﻿ON 
  THE 
  KADULA 
  OF 
  THE 
  GENUS 
  ACANTHINA, 
  G. 
  FISCHER.^ 
  

   By 
  the 
  Ilev. 
  A. 
  H. 
  Cooke, 
  Sc.D., 
  P.Z.S. 
  

  

  Read 
  9th 
  November, 
  1917. 
  

  

  The 
  genus 
  Acanthma 
  is 
  peculiar 
  to 
  the 
  west 
  coast 
  of 
  America, 
  

   ranging 
  from 
  Bolinas 
  Bay 
  in 
  tlie 
  north 
  to 
  Cape 
  Horn 
  and 
  round 
  to 
  

   the 
  Fallilaiids 
  in 
  the 
  south. 
  The 
  species 
  hitherto 
  known 
  under 
  the 
  

   name 
  fall 
  into 
  three 
  geographical 
  groups. 
  

  

  1. 
  The 
  northern, 
  comprising 
  pcnicilirata, 
  Stearns, 
  puncUdata, 
  

   Sowb., 
  and 
  unicarinala, 
  Sowb., 
  and 
  extending 
  from 
  Bolinas 
  Bay 
  to 
  

   San 
  Diego. 
  

  

  2. 
  The 
  central, 
  with 
  hrevidentata, 
  Wood, 
  gra^idis, 
  Gray, 
  and 
  

   miiricata, 
  Brod., 
  ranging 
  from 
  Lower 
  California 
  (point 
  unknown) 
  to 
  

   Paita, 
  including 
  the 
  Ualapagos. 
  

  

  3. 
  The 
  southern, 
  with 
  calcar\ 
  Martyn, 
  and 
  crassilahrum, 
  Lam. 
  

   (many 
  unite 
  the 
  two 
  as 
  one 
  species), 
  ranging 
  from 
  Peru 
  southward, 
  

   round 
  to 
  the 
  Falklands. 
  A. 
  luguhris, 
  Sowb., 
  whose 
  northern 
  limit 
  

   is 
  Todus 
  Santos 
  Bay, 
  San 
  Diego, 
  but 
  whose 
  southern 
  range 
  is 
  not 
  

   precisely 
  known, 
  though 
  it 
  reaches 
  the 
  Galapagos, 
  forms 
  a 
  connecting 
  

   link 
  between 
  the 
  northern 
  and 
  southern 
  groups.^ 
  

  

  P. 
  Fischer 
  (Manuel 
  de 
  Conchyliologie, 
  p. 
  646) 
  remarks: 
  " 
  Les 
  

   Acanthina 
  ne 
  sont 
  en 
  realite 
  q>ie 
  des 
  Purpura 
  et 
  peuvent 
  etre 
  divises 
  

   en 
  sections 
  correspondant 
  a 
  celles 
  de 
  ce 
  genre 
  par 
  leurs 
  principaux 
  

   caracteres. 
  Ij'A. 
  luffubn's, 
  Sowb., 
  est 
  un 
  TJialessa, 
  VA. 
  crassilabrum, 
  

   Lam., 
  un 
  Pohjtropa, 
  V 
  A. 
  miiricata, 
  Brod., 
  un 
  Planithais, 
  etc., 
  les 
  

   exemples 
  montrent 
  que 
  le 
  caractere 
  tire 
  de 
  la 
  presence 
  d'une 
  dent 
  au 
  

   labre 
  est 
  tout 
  a 
  fait 
  artificiel 
  et 
  sans 
  valeur." 
  

  

  There 
  is 
  much 
  to 
  be 
  said 
  in 
  favour 
  of 
  the 
  view 
  contained 
  in 
  the 
  

   last 
  sentence 
  quoted. 
  But 
  the 
  additional 
  evidence 
  drawn 
  from 
  an 
  

   examination 
  of 
  the 
  radula 
  tends 
  to 
  show 
  that 
  the 
  different 
  

   geographical 
  groups 
  of 
  Acanthma, 
  as 
  laid 
  down 
  above, 
  exhibit 
  well- 
  

   marked 
  differences 
  in 
  the 
  structure 
  of 
  this 
  organ, 
  that 
  accentuate 
  

   the 
  obvious 
  dissimilarity 
  of 
  the 
  shells. 
  Viewed 
  in 
  this 
  light 
  the 
  

   northern 
  and 
  soutliern 
  groups 
  stand 
  apart 
  from 
  one 
  another, 
  while 
  

   the 
  central 
  group, 
  or 
  what 
  remains 
  of 
  it, 
  differs 
  strongly 
  from 
  both, 
  

   if 
  it 
  does 
  not 
  disappear 
  altogether. 
  Tlie 
  affinities 
  of 
  A. 
  lugtihris, 
  

   Sowb., 
  lie 
  with 
  the 
  southern 
  group. 
  From 
  a 
  conchological 
  point 
  of 
  

   view 
  one 
  would 
  have 
  expected 
  this 
  to 
  be 
  so. 
  The 
  more 
  globular 
  

   form 
  and 
  wide 
  mouth, 
  and 
  also 
  the 
  very 
  prominent 
  tooth 
  of 
  luguhris, 
  

   bear 
  more 
  resemblance 
  to 
  the 
  forms 
  of 
  calcar 
  and 
  crassilalnim 
  than 
  to 
  

   the 
  narrow 
  long-drawn 
  shape 
  of 
  the 
  Upper 
  Californian 
  Acanthina 
  

   with 
  their 
  extremely 
  tinj^ 
  hook. 
  

  

  ^ 
  All 
  the 
  radulae 
  employed 
  in 
  the 
  preparation 
  of 
  this 
  paper 
  belong 
  to 
  the 
  

  

  collection 
  of 
  the 
  late 
  Professor 
  H. 
  M. 
  Gwatkin, 
  now 
  in 
  the 
  Natural 
  History 
  

  

  Museum, 
  South 
  Kensington. 
  

   ^ 
  Compare 
  E. 
  E. 
  C. 
  Stearns, 
  Amer. 
  Journ. 
  Conchology, 
  vii, 
  1872, 
  

  

  pp. 
  167-71; 
  W. 
  H. 
  Dall, 
  Proc. 
  U.S. 
  Mus., 
  xxxvii, 
  1909, 
  pp. 
  147-294; 
  

  

  Melvill 
  <fe 
  Standen, 
  Ann. 
  Mag. 
  Nat. 
  Hist., 
  ser. 
  vili, 
  vol. 
  xiii, 
  1914, 
  p. 
  123. 
  

  

  