﻿BLOOMEK 
  & 
  OVERTON 
  : 
  ON 
  ANODONTA 
  AND 
  PSEVDANODONTA. 
  209 
  

  

  though 
  the 
  type 
  is 
  common, 
  there 
  is 
  a 
  very 
  large 
  number 
  of 
  specimens 
  

   which 
  vary 
  from 
  the 
  type. 
  There 
  is 
  also 
  a 
  number 
  of 
  specimens 
  

   wliich 
  at 
  first 
  were 
  considered 
  of 
  a 
  doubtful 
  nature. 
  Were 
  they 
  

   hybrids 
  or 
  extreme 
  variations 
  of 
  anatina 
  ? 
  As 
  previously 
  explained 
  

   they 
  proved 
  on 
  a 
  critical 
  examination 
  to 
  possess 
  such 
  characters 
  as 
  

   undoubtedly 
  determine 
  them 
  to 
  be 
  varieties 
  of 
  anatina, 
  and 
  as 
  such 
  

   they 
  are 
  accepted. 
  It 
  should 
  further 
  be 
  noted 
  that 
  this 
  tendency 
  to 
  

   vary 
  is 
  more 
  pronounced 
  in 
  this 
  pool 
  than 
  in 
  Longmore 
  Pool. 
  

  

  It 
  will 
  thus 
  be 
  observed 
  that 
  the 
  first 
  pool 
  on 
  each 
  stream 
  contains 
  

   only 
  one 
  species, 
  i.e. 
  A. 
  cygnoia 
  in 
  Bracebridge 
  Pool 
  and 
  A. 
  anatina 
  

   in 
  Longmore 
  Pool, 
  whilst 
  the 
  next 
  pool 
  in 
  succession 
  on 
  each 
  stream 
  

   contains 
  both. 
  It 
  is 
  only 
  when 
  A. 
  anatina 
  is 
  present 
  that 
  the 
  

   tendency 
  to 
  vary 
  prevails. 
  The 
  evidently 
  interesting 
  point 
  is 
  that 
  

   Bracebridge 
  Pool, 
  which 
  was 
  made 
  nearly 
  500 
  years 
  ago, 
  does 
  not 
  

   possess 
  A. 
  anatina 
  but 
  contains 
  A. 
  cygncea 
  in 
  large 
  numbers, 
  and 
  

   Longmore 
  Pool, 
  formed 
  180 
  years 
  ago, 
  does 
  not 
  contain 
  A. 
  cygncBa 
  

   but 
  has 
  anatina 
  in 
  profusion, 
  a 
  considerable 
  number 
  of 
  which 
  varies 
  

   from 
  tlie 
  type. 
  

  

  Since 
  the 
  above 
  was 
  written 
  a 
  few 
  dead 
  shells 
  of 
  A, 
  anatina 
  

   have 
  been 
  taken 
  near 
  the 
  upper 
  end 
  of 
  Bracebridge 
  Pool. 
  This 
  is 
  

   explained 
  by 
  the 
  fact 
  tliat 
  a 
  few 
  years 
  ago 
  a 
  local 
  naturalist 
  transferred 
  

   some 
  TJnio 
  pictorum 
  and^. 
  anatina 
  from 
  a 
  pool 
  which 
  was 
  beiug 
  filled 
  

   up 
  and 
  so 
  introduced 
  A. 
  anatina. 
  It 
  must 
  also 
  be 
  stated 
  that 
  a 
  few 
  

   dead 
  shells 
  of 
  A. 
  cygncea 
  have 
  been 
  likewise 
  taken 
  from 
  the 
  upper 
  

   end 
  of 
  Longmore 
  Pool, 
  and 
  there 
  ai'e 
  strong 
  grounds 
  for 
  believing 
  an 
  

   attempt 
  has 
  recently 
  been 
  made 
  to 
  introduce 
  this 
  species 
  into 
  this 
  pool 
  

   as 
  well. 
  

  

  PSEUDANODONTA 
  UOTHOMAGENSIS, 
  Locard. 
  

  

  Shell. 
  — 
  Shell 
  sub-oval, 
  slightly 
  compressed, 
  moderately 
  thick, 
  

   glossy, 
  dark 
  olive 
  or 
  brownish-green 
  colour, 
  transversely 
  grooved 
  by 
  

   lines 
  of 
  growth, 
  and 
  wrinkled 
  in 
  the 
  same 
  direction 
  on 
  the 
  anterior 
  

   and 
  posterior 
  sides 
  ; 
  epidermis 
  of 
  medium 
  thickness 
  ; 
  umbones 
  

   nodulous, 
  placed 
  at 
  a 
  distance 
  of 
  nearly 
  one-fourth 
  from 
  the 
  anterior 
  

   end 
  ; 
  ligament 
  long 
  and 
  prominent 
  ; 
  dorsal 
  side 
  from 
  umbonal 
  region 
  

   curved 
  anteriorly, 
  also 
  curved 
  and 
  ascending 
  posteriorly 
  ; 
  anterior 
  

   side 
  curved 
  and 
  sloping 
  ventrally, 
  widely 
  gaping, 
  slight 
  oblique 
  

   compression 
  posteriorly 
  inclined 
  as 
  from 
  the 
  umbonal 
  region 
  ; 
  

   posterior 
  side 
  compressed 
  above, 
  wedge 
  shaped 
  with 
  the 
  extremity 
  

   situated 
  somewhat 
  ventrally; 
  inside 
  pearly 
  white 
  with 
  the 
  central 
  

   part 
  tinged 
  a 
  salmon 
  cream 
  colour, 
  iridescent; 
  hinge 
  slight 
  with 
  

   a 
  prominent 
  ridge-like 
  plate 
  as 
  m 
  Anodonta 
  cygncea; 
  muscular 
  and 
  

   pallial 
  scars 
  distinct. 
  

  

  Animal. 
  — 
  The 
  specimen 
  described 
  was 
  taken 
  from 
  the 
  River 
  Teme^ 
  

   near 
  Knightswick, 
  by 
  Mr. 
  AY. 
  H. 
  Foxall, 
  to 
  whom 
  we 
  wish 
  to 
  express 
  

   our 
  thanks 
  for 
  this 
  and 
  other 
  specimens 
  he 
  has 
  allowed 
  us 
  to 
  

   examine. 
  

  

  The 
  animal 
  examined 
  measures 
  77 
  mm. 
  by 
  43 
  mm. 
  The 
  dorsal 
  

   portion 
  is 
  rouglily 
  triangular, 
  with 
  the 
  apex 
  about 
  10 
  mm. 
  nearer 
  the 
  

  

  