﻿424 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  

  

  the 
  slender 
  dorsal 
  muscles 
  are 
  joined 
  to 
  the 
  body 
  wall 
  much 
  further 
  

   forward 
  than 
  in 
  the 
  individual 
  which 
  I 
  have 
  figured 
  (fig. 
  14), 
  and 
  

   underneath 
  the 
  nephridia. 
  In 
  general, 
  in 
  the 
  few 
  specimens 
  which 
  I 
  

   have 
  dissected, 
  the 
  position 
  of 
  the 
  attachment 
  of 
  the 
  dorsal 
  retractors 
  

   varies 
  from 
  about 
  the 
  posterior 
  end 
  of 
  the 
  first 
  third 
  of 
  the 
  trunk 
  

   backward 
  to 
  the 
  posterior 
  end 
  of 
  the 
  third 
  quarter. 
  

  

  The 
  resemblance 
  of 
  this 
  species 
  to 
  Phascolosoma 
  has 
  been 
  noted 
  

   above. 
  Like 
  Phascolosoma 
  scutigera 
  Roule 
  and 
  Ph. 
  approximatum 
  

   Roule 
  which 
  it 
  resembles 
  closely 
  in 
  its 
  proportions, 
  its 
  musculature 
  

   and 
  other 
  respects, 
  it 
  suggests 
  also 
  the 
  genus 
  Aspidosiphon, 
  though 
  

   to 
  a 
  less 
  extent 
  than 
  the 
  former 
  of 
  the 
  two 
  species 
  mentioned. 
  A 
  

   posterior 
  shield 
  is 
  distinctly 
  suggested 
  in 
  some 
  specimens 
  by 
  the 
  thick- 
  

   ening 
  of 
  the 
  mtegument 
  of 
  the 
  posterior 
  end 
  of 
  the 
  trunk 
  and, 
  to 
  a 
  less 
  

   extent, 
  at 
  the 
  anterior 
  extremity. 
  

  

  It 
  seems 
  not 
  impossible 
  that 
  some 
  of 
  the 
  deep-sea 
  sipunculids 
  

   described 
  by 
  Roule 
  (1907) 
  as 
  species 
  of 
  Phascolosoma 
  belong 
  rather 
  

   in 
  Physcosoma, 
  a 
  genus 
  which 
  Roule 
  apparently 
  does 
  not 
  recognize 
  

   as 
  including 
  several 
  species 
  originally 
  described 
  as 
  Phascolosoma 
  

   (as, 
  for 
  instance, 
  Ph. 
  agassizii 
  Keferstein, 
  Ph. 
  varians 
  Keferstein). 
  

   Thus 
  Roule's 
  Phascolosoma 
  vulgare 
  de 
  Blainville 
  var. 
  multipapillosa, 
  

   so 
  far 
  as 
  one 
  can 
  judge 
  by 
  his 
  figure 
  (fig. 
  89) 
  and 
  very 
  brief 
  description 
  

   in 
  which 
  he 
  compares 
  this 
  form 
  to 
  Phascolosoma 
  (=Physcosoma) 
  

   agassizii 
  Keferstein, 
  apparently 
  resembles 
  Physcosoma. 
  No 
  state- 
  

   ment 
  is 
  made 
  as 
  to 
  whether 
  its 
  longitudinal 
  muscle 
  layer 
  is 
  con- 
  

   tinuous, 
  as 
  in 
  Phascolosoma 
  vulgare, 
  or 
  discontinuous 
  as 
  in 
  Physcosoma 
  

   agassizii. 
  Superficially, 
  and 
  as 
  regards 
  its 
  retractor 
  muscles, 
  it 
  

   resembles 
  Physcosoma 
  capitatum. 
  The 
  one 
  individual 
  of 
  this 
  

   "variety 
  multipapillosa^^ 
  came 
  from 
  Mogador, 
  West 
  Coast 
  of 
  Africa, 
  

   and 
  a 
  depth 
  of 
  1,050 
  meters. 
  The 
  incomplete 
  crown 
  of 
  tentacles 
  in 
  

   Phascolosoma 
  ajjproximaium 
  Roule, 
  suggests 
  that 
  possibly 
  this 
  also 
  

   is 
  a 
  species 
  of 
  Physcosoma. 
  

  

  Genus 
  ASPIDOSIPHON 
  Grube. 
  

  

  Individuals 
  of 
  this 
  genus 
  have 
  a 
  distinct 
  shield 
  in 
  front 
  of 
  the 
  anus 
  

   and 
  one 
  at 
  the 
  posterior 
  extremity 
  of 
  the 
  body. 
  The 
  .introvert 
  is 
  

   much 
  slenderer 
  than 
  the 
  trunk, 
  with 
  which 
  it 
  is 
  connected 
  ventral 
  

   to 
  the 
  anal 
  shield. 
  Rings 
  of 
  hooks 
  are 
  found 
  in 
  most 
  species 
  upon 
  

   the 
  introvert. 
  The 
  longitudinal 
  muscle 
  layer 
  is 
  either 
  continuous 
  or 
  

   discontinuous. 
  Only 
  the 
  ventral 
  retractors 
  are 
  present, 
  and 
  they 
  are 
  

   fused 
  more 
  or 
  less 
  completely. 
  

  

  Most 
  of 
  the 
  species 
  of 
  Aspidosiphon 
  that 
  have 
  been 
  described 
  

   inhabit 
  the 
  Pacific 
  and 
  Indian 
  Oceans. 
  In 
  the 
  Atlantic, 
  A. 
  armatus 
  

   Koren 
  and 
  Danielssen 
  and 
  A. 
  mirahilis 
  Theel 
  occur 
  off 
  the 
  coast 
  of 
  

   Norway 
  and 
  Sweden, 
  A. 
  mulleri 
  Diesing 
  is 
  found 
  with 
  A. 
  venabulum 
  

   Selenka 
  and 
  Billow 
  off 
  the 
  west 
  coast 
  of 
  Africa 
  (Fischer, 
  1894), 
  and 
  

  

  