﻿COOKE 
  : 
  ON 
  POSITION 
  OF 
  ZESIIIiA. 
  1 
  3 
  

  

  separate 
  aud 
  equidistant 
  from 
  one 
  another, 
  set 
  on 
  the 
  upper 
  margin 
  

   of 
  the 
  tooth, 
  but 
  not 
  deeply 
  rooted 
  in 
  it. 
  The 
  base 
  is 
  wide 
  and 
  

   narrow, 
  the 
  upper 
  margin 
  continued 
  beyond 
  the 
  two 
  outer 
  cusps, 
  

   sharply 
  curved 
  in 
  at 
  tlie 
  sides, 
  slightly 
  angularly 
  projecting 
  upwards 
  

   at 
  the 
  upper 
  corners, 
  very 
  slightly 
  arched 
  below, 
  curve 
  of 
  base 
  and 
  

   upper 
  margin 
  exactly 
  parallel. 
  In 
  one 
  specimen 
  the 
  side 
  cusp 
  on 
  the 
  

   left 
  is 
  slightly 
  nearer 
  to 
  the 
  central 
  cusp 
  tlian 
  that 
  on 
  the 
  right. 
  

   The 
  laterals 
  are 
  single-bladed 
  on 
  a 
  rather 
  broad 
  base, 
  blades 
  sharp 
  

   but 
  not 
  narrow, 
  broadening 
  out 
  widely 
  as 
  they 
  approach 
  the 
  base 
  ; 
  

   witliout 
  any 
  sign 
  of 
  denticles 
  (see 
  figure). 
  

  

  The 
  type 
  of 
  radulais 
  thus 
  widely 
  different 
  from 
  that 
  of 
  Latrtincidus, 
  

   and 
  stands 
  quite 
  by 
  itself. 
  The 
  only 
  radulse 
  at 
  all 
  comparable 
  to 
  it 
  

   are 
  those 
  of 
  Oliva 
  and 
  Murex. 
  Oliva 
  shows, 
  in 
  the 
  rhachidian, 
  three 
  

   sharp 
  cusps 
  on 
  a 
  narrow 
  base, 
  but 
  the 
  cusps 
  are 
  much 
  closer 
  together, 
  

   and 
  the 
  central 
  cusp 
  is 
  invariably 
  much 
  smaller 
  than 
  the 
  two 
  side 
  

   cusps 
  ; 
  the 
  curves 
  of 
  the 
  base 
  are 
  also 
  much 
  more 
  pronounced. 
  The 
  

   laterals 
  in 
  Oliva 
  are 
  leg-of-mutton 
  shaped, 
  with 
  the 
  basal 
  angles 
  very 
  

   obtusely 
  angled. 
  

  

  On 
  the 
  other 
  hand, 
  the 
  Zemira 
  radiila 
  is 
  much 
  more 
  closely 
  allied 
  

   to 
  that 
  oi 
  Murex 
  proper, 
  the 
  characteristic 
  of 
  whicli 
  is 
  a 
  tricuspid 
  

   rhachidian 
  tooth, 
  with 
  two 
  much 
  smaller 
  cusps 
  between 
  the 
  externals 
  

   and 
  the 
  central. 
  The 
  three 
  larger 
  cusps 
  approximate 
  closely 
  in 
  

   length, 
  and 
  the 
  base 
  is 
  very 
  nearly 
  that 
  of 
  Zemira 
  (see 
  Troschel, 
  Das 
  

   Gebiss, 
  vol. 
  ii, 
  pi. 
  x, 
  figs. 
  19-21 
  ; 
  pi. 
  xi, 
  figs. 
  1-8). 
  In 
  fact, 
  if 
  you 
  

   take 
  away 
  the 
  two 
  small 
  intermediate 
  cusps 
  in 
  llurex 
  you 
  have 
  

   a 
  rhacliidian 
  tooth 
  most 
  closely 
  allied 
  to 
  that 
  of 
  Zemira, 
  while 
  the 
  

   laterals 
  in 
  both 
  correspond 
  exactly. 
  

  

  On 
  the 
  whole, 
  tlierefore, 
  the 
  evidence 
  of 
  the 
  radula, 
  regarded 
  apart 
  

   from 
  all 
  other 
  considerations, 
  conchological 
  or 
  otherwise, 
  points 
  

   unmistakably 
  to 
  a 
  classification 
  of 
  Zemira 
  wliich 
  will 
  remove 
  it 
  from 
  

   Latrunculus 
  and 
  place 
  it 
  near 
  to 
  Murex. 
  This 
  will 
  involve 
  giving 
  it 
  

   generic 
  instead 
  of 
  subgeneric 
  rank. 
  

  

  The 
  specimens 
  of 
  the 
  radula 
  of 
  Zemira 
  which 
  I 
  have 
  been 
  able 
  to 
  

   examine 
  are 
  all 
  from 
  the 
  mounting 
  of 
  the 
  late 
  Professor 
  H. 
  M. 
  

   Gwatkin. 
  One 
  is 
  in 
  the 
  collection 
  at 
  the 
  Natural 
  History 
  Museum, 
  

   Soutli 
  Kensington, 
  one 
  in 
  the 
  Museum 
  of 
  Zoology, 
  Cambridge, 
  and 
  

   one 
  in 
  mj- 
  own 
  possession. 
  

  

  The 
  exact 
  geographical 
  limits 
  of 
  the 
  distribution 
  of 
  Zemira 
  have 
  

   yet 
  to 
  be 
  laid 
  down. 
  The 
  British 
  Museum 
  has 
  four 
  specimens 
  from 
  

   Port 
  Jackson, 
  three 
  of 
  which 
  are 
  from 
  the 
  Cuming 
  Museum, 
  the 
  

   fouith 
  from 
  the 
  Sow 
  and 
  Pigs 
  Eeefs 
  (Brazier), 
  and 
  also 
  specimens 
  

   obtained 
  by 
  the 
  Challenger 
  from 
  Port 
  Jackson 
  (6-7 
  fathoms), 
  

   and 
  from 
  off 
  East 
  Moncour 
  Island, 
  Bass 
  Straits 
  (38 
  fathoms). 
  

   The 
  McAndrew 
  Collection 
  at 
  Cambridge 
  has 
  specimens 
  from 
  Lake 
  

   Macquarie, 
  Tenison 
  Woods 
  (" 
  Census 
  of 
  the 
  Marine 
  Shells 
  of 
  

  

  