﻿MARINE 
  POLYCHAETE 
  WORMS 
  — 
  PETTIBONE 
  281 
  

  

  Description. 
  — 
  Up 
  to 
  50 
  mm. 
  long, 
  2.2 
  mm. 
  wide. 
  Prostomium 
  

   feebly 
  notched 
  anteriorly 
  or 
  distinctly 
  bifid, 
  prolonged 
  posteriorly 
  in 
  

   a 
  crest 
  extending 
  to 
  setiger 
  4 
  (to 
  6) 
  , 
  without 
  distinct 
  occipital 
  antenna, 
  

   with 
  fom- 
  eyes 
  in 
  trapezoidal 
  arrangement 
  (or 
  six 
  in 
  young 
  specimens) 
  

   or 
  eyes 
  lacking. 
  Palps 
  usually 
  missing 
  in 
  alcohol. 
  A 
  protrusible, 
  

   somewhat 
  lobulated, 
  brownish 
  proboscidial 
  region. 
  Branchiae 
  begin 
  

   on 
  setigers 
  7 
  or 
  8, 
  continuing 
  on 
  numerous 
  segments, 
  absent 
  from 
  

   more 
  posterior 
  segments; 
  branchiae 
  short 
  (about 
  length 
  of 
  capillary 
  

   notosetae), 
  straplike, 
  continuous 
  with 
  dorsal 
  lamellae. 
  Modified 
  seti- 
  

   ger 
  5 
  with 
  group 
  of 
  capillary 
  notosetae, 
  usually 
  5-7 
  (3-12) 
  special 
  

   amber-colored 
  hooks, 
  and 
  group 
  of 
  capillary 
  neurosetae; 
  special 
  hooks 
  

   all 
  similar, 
  falcate, 
  with 
  pectinate 
  top. 
  With 
  conspicuous, 
  somewhat 
  

   conical 
  dorsal 
  and. 
  ventral 
  postsetal 
  lamellae 
  on 
  setigers 
  1-4, 
  lacking 
  

   on 
  modified 
  setiger 
  5, 
  becoming 
  rather 
  low 
  and 
  wide 
  on 
  more 
  posterior 
  

   segments. 
  With 
  capillary 
  setae 
  in 
  both 
  notopodia 
  and 
  neuropodia; 
  

   beginning 
  on 
  setiger 
  7, 
  neuropodial 
  capillary 
  setae 
  mostly 
  replaced 
  

   by 
  hooded 
  bidentate 
  crotchets. 
  In 
  more 
  posterior 
  setigers 
  (last 
  20 
  

   or 
  so), 
  notopodia 
  conical, 
  lacking 
  branchiae 
  or 
  lamellae, 
  with 
  conical 
  

   bundle 
  of 
  awl-shaped 
  setae 
  scarcely 
  surpassing 
  notopodial 
  tip 
  and 
  

   small 
  bundle 
  of 
  capillary 
  setae; 
  neuropodia 
  with 
  two 
  or 
  three 
  crotchets 
  

   and 
  few 
  capUlary 
  setae. 
  Anal 
  disc 
  with 
  complete 
  middorsal 
  notch, 
  

   shorter 
  midventral 
  and 
  midlateral 
  notches, 
  thus 
  4-lobed. 
  Color: 
  In 
  

   alcohol: 
  Without 
  color 
  or 
  grayish. 
  

  

  Remarks. 
  — 
  The 
  type 
  of 
  P. 
  brachycephala 
  Hartman 
  from 
  central 
  

   California 
  was 
  examined 
  and 
  is 
  herein 
  referred 
  to 
  P. 
  caulleryi. 
  

  

  New 
  records. 
  — 
  Arctic 
  Alaska: 
  Off 
  Point 
  Barrow 
  base, 
  up 
  to 
  8 
  

   miles 
  from 
  shore, 
  16.7-75.5 
  fms., 
  on 
  bottoms 
  of 
  stones 
  and 
  various 
  

   combinations 
  of 
  mud, 
  gravel, 
  stones, 
  rocks, 
  large 
  perforated 
  rocks, 
  

   with 
  bryozoans 
  and 
  hydroids 
  (8 
  stations, 
  16 
  specimens). 
  West 
  Coast 
  

   North 
  America: 
  Washington 
  and 
  Puget 
  Sounds, 
  low 
  water 
  to 
  50 
  

   fms., 
  Pettibone. 
  

  

  Distribution. 
  — 
  Arctic 
  Alaska 
  to 
  central 
  California; 
  Ireland, 
  Great 
  

   Britain 
  to 
  France. 
  In 
  low 
  water 
  to 
  75.5 
  fathoms. 
  

  

  Polydora 
  larva 
  

  

  A 
  larva 
  of 
  a 
  Polydora 
  was 
  taken 
  in 
  plankton 
  August 
  2, 
  1948. 
  This 
  

   was 
  perhaps 
  the 
  larva 
  of 
  P. 
  caulleryi 
  Mesnil 
  since 
  it 
  was 
  the 
  only 
  

   species 
  of 
  Polydora 
  found 
  in 
  the 
  Point 
  Barrow 
  region. 
  Prostomium 
  

   rounded, 
  with 
  two 
  palps, 
  and 
  with 
  black 
  chroma 
  tophores. 
  Fifth 
  

   setigerous 
  segment 
  modified, 
  with 
  short, 
  thick, 
  slightly 
  curved 
  acicular 
  

   setae; 
  rest 
  of 
  21 
  setigerous 
  segments 
  with 
  long 
  larval 
  capillary 
  setae. 
  

   Pygidium 
  a 
  rounded 
  disc, 
  notched 
  middorsaUy, 
  with 
  black 
  chromato- 
  

   phores. 
  Black 
  chroma 
  tophores 
  arranged 
  transversely 
  on 
  setigers 
  2-5, 
  

   then 
  in 
  two 
  longitudinal 
  lines 
  on 
  each 
  side 
  of 
  middorsal 
  line, 
  extending 
  

   to 
  anal 
  cup. 
  

  

  