﻿416 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol.44. 
  

  

  describes 
  as 
  Ph. 
  tuhicola 
  (Verrill) 
  (=Ph. 
  strombi), 
  that 
  the 
  ventral 
  

   retractor 
  has 
  a 
  single 
  root 
  attached 
  at 
  the 
  left 
  of 
  the 
  posterior 
  end 
  

   of 
  the 
  nerve 
  cord, 
  as 
  is 
  shown 
  by 
  his 
  figure 
  82. 
  The 
  three 
  individuals 
  

   from 
  the 
  West 
  Indies 
  which 
  he 
  examined, 
  moreover, 
  lived 
  in 
  tubes 
  

   of 
  cemented 
  mud 
  and 
  sand. 
  As 
  stated 
  above, 
  I 
  have 
  found 
  this 
  

   peculiarity 
  in 
  specimens 
  from 
  the 
  shells 
  of 
  Dentalium 
  solidum, 
  so 
  that 
  

   it 
  would 
  appear 
  to 
  be 
  a 
  southern 
  characteristic 
  or 
  tendency 
  not 
  

   determined 
  by 
  the 
  nature 
  of 
  the 
  shell 
  or 
  tube 
  which 
  the 
  worm 
  inhabits, 
  

   but 
  hereditary. 
  

  

  PHASCOLION 
  ALBERTI 
  Sluiter. 
  

  

  This 
  form, 
  which 
  Sluiter 
  (1900) 
  describes, 
  apparently 
  differs 
  only 
  

   in 
  external 
  features 
  from 
  Ph. 
  strombi, 
  which 
  it 
  is 
  Uke 
  in 
  habits 
  and 
  in 
  

   the 
  arrangement 
  of 
  its 
  retractor 
  muscles. 
  The' 
  length 
  of 
  the 
  introvert 
  

   is 
  described 
  as 
  two-thirds 
  that 
  of 
  the 
  trunk, 
  in 
  which 
  respect 
  it 
  resem- 
  

   bles 
  many 
  of 
  the 
  specimens 
  of 
  Ph. 
  strombi 
  from 
  the 
  same 
  general 
  

   region 
  (vicinity 
  of 
  Nova 
  Scotia), 
  which 
  show 
  a 
  tendency 
  to 
  have 
  a 
  

   shorter 
  introvert 
  than 
  elsewhere. 
  The 
  papillae 
  of 
  the 
  anterior 
  and 
  

   middle 
  parts 
  of 
  the 
  trunk, 
  however, 
  rather 
  than 
  of 
  the 
  posterior 
  end, 
  

   bear 
  chitinous 
  denticles 
  pointing 
  forward, 
  whereas 
  those 
  near 
  the 
  

   posterior 
  extremity 
  are 
  capped 
  with 
  a 
  perforated, 
  oval 
  crown 
  of 
  

   chitinous 
  material. 
  The 
  ventral 
  nerve 
  cord 
  is 
  prolonged 
  beyond 
  the 
  

   attachment 
  of 
  the 
  ventral 
  retractors, 
  passing 
  between 
  the 
  two 
  roots. 
  

  

  This 
  form 
  was 
  taken 
  in 
  considerable 
  abundance 
  by 
  the 
  Prince 
  of 
  

   Monaco 
  at 
  his 
  station 
  161, 
  off 
  Newfoundland, 
  lat. 
  46° 
  04' 
  40'' 
  N.; 
  

   long. 
  49° 
  02' 
  30" 
  W., 
  m 
  1,267 
  meters, 
  and 
  off 
  Cape 
  Finisterre 
  in 
  

   1,674 
  meters. 
  It 
  has 
  not 
  been 
  found, 
  to 
  my 
  knowledge, 
  by 
  any 
  

   expedition 
  from 
  the 
  United 
  States 
  that 
  has 
  explored 
  the 
  same 
  general 
  

   region. 
  

  

  Genus 
  DENDROSTOMA 
  Grube. 
  

  

  This 
  genus 
  includes 
  a 
  few 
  species 
  which 
  are 
  distinguished 
  from 
  their 
  

   natural 
  allies 
  of 
  the 
  genus 
  Phascolosoma 
  by 
  the 
  tree-like 
  branching 
  of 
  

   their 
  tentacles, 
  which 
  are 
  ramifications 
  of 
  from 
  four 
  to 
  eight 
  main 
  

   trunks. 
  The 
  longitudinal 
  muscle 
  layer 
  is 
  continuous, 
  the 
  nephridia 
  

   free, 
  and 
  the 
  mtestinal 
  coil 
  unattached 
  behind. 
  The 
  tnmk 
  in 
  most 
  

   species 
  is 
  short 
  and 
  thick. 
  The 
  short 
  introvert 
  is 
  provided 
  with 
  hooks 
  

   or 
  spines, 
  except 
  in 
  D. 
  peruvianum 
  Collin. 
  The 
  PoHan 
  vessel 
  (con- 
  

   tractile 
  tube) 
  is 
  provided 
  in 
  most 
  cases, 
  though 
  not 
  in 
  D. 
  blandum 
  

   Selenka 
  and 
  De 
  Man, 
  with 
  numerous 
  caeca. 
  These 
  species 
  inhabit 
  

   tropical 
  seas. 
  

  

  Of 
  the 
  six 
  recorded 
  species 
  D. 
  pinnifolium 
  Keferstein 
  has 
  four 
  

   retractor 
  muscles, 
  the 
  others 
  have 
  two. 
  D. 
  pinnifolium 
  Keferstein, 
  

   as 
  well 
  as 
  D. 
  alutaceum 
  Grube, 
  is 
  found 
  in 
  the 
  West 
  Indies 
  (St. 
  Thomas, 
  

   Selenka); 
  D. 
  peruvianum 
  Collin 
  off 
  the 
  Peruvian 
  coast; 
  D. 
  blandum 
  

   Selenka 
  and 
  De 
  Man, 
  D. 
  signifer 
  Selenka 
  and 
  De 
  Man, 
  and 
  D.spinifer 
  

   Sluiter 
  in 
  the 
  western 
  part 
  of 
  the 
  Pacific 
  Ocean. 
  

  

  