﻿MARINE 
  POLYCHAETE 
  WORMS 
  — 
  PETTIBONE 
  321 
  

  

  Branchiae 
  2-3 
  pairs, 
  single, 
  filiform 
  (fig. 
  37, 
  g). 
  Notosetae 
  and 
  uncini 
  

   (crotchets) 
  both 
  begin 
  on 
  segment 
  6. 
  Tentacular 
  lobe 
  folded, 
  with 
  very- 
  

   numerous 
  thin, 
  cylindrical, 
  and 
  short, 
  grooved 
  tentacles, 
  

  

  Trichobranchus 
  (p. 
  329) 
  

  

  Branchiae 
  single, 
  consisting 
  of 
  large 
  cylindrical 
  trunk 
  and 
  4 
  pectinate 
  lobes 
  

   (fig. 
  37, 
  j). 
  Notosetae 
  begin 
  on 
  segment 
  3, 
  uncini 
  begin 
  on 
  segment 
  8 
  

   (setiger 
  6). 
  Tentacular 
  lobe 
  large, 
  folded, 
  with 
  numerous 
  tentacles 
  of 
  a 
  

   single 
  kind 
  Terebellides 
  (p. 
  330) 
  

  

  Genus 
  Amphitrite 
  O. 
  F. 
  Muller, 
  1771 
  

  

  Both 
  species 
  have 
  the 
  body 
  inflated 
  anteriorly, 
  decidedly 
  atten- 
  

   uated 
  posteriorly. 
  Cephalic 
  ridge 
  without 
  eye-spots. 
  Branchiae 
  

   three 
  pairs, 
  on 
  segments 
  2-4. 
  Notosetae 
  begin 
  on 
  segment 
  4; 
  uncini 
  

   begin 
  on 
  segment 
  5, 
  in 
  single 
  rows 
  on 
  first 
  six, 
  in 
  double 
  rows 
  on 
  rest 
  

   of 
  thoracic 
  setigers, 
  in 
  single 
  rows 
  on 
  abdominal 
  segments 
  on 
  project- 
  

   ing 
  pinnules. 
  Pygidium 
  a 
  crenulate 
  ring. 
  

  

  Key 
  to 
  the 
  species 
  of 
  Amphitrite 
  from 
  Point 
  Barrow 
  

  

  1. 
  Branchiae 
  cirriform, 
  a 
  tuft 
  of 
  simple 
  filaments 
  from 
  short, 
  sUghtly 
  swollen 
  

  

  common 
  base 
  (fig. 
  36, 
  g). 
  Thoracic 
  setigers 
  17 
  A. 
  cirrata 
  

  

  Branchiae 
  branched. 
  Thoracic 
  setigers 
  19 
  A. 
  groenlandica 
  

  

  Amphitrite 
  cirrata 
  Muller, 
  1776 
  

  

  Figure 
  36, 
  g, 
  h 
  

  

  Amphitrite 
  cirrata 
  O. 
  F. 
  Mtiller, 
  1776, 
  p. 
  216.— 
  Malmgren, 
  1865, 
  p. 
  375, 
  pi. 
  21, 
  

   fig. 
  53.— 
  Webster 
  and 
  Benedict, 
  1887, 
  p. 
  748.— 
  Hessle, 
  1917, 
  p. 
  185.— 
  

   Chamberhn, 
  1920, 
  p. 
  22.— 
  Eliason, 
  1920, 
  p. 
  74.— 
  Fauvel, 
  1927, 
  p. 
  251, 
  

   fig. 
  86, 
  i-o.— 
  Augener, 
  1928, 
  p. 
  785.— 
  Okuda, 
  1938b, 
  p. 
  102.— 
  Hartman, 
  

   1944a, 
  pp. 
  334, 
  342; 
  1948, 
  p. 
  43.— 
  Thorson, 
  1946, 
  p. 
  127, 
  figs. 
  71, 
  72.— 
  

   Gorbunov, 
  1946, 
  p. 
  39.— 
  Zatsepin, 
  1948, 
  p. 
  156, 
  pi. 
  38, 
  fig. 
  12.— 
  Wesenberg- 
  

   Lund, 
  1950a, 
  p. 
  50; 
  1950b, 
  p. 
  116; 
  1951, 
  p. 
  106.— 
  Berkeley 
  and 
  Berkeley, 
  

   1952, 
  p. 
  86, 
  fig. 
  175. 
  

  

  Amphitrite 
  radiata 
  Moore, 
  1908, 
  p. 
  350; 
  1923, 
  p. 
  193. 
  

  

  Description. 
  — 
  Length 
  up 
  to 
  200 
  mm., 
  width 
  10 
  mm. 
  About 
  12 
  

   ventral 
  shields. 
  Branchiae 
  3 
  pairs, 
  cirriform, 
  a 
  tuft 
  of 
  simple 
  fila- 
  

   ments 
  from 
  a 
  short 
  common 
  base. 
  Each 
  of 
  thi-ee 
  branchial 
  segments 
  

   (segments 
  2-4) 
  with 
  pair 
  of 
  lateral 
  lobes. 
  Nephridial 
  papillae 
  7 
  

   pairs; 
  on 
  segment 
  3, 
  prominent 
  papillae 
  ventral 
  to 
  second 
  branchial 
  

   pair; 
  on 
  segments 
  6-11, 
  rather 
  inconspicuous 
  papillae 
  between 
  noto- 
  

   podia 
  and 
  neuropodia. 
  Thoracic 
  setigers 
  17. 
  Color: 
  In 
  alcohol: 
  

   Keddish 
  brown. 
  Tube: 
  Mostly 
  of 
  mud, 
  with 
  scattered 
  small 
  pebbles 
  

   and 
  debris, 
  soft, 
  breaking 
  easily. 
  

  

  New 
  records. 
  — 
  Arctic 
  Alaska: 
  Eluitkak 
  Pass, 
  Elson 
  Lagoon; 
  off 
  

   Point 
  Barrow 
  base, 
  up 
  to 
  7 
  miles 
  from 
  shore, 
  18.3-70 
  fms., 
  on 
  various 
  

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

   rocks, 
  shells 
  (8 
  stations, 
  14 
  specimens). 
  West 
  Coast 
  North 
  

  

  