﻿BLOOJIKR 
  & 
  OVEKTON 
  : 
  ON 
  ANODOXTA 
  AND 
  FSEUDANODONTA. 
  207 
  

  

  General 
  Conclusions. 
  — 
  Tho 
  examination 
  of 
  a 
  large 
  number 
  of 
  

   A. 
  cij(jnma 
  has 
  shown 
  tliat 
  the 
  siiells 
  are 
  fairly 
  constant 
  in 
  form 
  in 
  

   any 
  one 
  area, 
  whilst 
  they 
  have 
  been 
  found 
  to 
  present 
  certain 
  

   differences 
  when 
  contrasted 
  with 
  those 
  of 
  other 
  areas. 
  It 
  has 
  also 
  

   been 
  stated 
  that 
  there 
  is 
  a 
  degree 
  of 
  variation 
  in 
  the 
  external 
  

   characters 
  of 
  the 
  animals 
  themselves 
  as 
  far 
  as 
  the 
  muscular 
  parts 
  are 
  

   concerned 
  ; 
  there 
  may 
  further 
  be 
  a 
  slighter 
  variation 
  in 
  the 
  position 
  

   and 
  shape 
  of 
  the 
  siphonal 
  parts 
  and 
  the 
  number 
  of 
  tentacular 
  

   processes, 
  yet 
  a 
  critical 
  examination 
  bears 
  conviction 
  that 
  they 
  are 
  

   true 
  cygnma. 
  

  

  A. 
  anatina 
  shows 
  much 
  more 
  marked 
  variation, 
  although 
  the 
  type 
  

   shell 
  is 
  invariably 
  present 
  and 
  generally 
  in 
  considerable 
  numbers. 
  

   It 
  is 
  when 
  the 
  so-called 
  doubtful 
  specimens 
  are 
  scrutinized 
  that 
  the 
  

   difficulties 
  become 
  apparent, 
  and 
  it 
  is 
  really 
  astonishing 
  what 
  curious 
  

   shapes 
  the 
  shell 
  assumes 
  in 
  some 
  areas. 
  Out 
  of 
  one 
  pool 
  may 
  be 
  taken 
  

   very 
  many 
  specimens 
  all 
  differing 
  from 
  each 
  otlier 
  : 
  this, 
  it 
  must 
  be 
  

   admitted, 
  more 
  particularly 
  obtains 
  where 
  cygncea 
  and 
  anatina 
  are 
  

   found 
  in 
  the 
  same 
  water, 
  though 
  it 
  may 
  be 
  only 
  a 
  coincidence 
  and 
  

   arise 
  from 
  some 
  other 
  cause. 
  However, 
  an 
  examination 
  of 
  the 
  

   external 
  characters 
  of 
  the 
  animals 
  proves 
  them 
  to 
  be 
  variations 
  of 
  

   the 
  type 
  form 
  of 
  anatina, 
  because 
  of 
  the 
  predominance 
  of 
  the 
  

   characters 
  of 
  this 
  species. 
  It 
  is 
  not 
  to 
  be 
  presumed 
  that 
  hybridization 
  

   does 
  not 
  occur, 
  but 
  at 
  present 
  no 
  direct 
  evidence 
  is 
  available 
  of 
  it 
  

   taking 
  place. 
  

  

  The 
  conclusion 
  at 
  this 
  stage 
  points 
  to 
  the 
  fact 
  that 
  A. 
  cygnaa 
  and 
  

   A. 
  anatina 
  are 
  distinct 
  species, 
  that 
  liybridization 
  is 
  extremely 
  

   doubtful, 
  that 
  anatina 
  has 
  a 
  great 
  tendency 
  to 
  vary, 
  and 
  in 
  this 
  

   respect 
  it 
  would 
  seem 
  that 
  this 
  species 
  has 
  arrived 
  at 
  a 
  phase 
  known 
  

   to 
  occur 
  in 
  other 
  branches 
  of 
  Molliisca. 
  

  

  Ecological 
  Study 
  of 
  the 
  Anodons 
  of 
  Sutton 
  Park 
  Area. 
  

   The 
  bulk 
  of 
  the 
  material 
  used 
  in 
  this 
  investigation 
  has 
  been 
  

   obtained 
  from 
  the 
  vicinity 
  of 
  Sutton 
  ColdHeld 
  and 
  particularly 
  Sutton 
  

   Park. 
  The 
  latter, 
  a 
  large 
  enclosed 
  area, 
  retains 
  to 
  a 
  certain 
  extent 
  some 
  

   of 
  its 
  natural 
  features, 
  and 
  consists 
  of 
  heath 
  and 
  bog-land 
  interspersed 
  

   with 
  elevated 
  tracts 
  clothed 
  with 
  oaks, 
  hollies, 
  pines, 
  etc. 
  The 
  

   drainage 
  is 
  effected 
  by 
  two 
  small 
  streams 
  running 
  in 
  a 
  south-easterly 
  

   direction, 
  uniting 
  outside 
  the 
  park, 
  and 
  thence 
  flowing 
  into 
  the 
  

   Iliver 
  Tame. 
  From 
  the 
  beginning 
  of 
  the 
  fifteenth 
  to 
  the 
  end 
  of 
  the 
  

   eighteenth 
  century 
  these 
  streams 
  Avere 
  dammed 
  up 
  at 
  various 
  places 
  

   to 
  form 
  pools, 
  chiefly 
  for 
  industrial 
  purposes. 
  Some 
  have 
  since 
  been 
  

   filled 
  in, 
  but 
  six 
  situated 
  within 
  or 
  on 
  the 
  border 
  of 
  the 
  park 
  area 
  

   remain, 
  viz. 
  : 
  — 
  

  

  liracebridge 
  Pool, 
  made 
  1420. 
  

  

  BUickroot 
  Pool, 
  made 
  1757. 
  

  

  Keeper's 
  Pool, 
  made 
  between 
  1420 
  and 
  1462. 
  

  

  Longmore 
  Pool, 
  made 
  1735. 
  

  

  Powell's 
  Pool, 
  made 
  some 
  time 
  during 
  the 
  eighteenth 
  century. 
  

  

  Windl}'^ 
  Pool, 
  made 
  during 
  Norman 
  times. 
  

   The 
  accompanying 
  sketch 
  shows 
  their 
  respective 
  positions. 
  

  

  