﻿300 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol. 
  103 
  

  

  Family 
  Arenicolidae 
  

  

  Body 
  elongate, 
  cylindrical, 
  integument 
  reticulated 
  and 
  divided 
  into 
  

   secondary 
  annuli. 
  Body 
  divided 
  into 
  two 
  or 
  three 
  distinct 
  regions: 
  

   (1) 
  anterior, 
  abranchial; 
  (2) 
  abdominal, 
  branchial, 
  each 
  segment 
  with 
  

   pair 
  of 
  dorsally-borne 
  branched 
  gills; 
  (3) 
  caudal, 
  achaetous 
  and 
  

   abranchial; 
  this 
  region 
  may 
  be 
  lacking. 
  Prostomium 
  small, 
  simple 
  

   or 
  trilobed, 
  without 
  appendages; 
  with 
  nuchal 
  groove 
  (fig. 
  34, 
  a). 
  

   Parapodia 
  biramous; 
  notopodia 
  conical, 
  setigerous, 
  with 
  spiny, 
  capU- 
  

   lary 
  setae; 
  neuropodia 
  with 
  sigmoid 
  crotchets 
  in 
  semicircular 
  tori. 
  

   Without 
  dorsal, 
  ventral, 
  and 
  anal 
  cirri. 
  Anus 
  terminal. 
  Proboscis 
  

   eversible, 
  globular, 
  papillate, 
  unarmed. 
  Constructs 
  tubes 
  or 
  burrows. 
  

  

  Represented 
  by 
  a 
  single 
  species 
  from 
  Point 
  Barrow. 
  

  

  Genus 
  Arenicola 
  Lamark, 
  1801 
  

   Arenicola 
  glacialis 
  Murdoch, 
  1884 
  

  

  Figure 
  34, 
  a 
  

  

  Arenicola 
  glacialis 
  Murdoch, 
  1884, 
  p. 
  522; 
  1885, 
  p. 
  155. 
  — 
  Ashworth, 
  1910, 
  p. 
  24, 
  

   figs. 
  10-14; 
  1912, 
  p. 
  Ill, 
  figs. 
  46, 
  47, 
  pi. 
  6; 
  1924, 
  p. 
  3, 
  fig. 
  1. 
  

  

  Description. 
  — 
  Length 
  up 
  to 
  205 
  mm., 
  width 
  11 
  mm., 
  17 
  setigerous 
  

   segments. 
  Body 
  cylindrical, 
  tapering 
  slightly 
  anteriorly 
  and 
  gradu- 
  

   ally 
  posteriorly. 
  Prostomium 
  small, 
  may 
  be 
  pretty 
  well 
  retracted 
  in 
  

   nuchal 
  groove; 
  median 
  lobe 
  small, 
  lateral 
  lobes 
  larger, 
  curved 
  (fig. 
  

   34, 
  a). 
  Body 
  divided 
  into 
  three 
  regions: 
  (1) 
  anterior 
  region 
  of 
  six 
  

   abranchial 
  setigers, 
  notopodia 
  conical 
  with 
  spiny 
  capillary 
  setae, 
  

   neuropodia 
  low 
  tori 
  with 
  few 
  sigmoid 
  crotchets; 
  (2) 
  branchial 
  region 
  

   of 
  11 
  setigers 
  each 
  divided 
  into 
  five 
  superficial 
  annuli, 
  with 
  short, 
  

   bushy, 
  arborescent 
  branchiae 
  at 
  base 
  of 
  conical 
  notopodia, 
  with 
  gill 
  

   axes 
  short, 
  branching 
  one 
  or 
  two 
  times 
  or 
  simple; 
  neuropodia 
  raised 
  

   tori 
  with 
  long 
  row 
  of 
  crotchets; 
  on 
  more 
  posterior 
  segments, 
  tori 
  

   approach 
  midventral 
  line; 
  (3) 
  caudal 
  achaetous 
  and 
  abranchial 
  region 
  

   with 
  papillae 
  feebly 
  developed, 
  without 
  processes 
  (as 
  in 
  A. 
  cristata). 
  

   Nephridial 
  pores 
  six 
  pairs, 
  on 
  setigers 
  4-9, 
  posterior 
  to 
  upper 
  part 
  of 
  

   neuropodial 
  tori. 
  Pair 
  of 
  statocysts 
  on 
  peristomium, 
  open 
  to 
  exterior. 
  

  

  Figure 
  34. 
  — 
  Arenicolidae: 
  a, 
  Arenicola 
  glacialis, 
  prostomium. 
  Maldanidae: 
  b, 
  Praxillella 
  

   praeUrmissa, 
  ventral 
  view 
  anterior 
  end; 
  c, 
  same, 
  frontal 
  view 
  cephalic 
  plate; 
  d, 
  same, 
  

   pygidial 
  funnel; 
  g, 
  same, 
  posterior 
  end; 
  /, 
  same, 
  crotchet 
  from 
  neuropodium; 
  g, 
  Maldane 
  

   sarsi, 
  lateral 
  view 
  anterior 
  end; 
  h, 
  same, 
  lateral 
  view 
  posterior 
  end; 
  i, 
  Nicomache 
  lum- 
  

   bricalis, 
  lateral 
  view 
  anterior 
  end; 
  /, 
  same, 
  lateral 
  view 
  posterior 
  end; 
  k, 
  Nicomache 
  

   per 
  sonata, 
  lateral 
  view 
  posterior 
  end; 
  /, 
  Petaloproctus 
  tenuis, 
  lateral 
  view 
  anterior 
  

   end; 
  m, 
  same, 
  lateral 
  view 
  posterior 
  end. 
  Sabellariidae: 
  n, 
  Idanthyrsus 
  armatus, 
  dorsal 
  

   view 
  anterior 
  end; 
  o, 
  same, 
  lateral 
  view 
  anterior 
  end; 
  p, 
  same, 
  palea 
  from 
  inner 
  row; 
  

   q, 
  same, 
  palea 
  from 
  outer 
  row. 
  (For 
  explanation 
  of 
  symbols, 
  see 
  p. 
  210.) 
  

  

  