﻿MOLLUSCA. 
  107 
  

  

  given 
  bjr 
  Quoy 
  and 
  Gaimard 
  of 
  their 
  Psammohia 
  vitrea 
  and 
  with 
  the 
  

   figure 
  in 
  Mobius's 
  work 
  above 
  referred 
  to, 
  pi. 
  xxi, 
  figs. 
  10 
  a, 
  h. 
  The 
  

   foot 
  protrudes 
  at 
  the 
  narrower 
  end 
  of 
  the 
  shell 
  ; 
  it 
  is 
  small 
  when 
  

   retracted, 
  of 
  a 
  boot-like 
  form, 
  roundly 
  carinate 
  at 
  the 
  base, 
  pointed 
  

   at 
  the 
  tip, 
  and 
  furnished 
  with 
  what 
  is 
  probably 
  a 
  byssiferous 
  process 
  

   at 
  the 
  posterior 
  end 
  (" 
  talon," 
  Q. 
  & 
  G.) 
  ; 
  this 
  is 
  of 
  an 
  opaque 
  white 
  

   colour. 
  The 
  mantle 
  is 
  open 
  in 
  front 
  and 
  the 
  anterior 
  half 
  of 
  the 
  

   ventral 
  margin 
  for 
  the 
  passage 
  of 
  the 
  foot, 
  and 
  united 
  along 
  the 
  

   rest 
  of 
  the 
  basal 
  and 
  hinder 
  margins, 
  where 
  there 
  is 
  a 
  minute 
  

   siphonal 
  perforation. 
  The 
  surface 
  of 
  the 
  mantle 
  beneath 
  is 
  covered 
  

   with 
  papillae, 
  and 
  the 
  membranous 
  marginal 
  expansion 
  in 
  life 
  pro- 
  

   bably 
  covers 
  nearly 
  the 
  entire 
  surface 
  of 
  the 
  shell, 
  for 
  even 
  in 
  spirit 
  

   specimens 
  it 
  still 
  extends 
  halfway 
  up 
  the 
  valves. 
  There 
  are 
  two 
  

   labial 
  palpi 
  on 
  each 
  side. 
  From 
  this 
  description 
  the 
  close 
  relation- 
  

   ship 
  with 
  Galeomma 
  is 
  very 
  apparent. 
  

  

  The 
  dentition 
  of 
  this 
  species, 
  according 
  to 
  my 
  observation, 
  does 
  

   not 
  agree 
  with 
  the 
  description 
  given 
  by 
  Deshayes. 
  In 
  the 
  right 
  

   valve 
  I 
  find 
  a 
  prominent 
  tooth 
  a 
  little 
  in 
  front 
  of 
  the 
  beak, 
  and 
  a 
  

   second 
  more 
  remote 
  behind 
  it 
  ; 
  the 
  left 
  valve 
  has 
  two 
  teeth, 
  of 
  

   which 
  the 
  anterior 
  is 
  the 
  smaller, 
  just 
  beneath 
  the 
  umbo, 
  and 
  a 
  

   third 
  a 
  little 
  behind 
  it. 
  The 
  ligament 
  is 
  externally 
  visible, 
  being 
  

   attached 
  to 
  the 
  hinge-line 
  above 
  the 
  teeth, 
  a 
  portion 
  of 
  it 
  being 
  

   internal 
  above 
  and 
  between 
  the 
  teeth. 
  

  

  48. 
  Scintilla 
  alberti. 
  (Plate 
  VII. 
  figs. 
  G, 
  G 
  1.) 
  

  

  Shell 
  small, 
  pellucid, 
  milky 
  white, 
  considerably 
  inequilateral, 
  

   transversely 
  oblong, 
  shorter 
  and 
  narrower 
  in 
  front 
  of 
  the 
  iimbones 
  

   than 
  behind 
  them, 
  moderately 
  swollen. 
  Lateral 
  and 
  dorsal 
  mar- 
  

   gins 
  curved, 
  ventral 
  rather 
  rectilinear. 
  Surface 
  glossy, 
  exhibiting 
  

   (under 
  the 
  lens) 
  distinct 
  concentric 
  lines 
  of 
  growth 
  and 
  also 
  minute 
  

   radiating 
  and 
  somewhat 
  interrupted 
  striaj, 
  visible 
  oulj^ 
  under 
  a 
  

   compound 
  microscope. 
  Ilmbones 
  small, 
  slightly 
  elevated 
  above 
  the 
  

   hinge-margin, 
  not 
  quite 
  adjacent, 
  the 
  valves 
  being 
  closed. 
  Cardinal 
  

   teeth 
  insignificant, 
  consisting 
  of 
  a 
  single 
  subumboual 
  denticular 
  

   slight 
  obtuse 
  prominence, 
  which 
  is 
  more 
  distinct 
  in 
  the 
  left 
  than 
  in 
  

   the 
  right 
  valve. 
  Ligament 
  small, 
  visible 
  externally, 
  extending 
  on 
  

   both 
  cides 
  of 
  the 
  apices 
  of 
  the 
  beaks, 
  but 
  further 
  posteriorly 
  than 
  in 
  

   front. 
  Height 
  5^ 
  millim., 
  width 
  -i, 
  length 
  7f. 
  

  

  Hah. 
  West 
  Island, 
  Prince 
  of 
  Wales 
  Channel, 
  Torres 
  Straits 
  

   ( 
  Coppinger). 
  

  

  S. 
  liydatina, 
  Deshayes, 
  appears 
  to 
  be 
  more 
  closely 
  related 
  to 
  this 
  

   species 
  than 
  to 
  any 
  other 
  in 
  the 
  genus. 
  It 
  is, 
  however, 
  higher, 
  more 
  

   equilateral, 
  flatter, 
  with 
  more 
  equal 
  sides 
  and 
  a 
  curved 
  ventral 
  

   margin. 
  

  

  49. 
  Crassatella 
  pulchra. 
  

  

  Reeve, 
  Conch. 
  Icon. 
  fig. 
  IG. 
  

  

  Hah. 
  Thursday 
  Island, 
  Torres 
  Straits, 
  3-4 
  fms. 
  (Oopjnnger) 
  ; 
  Port 
  

   Essington 
  {Capt. 
  WicMiam, 
  li.N., 
  in 
  Brit. 
  Mus.). 
  

  

  