﻿374 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol.44. 
  

  

  tuhicola 
  of 
  Verrill 
  is 
  one 
  of 
  seven 
  recognizable 
  varieties, 
  which 
  are 
  

   described 
  in 
  detail 
  in 
  this 
  paper. 
  

  

  The 
  genus 
  AspidosipTion, 
  which 
  hitherto 
  has 
  not 
  been 
  described 
  as 
  

   occurring 
  off 
  the 
  Atlantic 
  coast 
  of 
  North 
  America, 
  is 
  found 
  to 
  be 
  

   represented 
  here 
  by 
  two 
  new 
  species. 
  A 
  new 
  deep-sea 
  species 
  is 
  added 
  

   to 
  the 
  genus 
  Physcosoma 
  ( 
  = 
  Phymosoma), 
  remarkable 
  for 
  the 
  con- 
  

   tinuity 
  of 
  its 
  longitudinal 
  musculature. 
  The 
  range 
  of 
  Dendrostoma 
  

   alutaceum, 
  which 
  has 
  been 
  known 
  as 
  a 
  West 
  Indian 
  form, 
  proves 
  to 
  

   extend 
  northward 
  to 
  Cape 
  Hatteras. 
  Sipunculus 
  is 
  found 
  to 
  be 
  

   represented 
  not 
  only 
  by 
  the 
  cosmopolitan 
  S. 
  nudus, 
  well 
  known 
  to 
  

   occur 
  off 
  the 
  coasts 
  of 
  North 
  Carolina 
  and 
  Florida, 
  but 
  also 
  by 
  

   S. 
  priapuloides 
  Koren 
  and 
  Danielssen, 
  a 
  deep-sea 
  species, 
  the 
  range 
  

   of 
  which 
  off 
  the 
  American 
  coast 
  extends 
  from 
  the 
  latitude 
  of 
  

   Charleston, 
  South 
  Carolina, 
  northward 
  to 
  that 
  of 
  New 
  York 
  City. 
  

   Siphonosoma 
  cumanense 
  (Keferstein) 
  ( 
  = 
  PJiascolosoma 
  cumanense 
  = 
  

   Sipunculus 
  cumanensis) 
  , 
  an 
  interesting 
  example 
  of 
  Spengel's 
  new 
  

   genus 
  Siphonosoma, 
  hitherto 
  recorded 
  from 
  the 
  coast 
  of 
  Venezuela 
  

   and 
  the 
  West 
  Indies, 
  is 
  found 
  to 
  occur 
  also 
  in 
  Florida. 
  

  

  It 
  may 
  be 
  inferred 
  from 
  the 
  large 
  amount 
  of 
  sipunculid 
  material 
  

   in 
  the 
  National 
  Museum 
  from 
  numerous 
  northern 
  stations 
  that 
  the 
  

   collection 
  is 
  fairly 
  representative 
  of 
  the 
  fauna 
  of 
  this 
  group 
  within 
  

   the 
  area 
  extending 
  from 
  Labrador 
  to 
  Cape 
  Hatteras. 
  The 
  sub- 
  

   tropical 
  region 
  southward 
  from 
  the 
  latter 
  j^oint, 
  however, 
  has 
  been 
  

   less 
  thoroughly 
  explored, 
  though 
  southern 
  Florida, 
  at 
  least, 
  is 
  known 
  

   to 
  be 
  inhabited 
  by 
  many 
  interesting 
  forms. 
  

  

  ; 
  It 
  is 
  the 
  purpose 
  of 
  this 
  paper 
  to 
  make 
  this 
  fauna 
  available 
  to 
  biol- 
  

   ogists 
  by 
  presenting 
  such 
  descriptions 
  of 
  external 
  features 
  and 
  inter- 
  

   nal 
  structure 
  as 
  are 
  necessary 
  for 
  the 
  easy 
  determination 
  of 
  species, 
  

   by 
  pointing 
  out 
  the 
  variability 
  of 
  certain 
  plastic 
  forms 
  that 
  are 
  

   suitable 
  for 
  experimental 
  work, 
  and 
  by 
  bringing 
  together 
  what 
  is 
  

   known 
  about 
  the 
  geographical 
  distribution 
  of 
  the 
  group 
  between 
  

   Labrador 
  and 
  Key 
  West. 
  Since 
  the 
  material 
  at 
  hand 
  ^vill 
  not 
  permit 
  

   of 
  an 
  account 
  of 
  the 
  sipunculids 
  of 
  the 
  West 
  Indian 
  and 
  South 
  Amer- 
  

   ican 
  region 
  that 
  would 
  be 
  at 
  all 
  complete, 
  I 
  shall 
  here 
  describe 
  sucli 
  

   subtropical 
  and 
  tropical 
  forms 
  only 
  as 
  have 
  been 
  found 
  along 
  tlic 
  

   coast 
  of 
  Florida. 
  

  

  It 
  would 
  be 
  a 
  profitable 
  study, 
  however, 
  if 
  sufficient 
  material 
  were 
  

   available, 
  to 
  compare 
  with 
  one 
  another 
  the 
  sipunculids 
  of 
  the 
  two 
  

   sides 
  of 
  the 
  Isthmus 
  of 
  Panama. 
  Physcosoma 
  agassizii 
  (Keferstein), 
  

   ' 
  Aspidosiphon 
  truncatus 
  Keferstein, 
  and 
  Dendrostoma 
  peruvianum 
  Col- 
  

   lin, 
  have 
  been 
  found, 
  so 
  far 
  as 
  I 
  know, 
  only 
  in 
  the 
  Pacific, 
  while 
  

   'Physcosoma 
  pectinatum 
  (Keferstein) 
  and 
  Ph. 
  antiUarum 
  (Grube 
  and 
  

   Orsted), 
  Sipunculus 
  nudus, 
  and 
  S. 
  tituhans 
  Selenka 
  and 
  Biilow 
  occur 
  

   on 
  both 
  sides 
  of 
  the 
  Isthmus. 
  The 
  exclusively 
  Atlantic 
  subtropical 
  

   species 
  inhabiting 
  the 
  region 
  southward 
  from 
  Cape 
  Hatteras 
  through 
  

  

  