﻿bloomkr: 
  on 
  thk 
  anatomy 
  of 
  psammobia. 
  237 
  

  

  is 
  large 
  and 
  opens 
  on 
  tlie 
  ventral 
  side 
  into 
  the 
  csecnra 
  of 
  the 
  crystalline 
  

   style 
  (Fig. 
  9, 
  C.C.), 
  the 
  latter 
  being 
  long 
  and 
  curved 
  posteriorly. 
  

   As 
  in 
  the 
  other 
  species 
  the 
  intestine 
  (Fig. 
  10, 
  Li.) 
  appears 
  as 
  a 
  

   constricted 
  groove 
  on 
  the 
  right 
  side 
  of 
  the 
  caecum, 
  and 
  does 
  not 
  

   become 
  complete 
  xintil 
  it 
  leaves 
  the 
  distal 
  end 
  of 
  the 
  sac, 
  then 
  it 
  

   continues 
  in 
  a 
  sinuous 
  course 
  (Fig. 
  8, 
  In.) 
  to 
  the 
  posterior 
  part 
  of 
  the 
  

   stomach, 
  where 
  it 
  turns 
  and 
  passes 
  as 
  the 
  rectixm 
  (Fig. 
  8, 
  R.) 
  over 
  

   the 
  posterior 
  adductor 
  muscle. 
  

  

  Concerning 
  the 
  branchia 
  Dr. 
  Ridewood 
  says 
  : 
  " 
  The 
  plicse 
  of 
  the 
  

   outer 
  demibranch 
  have 
  about 
  14, 
  those 
  of 
  the 
  inner 
  about 
  18, 
  

   filaments 
  . 
  . 
  . 
  The 
  principal 
  filament 
  bears 
  a 
  false 
  resemblance 
  to 
  

   a 
  couple 
  of 
  ordinary 
  filaments, 
  due 
  to 
  the 
  sharply-cut 
  sides 
  of 
  the 
  

   frontal 
  groove, 
  and 
  to 
  the 
  fact 
  that 
  each 
  of 
  the 
  halves 
  is 
  about 
  the 
  

   same 
  size 
  as 
  an 
  ordinary 
  filament." 
  

  

  PsAMMOBiA 
  TELLiNELLA, 
  Lamarck. 
  

  

  External 
  Characters. 
  — 
  The 
  largest 
  animal 
  examined 
  measures 
  

   25 
  mm. 
  by 
  11 
  mm. 
  The 
  dorsal 
  surface 
  is 
  very 
  slightly 
  triangular, 
  

   but 
  the 
  remaining 
  ones 
  are 
  curved, 
  with 
  the 
  ventro-posterior 
  part 
  

   projecting 
  more 
  posteriorly, 
  the 
  same 
  as 
  in 
  the 
  other 
  species. 
  

  

  The 
  mantle-lobes 
  are 
  thin 
  and 
  possess 
  the 
  usual 
  marginal 
  muscular 
  

   band, 
  which, 
  like 
  that 
  in 
  P. 
  vespertina, 
  tapers 
  towards 
  the 
  rear 
  part 
  

   of 
  the 
  animal. 
  The 
  mantle-borders 
  have 
  the 
  three 
  characteristic 
  

   longitudinal 
  folds, 
  and 
  the 
  apposed 
  surfaces 
  of 
  the 
  middle 
  and 
  outer 
  

   ones 
  are 
  nowhere 
  fused 
  except 
  on 
  the 
  dorsal 
  sui'face 
  between 
  the 
  

   adductor 
  muscles, 
  but 
  the 
  inner 
  ones 
  coalesce 
  over 
  the 
  whole 
  of 
  the 
  

   dorsal 
  surface 
  of 
  the 
  posterior 
  adductor 
  and 
  the 
  greater 
  portion 
  of 
  

   the 
  anterior 
  adductor. 
  Between 
  the 
  anterior 
  adductor 
  and 
  the 
  

   musculus 
  cruciformis 
  is 
  the 
  large 
  pedal 
  aperture. 
  Above 
  the 
  latter 
  

   muscle 
  the 
  inner 
  folds 
  are 
  first 
  united, 
  then 
  they 
  are 
  connected 
  with 
  

   the 
  external 
  walls 
  of 
  the 
  proximal 
  portion 
  of 
  the 
  siphon 
  as 
  in 
  

   P. 
  vei^pertina. 
  The 
  middle 
  fold 
  carries 
  a 
  tentacular 
  fringe, 
  and 
  the 
  

   pallium 
  extends 
  some 
  distance 
  posteriorly 
  to 
  the 
  divergent 
  inner 
  

   fold, 
  and 
  is 
  capable 
  of 
  quite 
  enclosing 
  the 
  withdrawn 
  siphonal 
  tubes. 
  

  

  Comparatively 
  the 
  siphonal 
  tubes 
  (Fig, 
  11, 
  In.S. 
  and 
  Jix.S.) 
  do 
  

   not 
  appear 
  to 
  be 
  so 
  large 
  or 
  muscular 
  as 
  those 
  of 
  P. 
  vespertina, 
  and 
  

   the 
  proximal 
  part 
  of 
  the 
  siphon 
  is 
  not 
  situated 
  so 
  far 
  anteriorlj-. 
  

   The 
  foot 
  is 
  large 
  and 
  muscular, 
  and 
  usually 
  lies 
  in 
  an 
  anterior 
  

   direction. 
  

  

  The 
  anterior 
  adductor 
  muscle 
  (Fig. 
  11, 
  A. 
  A.), 
  situated 
  on 
  the 
  

   antero-dorsal 
  side, 
  lies 
  parallel 
  to 
  the 
  edge 
  of 
  the 
  mantle 
  with 
  its 
  

   ends 
  conforming 
  to 
  the 
  convexity 
  of 
  the 
  shell. 
  There 
  is 
  only 
  a 
  sliglit 
  

   indication 
  on 
  the 
  ventro-posterior 
  surface 
  of 
  the 
  constricted 
  part 
  as 
  

   noticed 
  in 
  P. 
  vespertina. 
  The 
  posterior 
  adductor 
  muscle 
  (Fig. 
  11, 
  P. 
  A.), 
  

   somewhat 
  ovate-shaped, 
  is 
  situated 
  in 
  the 
  dorsal 
  part 
  at 
  the 
  posterior 
  

   end 
  of 
  the 
  animal, 
  and 
  its 
  ends 
  likewise 
  conform 
  to 
  the 
  convexity 
  

   of 
  the 
  shell. 
  

  

  A 
  lateral 
  view 
  of 
  the 
  retractor 
  pedis 
  anterior 
  muscle 
  shows 
  it 
  to 
  

   be 
  wide 
  dorsally, 
  and 
  tapering 
  ventrally, 
  whilst 
  the 
  retractor 
  pedis 
  

   posterior 
  muscle 
  (Fig. 
  11, 
  P.P. 
  P.) 
  is 
  perhaps 
  shorter 
  and 
  thicker 
  

  

  