﻿MARINE 
  POLYCHAETE 
  WORMS 
  — 
  PETTIBONE 
  307 
  

  

  Description. 
  — 
  Length 
  18 
  mm., 
  width 
  0.5 
  mm., 
  20-21 
  setigerous 
  

   segments, 
  smgle 
  achaetous 
  antanal 
  segment 
  (may 
  appear 
  as 
  two 
  or 
  

   three 
  on 
  longer 
  ventral 
  side). 
  Prostomium 
  rounded, 
  with 
  convex 
  

   median 
  ridge 
  and 
  anteroventraUy 
  extended 
  brim. 
  First 
  three 
  setigers 
  

   with 
  one 
  or 
  two 
  acicular 
  nem"0setae; 
  with 
  some 
  long, 
  threadlike, 
  sinu- 
  

   ous 
  notosetae 
  covered 
  with 
  spinules. 
  Pygidium 
  with 
  obUque, 
  slightly 
  

   concave, 
  disclike, 
  asymmetrical 
  plate 
  (absent 
  dorsally), 
  wide 
  on 
  ven- 
  

   tral 
  side, 
  with 
  rim 
  smooth 
  or 
  slightly 
  crenulate; 
  anal 
  opening 
  terminal. 
  

  

  Remarks. 
  — 
  The 
  Point 
  Barrow 
  specimen 
  agrees 
  with 
  the 
  stem 
  form 
  

   of 
  P. 
  tenuis, 
  with 
  20 
  setigerous 
  segments 
  and 
  the 
  rim 
  of 
  the 
  pygidial 
  

   disc 
  slightly 
  crenulate 
  (in 
  var. 
  horealis 
  and 
  Jilifer 
  there 
  are 
  21 
  setigers 
  

   and 
  the 
  rim 
  of 
  the 
  pygidial 
  disc 
  is 
  smooth) 
  , 
  

  

  Nev) 
  records. 
  — 
  Arctic 
  Alaska: 
  Off 
  Point 
  Barrow 
  base, 
  16 
  miles 
  

   from 
  shore, 
  78.2 
  fms., 
  on 
  bottom 
  of 
  worm 
  tubes, 
  few 
  rocks 
  (1 
  station, 
  

   1 
  specimen). 
  Canadian 
  Arctic: 
  Ducketts 
  Cove, 
  Hurd 
  Channel, 
  

   Melville 
  Peninsula, 
  1-14 
  fms., 
  in 
  sandy 
  tubes 
  on 
  empty 
  tubes 
  of 
  

   Pectinaria, 
  Bartlett, 
  1933. 
  Greenland: 
  Small 
  bay. 
  Camp 
  No. 
  2, 
  

   Nugsuak 
  Peninsula, 
  74°7' 
  N., 
  on 
  empty 
  tubes 
  of 
  Pectinaria, 
  J. 
  C. 
  

   Martin, 
  1897. 
  

  

  Distribution. 
  — 
  Scattered 
  records 
  in 
  the 
  Arctic: 
  Alaskan 
  and 
  Cana- 
  

   dian 
  Arctic, 
  East 
  Greenland, 
  Spitsbergen, 
  Novaya 
  Zemlya. 
  Also 
  off 
  

   Cape 
  Cod, 
  Massachusetts; 
  southeastern 
  Alaska 
  to 
  British 
  Columbia; 
  

   north 
  Japan 
  Sea. 
  In 
  1-833 
  fathoms. 
  

  

  Family 
  Sabellariidae 
  

  

  Body 
  divided 
  into 
  three 
  regions: 
  (1) 
  anterior 
  thoracic 
  region 
  includ- 
  

   ing 
  two 
  anterior 
  thoracic 
  segments 
  with 
  parapodia 
  reduced 
  to 
  neuro- 
  

   podia 
  with 
  capillary 
  setae 
  and 
  two 
  large, 
  more 
  or 
  less 
  fused, 
  heavy 
  

   columns, 
  the 
  opercular 
  peduncles, 
  directed 
  anteriorly, 
  bearing 
  very 
  

   modified 
  setae 
  arranged 
  in 
  one 
  to 
  three 
  concentric 
  rows 
  and 
  forming 
  an 
  

   operculum 
  for 
  closing 
  opening 
  of 
  tube; 
  three 
  or 
  four 
  para 
  thoracic 
  

   biramous 
  segments 
  with 
  capillary 
  neurosetae 
  and 
  paddlelike 
  or 
  

   styliform 
  notosetae 
  and 
  dorsal 
  falciform 
  branchiae 
  (fig. 
  34, 
  n-q) 
  ; 
  (2) 
  

   abdominal 
  region 
  with 
  notopodia 
  in 
  form 
  of 
  broadly 
  flattened 
  pinnules 
  

   bearing 
  pectinate 
  uncini, 
  and 
  neuropodia 
  with 
  capillary 
  setae; 
  with 
  

   dorsal, 
  simple, 
  ligulate 
  or 
  falciform 
  branchiae; 
  (3) 
  caudal 
  region, 
  

   achaetous, 
  apodous, 
  cylindrical, 
  without 
  appearance 
  of 
  segmentation. 
  

   Prostomium 
  indistinct, 
  between 
  opercular 
  peduncles, 
  with 
  pair 
  of 
  

   palps 
  and 
  usually 
  a 
  median 
  tentacle. 
  Mouth 
  unarmed, 
  usually 
  sur- 
  

   rounded 
  with 
  numerous 
  filiform 
  tentacles. 
  Tube 
  of 
  sand 
  or 
  fine 
  

   gravel, 
  concreted, 
  resistant, 
  may 
  be 
  solitary 
  or 
  colonial, 
  constructing 
  

   sandy 
  reefs. 
  

  

  Represented 
  by 
  a 
  single 
  species 
  from 
  Point 
  Barrow. 
  

  

  