﻿108 
  PKOCUKDINGS 
  OF 
  THE 
  MALACOLOGICAL 
  SOCIlil'Y. 
  

  

  through 
  to 
  the 
  base 
  of 
  the 
  tooth, 
  making 
  the 
  base-line 
  strongly 
  

   waved, 
  are 
  characteristics 
  which 
  point 
  to 
  even 
  closer 
  relationship 
  

   with 
  Morula. 
  

  

  loPAS, 
  H. 
  & 
  A. 
  Adams. 
  

  

  /. 
  sertum, 
  Lam. 
  : 
  Natal. 
  Ehachidian 
  very 
  thick, 
  dark 
  chestnut 
  

   colour 
  in 
  the 
  adult 
  ; 
  central 
  cusp 
  very 
  long, 
  narrow, 
  and 
  thick, 
  

   with 
  a 
  central 
  tube, 
  deeply 
  set 
  in 
  a 
  shallow 
  pit 
  on 
  the 
  upper 
  

   margin, 
  in 
  quite 
  a 
  different 
  plane 
  to 
  the 
  two 
  side 
  cusps, 
  root 
  

   carried 
  through 
  to 
  the 
  base 
  and 
  slightly 
  projecting 
  ; 
  side 
  cusps 
  

   small, 
  sharp, 
  triangular, 
  inclining 
  inwards; 
  tliey 
  vary 
  greatly 
  in 
  

   size 
  in 
  different 
  specimens, 
  being 
  sometimes 
  long 
  and 
  sharp 
  (Samoa), 
  

   sometimes 
  quite 
  small 
  and 
  blunt 
  (Berbera) 
  ; 
  their 
  inner 
  side 
  and 
  root 
  

   descend 
  well 
  below 
  the 
  upper 
  margin. 
  Of 
  two 
  specimens 
  from 
  

   Durban 
  (H. 
  C. 
  Burnup, 
  as 
  situla, 
  Reeve), 
  one 
  has 
  side 
  cusps 
  long 
  

   and 
  prominent, 
  another 
  has 
  scarcely 
  any 
  trace 
  of 
  thera 
  at 
  all, 
  and 
  

   that 
  only 
  in 
  a 
  few 
  rows. 
  No 
  inner 
  or 
  external 
  denticles, 
  no 
  knob. 
  

   In 
  a 
  specimen 
  from 
  Samoa 
  there 
  is 
  in 
  many 
  of 
  the 
  teeth 
  a 
  small 
  

   blunt 
  denticle 
  Ij'ing 
  close 
  to 
  the 
  inner 
  base 
  of 
  the 
  side 
  cusps; 
  this 
  is 
  

   quite 
  an 
  irregular 
  growth, 
  and 
  in 
  the 
  specimen 
  concerned 
  occurs 
  

   sometimes 
  on 
  one 
  side 
  only; 
  in 
  part 
  of 
  the 
  radula 
  it 
  is 
  absent 
  

   altogether. 
  Of 
  three 
  specimens 
  from 
  Hilo, 
  two 
  show 
  no 
  trace 
  of 
  

   this 
  smaller 
  denticle, 
  one 
  shows 
  it 
  plainly, 
  in 
  certain 
  portions 
  of 
  

   the 
  radula 
  only. 
  The 
  base 
  is 
  deep 
  and 
  rounded, 
  with 
  a 
  slight 
  

   projection 
  — 
  not 
  seen 
  in 
  all 
  specimens 
  — 
  where 
  the 
  root 
  of 
  the 
  central 
  

   cusp 
  reaches 
  it. 
  (Fig. 
  34.) 
  

  

  I 
  cannot 
  agree 
  with 
  Troschel 
  in 
  placing 
  this 
  genus 
  near 
  to 
  

   patula, 
  L. 
  

  

  Vexilla, 
  Swainson. 
  

  

  This 
  genus, 
  as 
  represented 
  in 
  the 
  Gwatkin 
  collections, 
  raises 
  some 
  

   difficult 
  problems. 
  I 
  simply 
  record 
  the 
  facts, 
  in 
  the 
  hope 
  that 
  the 
  

   investigation 
  of 
  further 
  material 
  may 
  throw 
  more 
  light. 
  

  

  taniata, 
  Powis 
  : 
  Sandwich 
  Is. 
  Central 
  cusp 
  very 
  thick 
  and 
  

   long, 
  a 
  single 
  little 
  denticle 
  in 
  place 
  of 
  a 
  side 
  cusp 
  on 
  each 
  side 
  ; 
  no 
  

   outer 
  denticles, 
  no 
  knob; 
  base 
  oblong, 
  deep, 
  somewliat 
  arched 
  

   below 
  ; 
  laterals 
  extraordinarily 
  long, 
  slightly 
  serrated, 
  serrse 
  

   numerous, 
  except 
  at 
  tip. 
  A 
  Cambridge 
  specimen 
  from 
  the 
  same 
  

   source 
  corresponds 
  as 
  far 
  as 
  the 
  laterals 
  go 
  ; 
  details 
  of 
  rhachidian 
  are 
  

   not 
  visible, 
  as 
  it 
  is 
  tipped 
  on 
  one 
  side 
  on 
  the 
  slide. 
  (Fig. 
  35.) 
  

  

  vexillum, 
  Chem. 
  There 
  are 
  three 
  specimens 
  in 
  the 
  British 
  Museum 
  

   Collection. 
  

  

  Specimen 
  1 
  : 
  Mauritius 
  (Sow.). 
  Rhachidian 
  witli 
  a 
  very 
  long, 
  

   thick, 
  and 
  strong 
  median 
  cusp, 
  deeply 
  rooted, 
  close 
  to 
  which, 
  on 
  

   each 
  side, 
  is 
  a 
  small 
  bluntisb 
  denticle, 
  deeply 
  rooted 
  ; 
  base 
  somewhat 
  

   rounded 
  at 
  the 
  sides 
  and 
  arched 
  below, 
  divided 
  crosswise 
  by 
  a 
  

   continuous 
  line, 
  above 
  which 
  tlie 
  mass 
  of 
  the 
  tooth 
  is 
  thick, 
  and 
  

   below 
  it 
  transparent 
  ; 
  laterals 
  narrow 
  at 
  the 
  tip, 
  roughly 
  serrated, 
  

   serrse 
  few. 
  (Fig. 
  36.) 
  

  

  Specimen 
  2: 
  Isipingo 
  (H. 
  C. 
  Burnup). 
  Generally 
  similar 
  to 
  

   specimen 
  1, 
  except 
  that 
  the 
  median 
  cusp 
  is 
  not 
  so 
  long 
  or 
  thick, 
  the 
  

  

  