (PI. 
  XI, 
  Fig. 
  1) 
  was 
  taken 
  from 
  

   Bracebridge 
  Pool, 
  Sutton 
  Coldfield. 
  It 
  measures 
  100 
  mm. 
  antero- 
  

   posteriorly 
  by 
  55 
  mm. 
  dorso-ventrally, 
  is 
  somewhat 
  flattened 
  dorsally, 
  

   being 
  nearly 
  parallel 
  to 
  the 
  long 
  axis 
  of 
  the 
  animal, 
  is 
  curved 
  

   anteriorly, 
  slightlj' 
  curved 
  ventrally, 
  and 
  more 
  or 
  less 
  .bluntly 
  

   triangular 
  posteriorly. 
  

  

  The 
  colour 
  of 
  the 
  proximal 
  part 
  of 
  the 
  foot 
  is 
  white 
  or 
  greyish 
  

   white, 
  sometimes 
  tinged 
  with 
  orange, 
  whilst 
  the 
  distal 
  part 
  is 
  

  

  