﻿319 
  

  

  ON 
  THE 
  VALUE 
  OF 
  THE 
  GASTROPOD 
  APEX 
  IN 
  CLASSIFICATION. 
  

  

  By 
  Tom 
  Ikedalk. 
  

  

  Bead 
  10th 
  March, 
  1911. 
  

  

  In 
  the 
  Proc. 
  Malac. 
  Soc, 
  vol. 
  ix, 
  p. 
  74, 
  1910, 
  I 
  recorded, 
  the 
  

   occurrence 
  of 
  the 
  Sinusigera 
  apex 
  in 
  species 
  of 
  Alectrion, 
  and 
  sug- 
  

   gested 
  it 
  would 
  prove 
  a 
  valuable 
  aid 
  to 
  the 
  future 
  monographer 
  of 
  

   that 
  difficult 
  group. 
  Since 
  then 
  I 
  have 
  carefully 
  searched 
  through 
  all 
  

   my 
  Kermadec 
  material 
  (unfortunately 
  very 
  scant), 
  simply 
  examining 
  

   every 
  juvenile 
  specimen, 
  with 
  quite 
  surprising 
  results. 
  I 
  will 
  here 
  

   detail 
  the 
  facts 
  before 
  touching 
  upon 
  the 
  lessons 
  which 
  seem 
  to 
  be 
  

   pointed 
  out. 
  

  

  My 
  first 
  find 
  was 
  a 
  juvenile 
  Mitra, 
  of 
  which 
  I 
  had 
  obtained 
  no 
  

   adults, 
  which 
  clearly 
  showed 
  the 
  apex 
  to 
  be 
  Sinusigera. 
  A 
  much 
  

   more 
  elongate 
  Sinusigera 
  was 
  found 
  attached 
  to 
  a 
  couple 
  of 
  post- 
  

   embryonic 
  whorls, 
  which 
  led 
  to 
  its 
  identification 
  as 
  the 
  young 
  of 
  

   Turris 
  cingulifera, 
  Lamk. 
  Some 
  of 
  my 
  smaller 
  Turrids 
  had 
  been 
  noted 
  

   as 
  possessing 
  many-whorled 
  protoconchs, 
  and 
  examination 
  elicited 
  

   their 
  Sinusigera 
  character. 
  These 
  were 
  specimens 
  of 
  the 
  unizonalis, 
  

   Lamk., 
  group, 
  and 
  this 
  group 
  has 
  been 
  usually 
  referred 
  to 
  Drillia. 
  

   Figures 
  of 
  Gly2)hostoma 
  and 
  Clathurella 
  insinuate 
  the 
  occurrence 
  of 
  

   Sinusigera 
  apices 
  in 
  these 
  genera. 
  Dall 
  has 
  recently 
  written 
  (Bull. 
  

   Mus. 
  Comp. 
  Zool. 
  Harvard, 
  vol. 
  xliii, 
  p. 
  260, 
  1908), 
  "The 
  nucleus 
  

   of 
  Daphnella, 
  on 
  the 
  other 
  hand, 
  is 
  a 
  typical 
  ' 
  Sinusigera 
  \'''' 
  and 
  of 
  

   £uhela 
  (same 
  page), 
  "nucleus 
  of 
  the 
  Sinusigera 
  type." 
  Throughout 
  

   that 
  paper 
  Dall 
  appears 
  to 
  attach 
  importance 
  to 
  the 
  features 
  of 
  tlie 
  

   apex 
  in 
  the 
  Turritidae, 
  though 
  twentj^ 
  years 
  previously 
  he 
  had 
  

   concluded 
  (same 
  journal, 
  vol. 
  xviii, 
  p. 
  75), 
  " 
  as 
  far 
  as 
  our 
  knowledge 
  

   goes, 
  nuclear 
  characters 
  have 
  little 
  absolute 
  systematic 
  value 
  in 
  this 
  

   group, 
  and 
  their 
  relative 
  value 
  remains 
  to 
  be 
  determined." 
  I 
  anticipate 
  

   that 
  study 
  of 
  the 
  apices 
  will 
  provide 
  the 
  solution 
  of 
  the 
  intricate 
  

   problem 
  presented 
  by 
  this 
  group 
  of 
  molluscs. 
  

  

  Inasmuch 
  as 
  the 
  majority 
  of 
  the 
  larger 
  molluscs 
  met 
  with 
  at 
  the 
  

   Kermadecs 
  clearly 
  indicated 
  their 
  arrival 
  as 
  juveniles 
  by 
  means 
  of 
  

   free-swimming 
  larvae, 
  the 
  only 
  large 
  Columhella 
  found 
  was 
  examined, 
  

   and 
  at 
  once 
  a 
  Sinusigera 
  was 
  observed. 
  The 
  apex 
  of 
  Terehra 
  has 
  

   been 
  constantly 
  noted, 
  but 
  its 
  Sinusigera 
  character 
  appears 
  to 
  have 
  

   escaped 
  attention. 
  Thus, 
  as 
  regards 
  the 
  Sinusigera, 
  at 
  Sunday 
  Island 
  

   I 
  have 
  traced 
  it 
  in 
  the 
  families 
  Mitridse, 
  Buccinidse, 
  Alectrionidse, 
  

   Thaitidae, 
  Columbellidae, 
  Coralliophilidae, 
  Turritidse, 
  and 
  Terebridae. 
  

  

  Craven, 
  in 
  his 
  Monographie 
  du 
  genre 
  Sinusigera, 
  D'Orb. 
  (Ann. 
  

   Soc. 
  Roy. 
  Malac. 
  Belg., 
  vol. 
  xii, 
  pp. 
  105 
  et 
  seq., 
  1877), 
  describes 
  and 
  

   figures 
  many 
  diverse 
  forms 
  of 
  Sinusigera. 
  I 
  cannot 
  yet 
  definitely 
  

   locate 
  some 
  of 
  his 
  figures, 
  but 
  one 
  is 
  undoubtedly 
  the 
  apex 
  of 
  a 
  species 
  

   of 
  Triphora, 
  as 
  was 
  afterwards 
  admitted 
  by 
  Craven 
  himself. 
  This 
  led 
  

   Fischer 
  to 
  write 
  (Manuel 
  Conch., 
  p. 
  651, 
  1884) 
  : 
  " 
  On 
  a 
  compris 
  dans 
  

   ce 
  genre 
  des 
  embryons 
  de 
  Cerithium, 
  de 
  Triforis, 
  de 
  divers 
  genres 
  de 
  

   Taenioglosses, 
  et 
  peut-etre 
  aussi 
  de 
  Rhachiglosses 
  {Purpura). 
  I.a 
  

  

  