﻿308 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  voi^ 
  m 
  

  

  Genus 
  Idanthyrsus 
  Kinberg, 
  1867 
  

   Idanthyrsus 
  armatus 
  Eauberg, 
  1867 
  

  

  Figure 
  34, 
  n-q 
  

  

  Idanthyrsus 
  armatus 
  Kinberg, 
  1867, 
  p. 
  350. 
  — 
  Johansson, 
  1926, 
  p. 
  9; 
  1927, 
  p. 
  90. 
  — 
  

   Monro, 
  1930, 
  p. 
  117, 
  fig. 
  73; 
  1936, 
  p. 
  172.— 
  Annenkova, 
  1937, 
  p. 
  184; 
  1938, 
  

   p. 
  196.— 
  Okuda, 
  1938a, 
  p. 
  242, 
  figs. 
  4, 
  5.— 
  Hartman, 
  1944c, 
  p. 
  336, 
  pi. 
  31, 
  

   fig. 
  36.— 
  Berkeley 
  and 
  Berkeley, 
  1952, 
  p. 
  107, 
  figs. 
  220-222. 
  

  

  Idanthyrsus 
  ornamentatus 
  Chamberlin, 
  1919, 
  p. 
  262, 
  pi. 
  3, 
  figs. 
  2-5. 
  — 
  Hartman, 
  

   1944c, 
  p. 
  337, 
  pi. 
  31, 
  fig. 
  34; 
  1948, 
  p. 
  43.— 
  Hartman 
  and 
  Reish, 
  1950, 
  p. 
  41. 
  

  

  Description. 
  — 
  Length 
  up 
  to 
  60 
  mm., 
  width 
  5 
  mm., 
  caudal 
  lobe 
  11 
  

   mm. 
  Body 
  widest 
  anteriorly, 
  tapering 
  gradually 
  posteriorly, 
  with 
  

   achaetous 
  caudal 
  region 
  sharply 
  set 
  off 
  from 
  body. 
  Opercular 
  pe- 
  

   duncles 
  elongated, 
  semicyUndrical, 
  completely 
  separated 
  and 
  diver- 
  

   gent 
  anteriorly, 
  obliquely 
  truncated 
  distally, 
  with 
  two 
  rows 
  modified 
  

   golden 
  setae 
  or 
  paleae; 
  inner 
  row 
  paleae 
  rather 
  stout, 
  smooth, 
  gently 
  

   curved, 
  tapering 
  gradually 
  to 
  acute 
  tips, 
  7-16 
  per 
  column; 
  outer 
  row 
  

   paleae 
  more 
  slender, 
  straight 
  or 
  slightly 
  curved, 
  with 
  coarse 
  lateral 
  

   spines, 
  16-36 
  per 
  column; 
  row 
  of 
  9-15 
  distal 
  papillae 
  per 
  column, 
  at 
  

   base 
  of 
  outer 
  paleae. 
  One 
  or 
  two 
  pairs 
  heavy, 
  deep 
  amber-colored, 
  

   strongly-bent 
  nuchal 
  hooks 
  on 
  dorsal 
  side 
  opercular 
  peduncles. 
  

   Numerous 
  filiform 
  oral 
  tentacles 
  on 
  ventral 
  side 
  opercular 
  peduncles. 
  

   Pair 
  of 
  grooved 
  slender 
  palps 
  and 
  median 
  tentacle 
  between 
  bases 
  of 
  

   peduncles. 
  First 
  thoracic 
  segment 
  short, 
  with 
  ventral 
  group 
  capiUary 
  

   setae 
  lateral 
  to 
  conical 
  papilla. 
  Second 
  segment 
  with 
  lateral 
  group 
  

   capillary 
  setae, 
  three 
  papillae 
  and 
  dorsal 
  branchiae. 
  Three 
  para- 
  

   thoracic 
  segments 
  with 
  rectangular 
  palletlike 
  pinnules 
  with 
  flattened, 
  

   paddlelike 
  ilotosetae; 
  neurosetae 
  bipinnate 
  capillary 
  setae. 
  Abdom- 
  

   inal 
  segments 
  with 
  wide, 
  flattened 
  dorsal 
  pinnules 
  bearing 
  pectinate 
  

   uncini; 
  capillary 
  barbed 
  neurosetae. 
  Caudal 
  lobe 
  smooth, 
  achaetous. 
  

   Paired 
  dorsal 
  branchiae 
  cirriform, 
  with 
  transverse 
  ridges 
  on 
  medial 
  

   side, 
  begin 
  on 
  setiger 
  2, 
  absent 
  on 
  last 
  few 
  abdominal 
  segments. 
  

   Color: 
  In 
  life: 
  Reddish 
  brown 
  to 
  dark 
  violet 
  anteriorly, 
  branchiae 
  

   red, 
  paleae 
  golden 
  yellow. 
  In 
  alcohol: 
  Colorless, 
  with 
  purple 
  

   patches 
  anteriorly. 
  Tube: 
  Thick, 
  of 
  coarse 
  sand 
  grains 
  neatly 
  ce- 
  

   mented 
  together, 
  very 
  resistant, 
  one 
  side 
  flattened, 
  attached 
  to 
  rocks, 
  

   shells, 
  crustaceans; 
  upper 
  surface 
  convex. 
  

  

  Remarks. 
  — 
  /. 
  ornamentatus 
  Chamberlin 
  is 
  herein 
  referred 
  to 
  /. 
  

   armatus, 
  following 
  Okuda 
  (1938). 
  According 
  to 
  observations 
  by 
  G. 
  

   E. 
  MacGinitie 
  it 
  is 
  a 
  hardy 
  species, 
  a 
  specimen 
  living 
  in 
  a 
  pail 
  in 
  the 
  

   laboratory 
  for 
  three 
  days, 
  on 
  a 
  rock 
  covered 
  with 
  a 
  mass 
  of 
  barnacles, 
  

   etc. 
  Male 
  specimen, 
  collected 
  from 
  70 
  fathoms, 
  spawned 
  in 
  the 
  

   laboratory 
  August 
  9, 
  1949. 
  

  

  