﻿ANATOMY 
  AND 
  AFFINITIES 
  OF 
  THE 
  TEOCHIP^l. 
  37 
  

  

  are 
  branched 
  at 
  their 
  extremities, 
  thus 
  presenting 
  an 
  appear- 
  

   ance 
  simihir 
  to 
  that 
  described 
  by 
  Woodward 
  in 
  the 
  ceplialic 
  

   tentacles 
  of 
  Pleurotomaria 
  (45, 
  pi. 
  13, 
  fig. 
  1). 
  In 
  none 
  

   of 
  the 
  adult 
  specimens 
  of 
  Trochus 
  examined 
  have 
  I 
  noticed 
  

   an 
  indication 
  of 
  thisbi-anching, 
  even 
  as 
  an 
  abnormality, 
  though 
  

   one 
  specimen 
  of 
  T. 
  zizy 
  phinus 
  exhibited 
  a 
  most 
  peculiar 
  and 
  

   interesting 
  abnoi-mality, 
  in 
  that 
  on 
  tlie 
  right 
  ocular 
  peduncle 
  

   three 
  eyes 
  were 
  present 
  in 
  place 
  of 
  the 
  usual 
  one. 
  The 
  left 
  

   eye 
  was 
  i^erfectly 
  normal.^ 
  

  

  The 
  third 
  pair 
  of 
  ajipendages 
  present 
  on 
  the 
  head 
  of 
  the 
  

   TrochidtB 
  are 
  the 
  cephalic 
  lappets 
  (figs. 
  5, 
  6, 
  7, 
  c. 
  I.) 
  These 
  

   structures 
  are 
  very 
  varial)le 
  in 
  size 
  : 
  in 
  those 
  species 
  belonging 
  

   to 
  the 
  sub-genus 
  Clibbula 
  they 
  are 
  large 
  and 
  conspicuous, 
  

   their 
  free 
  margins 
  ])eing 
  fringed 
  and 
  ciliated; 
  whilst 
  in 
  

   T. 
  zizyphiiius 
  and 
  other 
  species 
  belonging 
  to 
  the 
  sub-genus 
  

   Calliostoma 
  they 
  are 
  exti^emely 
  small 
  and 
  sometimes 
  entirely 
  

   absent. 
  In 
  connection 
  with 
  the 
  ocular 
  peduncles 
  thei'e 
  is 
  a 
  

   most 
  remarkable 
  little 
  organ 
  existing 
  in 
  many 
  of 
  the 
  species 
  

   of 
  Troch 
  us, 
  viz. 
  a 
  small 
  pointed 
  a.ppendix 
  situated 
  underneath 
  

   and 
  behind 
  tiie 
  right 
  ocular 
  peduncle 
  (fig. 
  5, 
  a. 
  oc. 
  ^;».) 
  In 
  

   T. 
  cinerarius 
  (Pelseneer, 
  36, 
  pp. 
  46, 
  47) 
  and 
  T. 
  unibilicatus 
  

   it 
  is 
  comparatively 
  large, 
  and 
  can 
  easily 
  be 
  found. 
  It 
  is 
  

   present 
  in 
  T. 
  magus 
  and 
  T.lineatus, 
  though 
  much 
  smaller 
  

   than 
  in 
  the 
  preceding 
  species, 
  and 
  is 
  noticeable 
  only 
  as 
  a 
  

   small 
  protuberance 
  on 
  the 
  ocular 
  peduncle. 
  Clarke 
  (11, 
  

   p. 
  313) 
  has 
  described 
  a 
  similar 
  appendix 
  in 
  T. 
  tumid 
  us 
  as 
  a 
  

   penis, 
  though 
  in 
  the 
  three 
  specimens 
  of 
  this 
  species 
  which 
  I 
  

   examined 
  I 
  was 
  unable 
  to 
  find 
  any 
  trace 
  of 
  the 
  structure. 
  In 
  

   the 
  sub-genus 
  Calliostoma 
  it 
  is 
  variable 
  in 
  its 
  appearance 
  

   or 
  non-a]ipeara7ice 
  : 
  T. 
  zizypliinus 
  and 
  T. 
  granulatus 
  

   are 
  entirely 
  without 
  it, 
  while 
  in 
  T. 
  striatus 
  and 
  T. 
  ex- 
  

   asperatus, 
  though 
  small, 
  it 
  is 
  usually 
  present. 
  It 
  is 
  not 
  

   confined 
  to 
  the 
  Trochidte, 
  but 
  is 
  present 
  in 
  other 
  genera, 
  viz. 
  

   Crepidula, 
  Capulus, 
  and 
  Calyptrea, 
  being 
  especially 
  

   well 
  developed 
  in 
  the 
  last 
  genus. 
  It 
  has 
  been 
  regarded 
  by 
  

   several 
  observers 
  as 
  being 
  of 
  the 
  nature 
  of 
  a 
  penis, 
  but 
  in 
  

   1 
  Vide 
  'Nature; 
  No. 
  1093, 
  vol. 
  Ixv, 
  p. 
  535, 
  April 
  lOtJi, 
  1902. 
  

  

  