﻿No. 
  1959. 
  SIPVNCULID8 
  OF 
  EASTERN 
  NORTH 
  AMERICA— 
  OEROULD. 
  423 
  

  

  The 
  size 
  of 
  the 
  larger 
  specimens, 
  extended, 
  is: 
  trunk 
  16 
  mm. 
  long 
  

   and 
  7 
  mm. 
  thick; 
  introvert 
  12 
  mm. 
  long 
  and 
  1.5 
  mm. 
  thick. 
  Still 
  

   larger 
  specimens 
  have 
  a 
  trunk 
  17 
  mm. 
  long 
  and 
  9 
  mm. 
  thick, 
  and 
  

  

  19 
  mm. 
  by 
  7 
  mm. 
  

  

  The 
  mtegument 
  of 
  the 
  posterior 
  end 
  of 
  the 
  trunk 
  in 
  some 
  specimens 
  

   is 
  so 
  thick 
  as 
  to 
  suggest 
  a 
  shield 
  like 
  that 
  of 
  Aspidosiphon, 
  but 
  this 
  

   is 
  not 
  a 
  constant 
  characteristic. 
  

  

  The 
  papillas 
  are 
  generally 
  low, 
  flat 
  domes, 
  capped 
  by 
  a 
  central 
  

   rounded 
  protuberance. 
  

  

  The 
  nerve 
  cord 
  is 
  prominent, 
  and 
  is 
  held 
  to 
  the 
  ventral 
  wall 
  of 
  

   the 
  introvert 
  by 
  a 
  

   mesentery; 
  the 
  

   lateral 
  nerves 
  are 
  

   inconspicuous. 
  A 
  

   long 
  esophagus 
  (fig. 
  

   4) 
  joins 
  an 
  intes- 
  

   tinal 
  coil 
  of 
  about 
  

  

  20 
  whorls 
  held 
  by 
  

   a 
  prominent 
  spin- 
  

   dle 
  muscle 
  at- 
  

   tached 
  posteriorly 
  

   to 
  the 
  tip 
  of 
  the 
  

   body 
  wall. 
  A 
  

   muscle 
  strand 
  ex- 
  

   tends 
  from 
  the 
  

   middle 
  of 
  the 
  

   esophagus 
  for- 
  

   ward 
  to 
  the 
  junc- 
  

   tion 
  of 
  the 
  two 
  

   ventral 
  retractors, 
  

   in 
  front 
  of 
  which 
  

   the 
  anterior 
  part 
  

   of 
  the 
  esophagus 
  is 
  

   fastened 
  to 
  the 
  re- 
  

   tractors 
  by 
  a 
  fold 
  

   of 
  peritoneum. 
  A 
  

   short, 
  simple 
  Polian 
  tube 
  or 
  contractile 
  vessel 
  lies 
  over 
  the 
  united 
  

   portion 
  of 
  the 
  pair 
  of 
  dorsal 
  retractors. 
  

  

  The 
  nephridia 
  (fig. 
  14) 
  are 
  attached 
  to 
  the 
  body 
  wall 
  nearly 
  opposite 
  

   the 
  anus. 
  They 
  are 
  of 
  medium 
  length. 
  

  

  This 
  species 
  varies 
  much 
  in 
  regard 
  to 
  the 
  position 
  of 
  the 
  points 
  of 
  

   attachment 
  of 
  the 
  retractor 
  muscles 
  to 
  the 
  body 
  wall. 
  Thus 
  in 
  one 
  

   specimen 
  both 
  pairs 
  were 
  attached 
  near 
  together 
  near 
  the 
  middle 
  of 
  

   the 
  trunk. 
  In 
  a 
  small, 
  young 
  specimen 
  the 
  ventraj 
  retractors 
  have 
  

   the 
  usual 
  attachment 
  near 
  the 
  posterior 
  end 
  of 
  the 
  body, 
  whereas 
  

  

  Fig. 
  14.— 
  Dissection 
  of 
  Physcosoma 
  capitatum. 
  X 
  4§. 
  go, 
  

   DUCTivE 
  organ; 
  771. 
  rtr. 
  d, 
  dorsal 
  retractor 
  muscle: 
  

   SPINDLE 
  muscle; 
  neph, 
  nephrxdium; 
  a. 
  esophagus. 
  

  

  REPRO- 
  

   771. 
  S-p, 
  

  

  