﻿MARINE 
  POLYCHAETE 
  WORMS 
  — 
  PETTIBONE 
  311 
  

  

  not 
  retractile 
  in 
  mouth; 
  dorsal 
  and 
  posterior 
  to 
  paleae 
  a 
  semilunar 
  

   flat 
  or 
  concave 
  cephalic 
  plate 
  limited 
  posteriorly 
  by 
  an 
  entire 
  or 
  

   crenulate 
  rim; 
  two 
  pairs 
  tentacular 
  cirri 
  with 
  first 
  pair 
  lateral 
  to 
  base 
  

   of 
  paleae, 
  second 
  pair 
  lateral 
  to 
  rim 
  of 
  cephalic 
  plate 
  (fig. 
  35, 
  c, 
  d). 
  

   Body 
  divided 
  into 
  three 
  regions: 
  (1) 
  anterior 
  thoracic, 
  including 
  two 
  

   achaetous 
  segments 
  each 
  with 
  a 
  pair 
  of 
  lateral 
  pectinate 
  branchiae, 
  

   three 
  notopodial 
  uniramous 
  setigers 
  lacking 
  neuropodia; 
  ventral 
  side 
  

   anterior 
  region 
  with 
  thick 
  glandular 
  cushions 
  ; 
  (2) 
  median 
  abdominal, 
  

   with 
  biramous 
  segments 
  (except 
  last 
  few 
  may 
  have 
  notosetae 
  only), 
  

   notopodia 
  with 
  setae 
  capillary, 
  limbate, 
  smooth 
  or 
  finely 
  den 
  tided; 
  

   neuropodia 
  in 
  form 
  of 
  wide 
  pinnules 
  bearing 
  single 
  row 
  of 
  pectiniform 
  

   uncini; 
  (3) 
  posterior 
  anal 
  plaque 
  or 
  scapha, 
  small, 
  foliaceous, 
  concave 
  

   dorsally, 
  folded 
  under 
  abdomen, 
  with 
  rudimentary 
  achaetous 
  segments 
  

   except 
  for 
  the 
  first 
  segment 
  which 
  has 
  a 
  series 
  of 
  acicular, 
  more 
  or 
  

   less 
  recurved 
  setae 
  (the 
  scaphal 
  hooks); 
  an 
  oval 
  or 
  filiform 
  ligule 
  

   above 
  the 
  anus 
  (fig. 
  35, 
  g, 
  h). 
  Tube 
  free, 
  conical, 
  rigid, 
  fragile, 
  open 
  

   at 
  both 
  ends, 
  straight 
  or 
  arcuate, 
  formed 
  of 
  a 
  single 
  layer 
  of 
  cemented 
  

   sand 
  grains 
  or 
  shells, 
  and 
  liued 
  by 
  a 
  membrane. 
  Live 
  in 
  sand 
  or 
  mud, 
  

   with 
  anterior 
  and 
  larger 
  end 
  of 
  tube 
  directed 
  below. 
  May 
  secrete 
  

   mucus 
  in 
  abundance. 
  

  

  Represented 
  by 
  a 
  single 
  genus 
  (and 
  subgenus) 
  and 
  two 
  species 
  

   from 
  Point 
  Barrow. 
  

  

  Genus 
  Pectinaria 
  Laxnark, 
  1818 
  

  

  Subgenus 
  Cistenides 
  Malmgren, 
  1865 
  

  

  Both 
  species 
  have 
  the 
  tube 
  sHghtly 
  arched, 
  lined 
  with 
  rusty- 
  

   colored 
  membrane. 
  Tentacular 
  membrane 
  free, 
  the 
  lateral 
  portions 
  

   not 
  fused 
  to 
  paleal 
  segment, 
  with 
  30-45 
  filiform 
  to 
  clavate 
  marginal 
  

   papillae. 
  Oral 
  tentacles 
  short, 
  thick, 
  grooved. 
  Dorsal 
  rim 
  of 
  flat 
  

   paleal 
  segment 
  entire, 
  not 
  den 
  tided 
  (fig. 
  35, 
  d). 
  Usually 
  17 
  segments 
  

   with 
  capillary 
  notosetae 
  (15-17, 
  the 
  last 
  two 
  segments 
  may 
  have 
  the 
  

   notosetae 
  few 
  in 
  number 
  or 
  lacking), 
  of 
  which 
  12 
  (beginning 
  on 
  setiger 
  

   4) 
  have 
  elongate 
  flattened 
  pinnules 
  bearing 
  single 
  rows 
  of 
  neuropodial 
  

   uncini; 
  pectiniform 
  uncini 
  thin, 
  flat, 
  with 
  3-4 
  major 
  teeth 
  and 
  4-5 
  

   small 
  ones 
  above 
  basal 
  process 
  (fig. 
  35, 
  /). 
  Anal 
  plaque 
  distinctly 
  

   separated 
  from 
  abdomen 
  by 
  constriction, 
  suboval, 
  festooned 
  laterally 
  

   (rudimxcntary 
  parapodia) 
  ; 
  basally 
  with 
  7-1 
  1 
  pairs 
  short, 
  heavy 
  scaphal 
  

   hooks 
  (fig. 
  35, 
  g). 
  

  

  Key 
  to 
  the 
  species 
  of 
  Pectinaria 
  (Cistenides) 
  from 
  Point 
  Barrow 
  

  

  1. 
  Cephalic 
  paleae 
  usually 
  7-9 
  pairs 
  (7-13), 
  heavy, 
  with 
  blunt 
  tips 
  (or 
  very 
  short 
  

  

  sharp 
  tips; 
  fig. 
  35, 
  i, 
  f) 
  P. 
  (C.) 
  granulata 
  

  

  Cephalic 
  paleae 
  usually 
  11-14 
  pairs 
  (9-15), 
  long, 
  tapered 
  to 
  slender 
  pointed 
  

   tips 
  (fig. 
  35, 
  e) 
  P. 
  (C.) 
  hyperborea 
  

  

  