﻿BLOOMER 
  & 
  OVEllTON 
  : 
  ON 
  ANODONTA 
  AND 
  PSEUDANODOXTA. 
  203 
  

  

  usually 
  of 
  an 
  orange 
  shade, 
  becoming 
  more 
  pronounced 
  towards 
  the 
  

   keel. 
  The 
  mantle 
  is 
  generally 
  of 
  an 
  orange 
  shade, 
  varying 
  in 
  

   intensity 
  and 
  occasionally 
  spreading 
  to 
  the 
  dorsal 
  surface 
  as 
  well 
  as 
  

   colouring 
  the 
  labial 
  palps 
  and 
  adductor 
  muscles. 
  

  

  The 
  mantle 
  is 
  thin 
  and 
  bordered 
  by 
  the 
  circurapallial 
  muscles 
  

   which 
  form 
  a 
  shallow 
  band 
  (Fig. 
  1, 
  CM.). 
  At 
  the 
  posterior 
  end 
  

   the 
  mantle 
  encloses 
  the 
  siphonal 
  apertures, 
  the 
  inhalent 
  {In. 
  A.) 
  

   being 
  larger 
  than 
  the 
  exhalent 
  one 
  [E.v.A.). 
  The 
  mantle 
  fringe 
  of 
  

   the 
  former 
  has 
  from 
  fifty 
  to 
  seventy 
  tentacles 
  on 
  each 
  side. 
  

  

  On 
  the 
  removal 
  of 
  the 
  shell 
  the 
  exposed 
  terminal 
  or 
  lateral 
  parts 
  

   of 
  the 
  pallial 
  and 
  pedal 
  muscles 
  present 
  the 
  following 
  characters 
  : 
  — 
  

  

  The 
  anterior 
  adductor 
  {A. 
  A.) 
  is 
  curved 
  anteriorly, 
  flattened 
  

   posteriorlj-, 
  and 
  has 
  the 
  ventral 
  larger 
  than 
  the 
  dorsal 
  part. 
  

  

  The 
  posterior 
  adductor 
  (P. 
  A.) 
  is 
  posteriorly 
  deeply 
  and 
  broadly 
  

   convex 
  ; 
  anteriorly 
  it 
  is 
  slightly 
  concave. 
  

  

  The 
  anterior 
  retractor 
  pedis 
  {R.P.A.) 
  is 
  irregularly 
  shaped, 
  with 
  

   the 
  ventro-anterior 
  edge 
  resting 
  on 
  the 
  centre 
  of 
  the 
  posterior 
  side 
  of 
  

   the 
  anterior 
  adductor. 
  

  

  The 
  anterior 
  protractor 
  pedis 
  {P.P. 
  A.) 
  is 
  round, 
  and 
  situated 
  some 
  

   distance 
  from 
  the 
  ventro-posterior 
  edge 
  of 
  the 
  anterior 
  adductor. 
  

  

  The 
  posterior 
  retractor 
  pedis 
  {P. 
  P.P.) 
  is 
  of 
  an 
  oblong 
  sliape 
  and 
  

   has 
  its 
  posterior 
  edge 
  in 
  contact 
  with 
  the 
  dorsal 
  side 
  of 
  the 
  posterior 
  

   adductor. 
  

  

  A. 
  certain 
  latitude 
  must 
  be 
  allowed 
  in 
  the 
  description 
  of 
  the 
  shape 
  

   of 
  the 
  muscles 
  as 
  they 
  all, 
  more 
  or 
  less, 
  vary, 
  and 
  tliis 
  particularly 
  

   applies 
  to 
  the 
  protractor 
  and 
  retractor 
  muscles. 
  In 
  these 
  the 
  chief 
  

   point 
  to 
  be 
  remembered 
  is 
  their 
  relative 
  position 
  to 
  the 
  adductor 
  

   muscles. 
  

  

  Anodonta 
  anatina. 
  (Linn.). 
  

  

  Shell. 
  — 
  In 
  describing 
  this 
  species 
  Jeffreys 
  has 
  again 
  been 
  closely 
  

   followed. 
  

  

  Shell 
  oval, 
  ratlier 
  ventricose, 
  moderately 
  thick, 
  glossy, 
  olive 
  green 
  

   or 
  brown 
  with 
  darker 
  transverse 
  bands 
  denoting 
  the 
  lines 
  of 
  growth, 
  

   and 
  irregularly 
  wrinkled 
  in 
  the 
  same 
  direction 
  ; 
  periostracum 
  thick 
  ; 
  

   umbones 
  placed 
  at 
  a 
  distance 
  of 
  about 
  one-third 
  from 
  the 
  anterior 
  

   end 
  ; 
  ligament 
  comparatively 
  short 
  and 
  prominent 
  ; 
  dorsal 
  margin 
  or 
  

   liinge-line 
  ascending 
  for 
  some 
  distance 
  posteriorly 
  ; 
  anterior 
  side 
  

   rounded 
  and 
  gaping 
  ventrally, 
  with 
  an 
  oblique 
  slope 
  towards 
  the 
  

   ventral 
  edge 
  ; 
  posterior 
  side 
  compressed 
  above, 
  curved, 
  and 
  abruptly 
  

   sloping 
  to 
  a 
  wedge-like 
  extremity; 
  ventral 
  margin 
  curved; 
  hinge 
  

   and 
  ridge-like 
  plate 
  the 
  same 
  as 
  in 
  A. 
  cygncea; 
  inside 
  the 
  shell 
  is 
  

   thick, 
  pearly 
  white 
  and 
  iridescent, 
  while 
  the 
  muscular 
  and 
  pallial 
  

   impressions 
  are 
  deep 
  and 
  quite 
  distinct. 
  

  

  Animal. 
  — 
  The 
  specimen 
  described 
  (PL 
  XI, 
  Fig. 
  2) 
  was 
  taken 
  from 
  

   Longmore 
  Pool, 
  Sutton 
  Coldfield. 
  

  

  The 
  dorsal 
  edge 
  is 
  curved, 
  but 
  it 
  ascends 
  from 
  the 
  umbonal 
  region 
  

   for 
  some 
  distance 
  towards 
  the 
  posterior 
  end. 
  The 
  anterior 
  edge 
  is 
  

   curved, 
  whilst 
  the 
  posterior 
  is 
  very 
  bluntly 
  triangular 
  with 
  its 
  apical 
  

  

  VOL. 
  XII.— 
  AUGUST, 
  1917. 
  15 
  

  

  