﻿MOLLUSC 
  A. 
  39 
  

  

  6. 
  Pleurotoma 
  (Glyphostoma) 
  spurca. 
  (Plate 
  IV. 
  figs. 
  F-F 
  1.) 
  

  

  Clavatula 
  spurca, 
  Himh, 
  Voy, 
  ' 
  Sulphur,'' 
  p. 
  17, 
  pi. 
  5. 
  fig. 
  14 
  ; 
  Reeve, 
  

  

  Conch. 
  Icon. 
  fig. 
  312. 
  

   Pleurotoma 
  rava, 
  JReeve 
  (non 
  Hinds), 
  Conch. 
  Icon. 
  fig. 
  250. 
  

  

  Hab. 
  Port 
  Molle, 
  Arafura 
  Sea, 
  N. 
  Australia, 
  32-36 
  fms., 
  and 
  

   Port 
  Darwin, 
  N.W. 
  Australia 
  ( 
  Coppinger). 
  

  

  This 
  interesting 
  species 
  is 
  subject 
  to 
  considerable 
  variation 
  both 
  

   in 
  form 
  and 
  sculpture, 
  but 
  is 
  nevertheless 
  generally 
  very 
  easily 
  

   recognized 
  by 
  the 
  transverse 
  plaits 
  on 
  the 
  columella 
  and 
  the 
  large 
  

   deep 
  and 
  laterally 
  directed 
  sinus 
  near 
  the 
  upper 
  end 
  of 
  the 
  much 
  

   thickened 
  labrum, 
  which 
  is 
  armed 
  within 
  with 
  five 
  or 
  six 
  denticles 
  

   or 
  short 
  limp 
  not 
  reaching 
  the 
  crenulated 
  edge. 
  The 
  basal 
  canal 
  is 
  

   contracted 
  and 
  a 
  little 
  recurved. 
  The 
  type 
  has 
  ten 
  costoe 
  upon 
  the 
  

   last 
  whorl, 
  but 
  this 
  number 
  is 
  sometimes 
  exceeded 
  by 
  two 
  more. 
  

   The 
  principal 
  lirse 
  are 
  normalljr 
  two 
  in 
  number 
  upon 
  the 
  upper 
  

   volutions, 
  one 
  being 
  at 
  the 
  middle, 
  the 
  other 
  below, 
  nodulous 
  upon 
  

   the 
  costse. 
  Above 
  these, 
  occupying 
  the 
  upper 
  part 
  of 
  the 
  whorls, 
  

   are 
  a 
  few 
  uninterrupted 
  thread-like 
  lira3, 
  about 
  four 
  upon 
  the 
  

   penultimate 
  and 
  antepenultimate 
  whorls. 
  The 
  body-whorl 
  has 
  

   about 
  fifteen 
  principal 
  spiral 
  lirse, 
  two 
  of 
  which 
  pass 
  above 
  the 
  

   extremity 
  of 
  the 
  outer 
  lip. 
  Some 
  varieties 
  have 
  three 
  or 
  even 
  four 
  

   subequal 
  principal 
  lirte 
  on 
  the 
  lower 
  half 
  of 
  the 
  upper 
  whorls, 
  and 
  

   twenty 
  to 
  twenty-four 
  upon 
  the 
  last, 
  but 
  all 
  agree 
  in 
  having 
  the 
  

   finer 
  lines 
  above, 
  which 
  also 
  at 
  times 
  exceed 
  the 
  typical 
  number. 
  

   The 
  largest 
  specimen 
  considerably 
  exceeds 
  the 
  dimensions 
  of 
  Hinds's 
  

   type. 
  It 
  is 
  ] 
  8 
  millim. 
  in 
  length 
  and 
  6 
  in 
  width, 
  measuring 
  above 
  

   the 
  aperture, 
  which 
  is 
  8 
  long. 
  Another 
  smaller 
  example 
  is 
  re- 
  

   markable 
  for 
  the 
  shortness 
  of 
  the 
  mouth 
  : 
  it 
  is 
  12 
  long, 
  4 
  broad, 
  

   with 
  an 
  aperture 
  4| 
  in 
  length. 
  

  

  7. 
  Pleurotoma 
  ( 
  ?) 
  gracilenta, 
  var. 
  

  

  Pleurotoma 
  gTacilenta, 
  Reeve, 
  Conch. 
  Icon. 
  fig. 
  114. 
  

   Var. 
  = 
  PI. 
  contracta, 
  Reeve, 
  I. 
  c. 
  fig. 
  116. 
  

   Var. 
  = 
  PI. 
  fusoides, 
  Reeve, 
  I. 
  c. 
  fig. 
  349. 
  

  

  Hah. 
  Arafura 
  Sea, 
  N". 
  Australia, 
  32-36 
  fms. 
  ; 
  bottom 
  — 
  sand, 
  mud, 
  

   and 
  shells 
  {Coppinrjer); 
  Philippine 
  Islands 
  (Cuminr/). 
  

  

  This 
  species 
  does 
  not 
  conveniently 
  fall 
  into 
  any 
  of 
  the 
  recognized 
  

   groups 
  of 
  Pleurotomidaj. 
  In 
  form 
  it 
  resembles 
  some 
  species 
  of 
  

   DajyJmelJa, 
  but 
  has 
  not 
  the 
  minutely 
  reticulated 
  nuclear 
  whorls 
  of 
  

   that 
  section, 
  and 
  the 
  labral 
  notch 
  is 
  hardly 
  at, 
  but 
  a 
  trifle 
  below, 
  the 
  

   suture. 
  I 
  fail 
  to 
  perceive 
  any 
  sufficient 
  characters 
  to 
  separate 
  

   specifically 
  the 
  three 
  so-called 
  species 
  described 
  by 
  Keeve 
  ; 
  indeed 
  

   PI. 
  co)itracta 
  and 
  PL 
  fnsoides 
  are 
  all 
  but 
  identical. 
  The 
  type 
  of 
  

   P. 
  gracilenta 
  is 
  a 
  trifle 
  more 
  attenuated 
  than 
  the 
  other 
  two, 
  but 
  

   scarcely 
  differs 
  in 
  any 
  other 
  respect. 
  All 
  are 
  longitudinally 
  costate 
  

   and 
  spirally 
  Urate, 
  the 
  costiB 
  numbering 
  about 
  twelve 
  on 
  a 
  whorl, 
  

   attenuated 
  above 
  at 
  the 
  suture, 
  and 
  becoming 
  obsolete 
  upon 
  the 
  

   body-volution 
  towards 
  the 
  narrowed 
  anterior 
  end 
  ; 
  the 
  principal 
  

  

  