﻿COOKE 
  : 
  ON 
  THE 
  KADULA 
  OF 
  COMINELLA. 
  229 
  

  

  IL 
  The 
  Cape 
  group 
  of 
  species 
  is 
  distinguislied 
  by 
  two 
  very 
  marked 
  

   types 
  of 
  radula. 
  

  

  (rt) 
  Khachidian 
  tooth 
  rather 
  bluntly 
  tricuspid, 
  base 
  deep 
  and 
  

   squarish, 
  arched 
  below, 
  no 
  wings; 
  laterals 
  tricuspid, 
  the 
  smaller 
  

   inner 
  cusp 
  in 
  the 
  Austro-Neozealanian 
  group 
  being 
  replaced 
  by 
  a 
  

   two-denticled 
  cusp, 
  simple, 
  deeply 
  cut. 
  

  

  ib) 
  Khachidian 
  tooth 
  bluntly 
  long 
  oblong, 
  base 
  slightly 
  arched 
  

   below, 
  angled 
  in 
  front, 
  set 
  with 
  a 
  number 
  (4-7) 
  of 
  small 
  sharp 
  

   denticles, 
  laterals 
  quadricuspid, 
  large, 
  cusps 
  boldly 
  curved, 
  the 
  three 
  

   inner 
  forming 
  a 
  group, 
  of 
  which 
  the 
  central 
  is 
  much 
  the 
  largest. 
  

  

  I 
  have 
  counted 
  in 
  

  

  delalandii 
  112 
  + 
  rows 
  of 
  teetl^ 
  limhosa 
  116 
  rows 
  of 
  teeth. 
  

   elongata 
  109 
  ,, 
  porcata 
  116 
  ,, 
  

  

  lagenaria 
  120 
  ,, 
  tig 
  r 
  ma 
  95-|- 
  ,, 
  

  

  Special 
  features 
  of 
  thu 
  various 
  species. 
  

   Group 
  («). 
  

  

  elongata. 
  — 
  Cusps 
  of 
  the 
  rhachidian 
  tooth 
  not 
  much 
  elevated 
  above 
  

   the 
  upper 
  edge 
  of 
  the 
  base; 
  base 
  deep, 
  pinched 
  in 
  at 
  the 
  sides 
  and 
  

   slightly 
  arched 
  below; 
  lateral 
  tricuspid, 
  the 
  two 
  inner 
  cusps 
  very 
  

   close 
  together, 
  deeply 
  cut. 
  

  

  tigrina. 
  — 
  Cusps 
  of 
  the 
  rhachidian 
  tooth 
  considerably 
  elevated 
  

   above 
  the 
  upper 
  edge 
  of 
  the 
  base, 
  the 
  two 
  outer 
  cusps 
  set 
  at 
  an 
  angle 
  

   with 
  the 
  central 
  ; 
  base 
  markedly 
  angulated 
  at 
  its 
  upper 
  edge, 
  pinched 
  

   at 
  the 
  sides, 
  deeply 
  arched 
  below; 
  lateral 
  tricuspid, 
  the 
  two 
  inner 
  

   cusps 
  further 
  away 
  from 
  another 
  than 
  in 
  elongata^ 
  not 
  so 
  deeply 
  cut. 
  

  

  Group 
  (i). 
  

  

  delalandii. 
  — 
  Rhachidian 
  tooth 
  with 
  four 
  denticles; 
  base 
  angulated 
  

   at 
  the 
  upper 
  edge, 
  slightly 
  arched 
  below; 
  lateral 
  showing 
  no 
  sign 
  of 
  

   denticulation 
  on 
  any 
  of 
  the 
  cusps, 
  exterior 
  of 
  the 
  three 
  interior 
  cusps 
  

   large, 
  central 
  very 
  large, 
  curved 
  over 
  the 
  interior 
  cusp, 
  which 
  is 
  very 
  

   small, 
  not 
  serrated. 
  

  

  lagenaria. 
  — 
  llhachidian 
  tooth 
  with 
  seven 
  denticles 
  ; 
  upper 
  edge 
  of 
  

   base 
  slightly 
  produced 
  at 
  the 
  ends, 
  base 
  considerably 
  arched; 
  in 
  the 
  

   laterals 
  the 
  interior 
  cusp 
  shows 
  signs 
  of 
  serrations 
  on 
  the 
  outer 
  edge, 
  

   the 
  exterior 
  cusp 
  of 
  tlie 
  group 
  of 
  three 
  is 
  very 
  small, 
  curiously 
  curved 
  

   inward. 
  

  

  limhosa. 
  — 
  llhachidian 
  tooth 
  with 
  six 
  denticles 
  ; 
  base 
  squarely 
  

   oblong, 
  slightly 
  rounded 
  at 
  upper 
  angles, 
  lower 
  edge 
  scarcely 
  arched 
  ; 
  

   both 
  the 
  exterior 
  and 
  interior 
  cusps 
  of 
  the 
  group 
  of 
  three 
  large, 
  blunt, 
  

   the 
  interior 
  slightly 
  serrated 
  on 
  the 
  inner 
  edge. 
  

  

  porcata. 
  — 
  Denticles 
  of 
  the 
  rhachidian 
  tooth 
  six 
  in 
  number, 
  rather 
  

   larger 
  than 
  in 
  the 
  other 
  species 
  ; 
  base 
  with 
  the 
  upper 
  angles 
  rounded, 
  

   very 
  slightly 
  arched 
  below 
  ; 
  interior 
  cusp 
  of 
  the 
  group 
  of 
  three 
  very 
  

   large, 
  with 
  faint 
  traces 
  of 
  serration 
  on 
  the 
  inner 
  side, 
  exterior 
  cusp 
  of 
  

   this 
  group 
  small 
  and 
  narrow. 
  In 
  some 
  of 
  the 
  laterals 
  there 
  are 
  clear 
  

   traces 
  of 
  a 
  supplementary 
  denticle 
  or 
  knob, 
  between 
  the 
  tricuspid 
  

   • 
  inner 
  tooth 
  and 
  the 
  great 
  outer 
  cusp. 
  

  

  