﻿COOKE: 
  A 
  COLONY 
  OF 
  KVCELLA 
  LAPILLUS. 
  231 
  

  

  Group 
  1 
  exhibits 
  teeth 
  of 
  a 
  very 
  simple 
  character. 
  Group 
  2 
  is 
  

   closely 
  allied 
  to 
  Group 
  1, 
  the 
  most 
  marked 
  point 
  of 
  contrast 
  being 
  

   the 
  bifid 
  cusp 
  in 
  the 
  lateral. 
  Group 
  3 
  is 
  by 
  far 
  the 
  most 
  specialized 
  

   as 
  regards 
  radula, 
  and, 
  while 
  preserving 
  a 
  certain 
  tie 
  of 
  kinship, 
  

   stands 
  well 
  apart 
  from 
  the 
  other 
  two, 
  both 
  as 
  regards 
  shape 
  and 
  

   deuticulation 
  of 
  the 
  rhachidian 
  and 
  in 
  the 
  elaboration 
  of 
  the 
  cusps 
  of 
  

   the 
  laterals. 
  

  

  It 
  is 
  hoped 
  that 
  the 
  facts 
  now 
  brought 
  together 
  may 
  be 
  of 
  use, 
  as 
  

   throwing 
  light 
  on 
  the 
  general 
  inter-affinities 
  of 
  the 
  group 
  as 
  a 
  whole, 
  

   and 
  possibly 
  on 
  the 
  vexed 
  question 
  of 
  distinction 
  of 
  species. 
  

  

  EXPLANATION 
  OF 
  FIGUKES. 
  

   Fig. 
  

  

  1. 
  Coininella 
  adelaidensis, 
  Crosse: 
  Australia. 
  

  

  2. 
  ,, 
  alveolata, 
  Kien. 
  {= 
  lineolata, 
  Jjum.) 
  : 
  Port 
  Phillip. 
  

  

  3. 
  ,, 
  eburiiea, 
  B,ee\e 
  ( 
  = 
  costata, 
  Qnoy) 
  : 
  New 
  Zealand. 
  

  

  4. 
  ,, 
  filicea, 
  Cr. 
  & 
  Fisch. 
  : 
  Port 
  Jackson. 
  

  

  5. 
  ,, 
  quoyana, 
  A. 
  Ad. 
  (= 
  huttoni, 
  Kob.) 
  : 
  New 
  Zealand. 
  

  

  6. 
  ,, 
  Imeolata, 
  Lam. 
  : 
  Tasmania. 
  

  

  7. 
  ,, 
  lurida, 
  Phil. 
  : 
  New 
  Zealand. 
  

  

  8. 
  ,, 
  adspersa.BxuQ. 
  { 
  = 
  viactilata,'i,ia,xi.): 
  New 
  Zealand. 
  

  

  9. 
  ,, 
  maculosa, 
  Mart. 
  : 
  New 
  Zealand. 
  

  

  10. 
  ,, 
  virgata, 
  H. 
  & 
  A. 
  Ad. 
  : 
  New 
  Zealand. 
  

  

  11. 
  ,, 
  elongata, 
  Dunk. 
  : 
  Cape 
  of 
  Good 
  Hope. 
  

  

  12. 
  ,, 
  tigrina, 
  Kien. 
  : 
  South 
  Africa. 
  

  

  13. 
  , 
  ,, 
  delalandii, 
  Kien. 
  : 
  St. 
  James', 
  Cape 
  Town. 
  

  

  14. 
  ,, 
  lagenaria, 
  Lam. 
  : 
  Cape 
  of 
  Good 
  Hope. 
  

  

  15. 
  ,, 
  limbosa, 
  Lam. 
  : 
  Sea 
  Point, 
  Cape 
  Town. 
  

  

  16. 
  ,, 
  ^jorcato, 
  Gmel. 
  : 
  Algoa 
  Bay. 
  

  

  A 
  COLONY 
  OF 
  NUCELLA 
  (OLIM 
  PURPURA) 
  LAPILLUS 
  (LINN.) 
  

   WITH 
  OPERCULUM 
  MALFORMED 
  OR 
  ABSENT. 
  

  

  By 
  the 
  Eev. 
  A. 
  H. 
  Cooke, 
  Sc.D., 
  F.Z.S. 
  

  

  Read 
  9th 
  March, 
  1917. 
  

  

  Visiting 
  Lydstep 
  (a 
  few 
  miles 
  west 
  of 
  Tenby) 
  in 
  August, 
  1915, 
  at 
  

   a 
  very 
  low 
  tide, 
  I 
  took 
  a 
  living 
  specimen 
  of 
  N. 
  lapillus 
  off 
  the 
  face 
  

   of 
  the 
  cliff, 
  and 
  observed 
  that 
  it 
  had 
  no 
  operculum. 
  Thinking 
  that 
  

   perhaps 
  the 
  act 
  of 
  pulling 
  the 
  specimen 
  off 
  the 
  rock 
  had 
  torn 
  the 
  

   operculum 
  away, 
  I 
  examined 
  further 
  specimens, 
  with 
  the 
  result 
  

   that 
  it 
  appeared 
  that 
  this 
  particular 
  colony 
  of 
  Nucella 
  were 
  suffering, 
  

   to 
  a 
  considerable 
  extent, 
  from 
  malformation 
  of 
  the 
  organ. 
  

   Of 
  121 
  specimens 
  examined, 
  

  

  (1) 
  The 
  operculum 
  was 
  more 
  or 
  less 
  perfect 
  in 
  54. 
  

  

  (2) 
  ,, 
  ,, 
  decidedly 
  imperfect 
  in 
  56. 
  

  

  (3) 
  ,, 
  ,, 
  absent 
  altogether 
  in 
  11. 
  

  

  In 
  class 
  2 
  the 
  imperfection 
  was 
  not 
  always 
  of 
  the 
  same 
  nature. 
  

   Sometimes 
  the 
  operculum 
  was 
  considerably 
  reduced 
  in 
  size, 
  so 
  that, 
  

   when 
  the 
  animal 
  was 
  withdrawn, 
  only 
  a 
  portion 
  of 
  the 
  aperture 
  was 
  

   covered. 
  Occasionally 
  the 
  operculum 
  was 
  perfect 
  as 
  regards 
  size, 
  

   but 
  was 
  thin, 
  and 
  of 
  a 
  very 
  light 
  horn 
  colour, 
  almost 
  white, 
  instead 
  

  

  