﻿ECHIUROID 
  WORMS 
  OF 
  NORTH 
  PACIFIC 
  — 
  FISHER 
  221 
  

  

  Family 
  ECHIURIDAE 
  (de 
  Blainville, 
  1827, 
  restricted) 
  

  

  KEY 
  TO 
  GENERA 
  

  

  a'. 
  Two 
  circles 
  of 
  posterior 
  setae 
  Echiurus 
  Gu6rin-M6ncville 
  (p. 
  225) 
  

  

  a*. 
  No 
  posterior 
  setae 
  present. 
  

  

  b^. 
  Proboscis 
  absent 
  Arhynchite 
  Sjito 
  (p. 
  247) 
  

  

  6*. 
  Proboscis 
  present. 
  

  

  c*. 
  No 
  differentiated 
  thicker 
  bands 
  in 
  longitudinal 
  muscle 
  layer, 
  

   d*. 
  Nephrostome 
  of 
  nephridia 
  without 
  elongated, 
  si)irally 
  coiled 
  lips. 
  

  

  Thalassema 
  Lamarck 
  (p. 
  230) 
  

   (P. 
  Nephrostome 
  with 
  elongated, 
  spirally 
  coiled 
  lii)s. 
  

  

  Anelassorhjmchus 
  Annandale 
  (p. 
  221) 
  

  

  c*. 
  Longitudinal 
  muscle 
  layer 
  with 
  very 
  slight 
  to 
  pronounced 
  differentiation 
  

  

  into 
  longitudinal 
  bands, 
  8 
  or 
  more 
  in 
  number. 
  

  

  d'. 
  Nephrostome 
  of 
  nei)hridia 
  without 
  spirally 
  coiled 
  lips; 
  inner 
  layer 
  of 
  

  

  muscles 
  not 
  differentiated 
  into 
  separate 
  transverse 
  fascicles 
  between 
  

  

  longitudinal 
  bands 
  Lissomyema, 
  new 
  genus 
  (p. 
  224) 
  

  

  (P. 
  Nephrostome 
  with 
  elongated 
  spiral 
  lips. 
  

  

  e'. 
  Differentiated 
  longitudinal 
  muscle 
  bands 
  weak, 
  zones 
  between 
  not 
  

   showing 
  a 
  fasciculate 
  arrangement 
  of 
  inner 
  oblique 
  muscles; 
  in 
  

   small 
  specimens 
  longitudinal 
  bands 
  very 
  faint 
  or 
  visible 
  only 
  in 
  

  

  posterior 
  region 
  Listriolobus 
  W. 
  Fischer 
  (p. 
  233) 
  

  

  e'. 
  Longitudinal 
  muscle 
  bands 
  strongly 
  developed, 
  zones 
  between 
  

   crossed 
  by 
  separated 
  fascicles 
  of 
  innermost, 
  oblique 
  layer. 
  

   p. 
  Nephridia 
  in 
  1 
  to 
  5 
  pairs; 
  vascular 
  ring 
  vessel 
  at 
  beginning 
  of 
  

  

  midgut 
  Ochetostoma 
  Lcuckart 
  and 
  Ruppell 
  (p. 
  240) 
  

  

  p. 
  Nephridia, 
  at 
  least 
  in 
  male, 
  in 
  to 
  14 
  groups 
  of 
  1 
  to 
  4, 
  the 
  groups 
  

   arranged 
  in 
  pairs; 
  vascular 
  ring 
  vessel 
  at 
  posterior 
  end 
  of 
  

   pharynx 
  Ikedosoma 
  Bock 
  (p. 
  224) 
  

  

  Remarks. 
  — 
  In 
  the 
  foregoing 
  synopsis 
  all 
  the 
  generic 
  divisions, 
  

   with 
  the 
  exception 
  of 
  Echiurus, 
  are 
  the 
  result 
  of 
  subdividing 
  the 
  old 
  

   genus 
  Thalassema. 
  In 
  a 
  very 
  real 
  sense 
  these 
  groups 
  are 
  provisional 
  

   because 
  adequate 
  descriptions 
  and 
  figures 
  of 
  the 
  internal 
  structure 
  

   of 
  many 
  species 
  have 
  not 
  been 
  published. 
  

  

  Thalassema 
  Lamarck.^ 
  — 
  The 
  geiuis 
  has 
  been 
  restricted 
  to 
  a 
  few 
  

   species 
  grouped 
  around 
  the 
  type, 
  Thalassema 
  thalassema 
  (Pallas), 
  

   generally 
  known 
  as 
  lli. 
  neptuni 
  Gaertner. 
  The 
  middle, 
  longitudinal 
  

   layer 
  of 
  muscle 
  fibers 
  of 
  body 
  wall 
  shows 
  no 
  sign 
  of 
  differentiation 
  

   into 
  thicker 
  bands. 
  The 
  internal 
  opening 
  of 
  the 
  nephridia 
  is 
  very 
  

   simple, 
  without 
  prolongation 
  into 
  si)irally 
  coiled 
  lips. 
  

  

  ANELASsoRHYNrHis 
  Aiuiandale 
  (1922, 
  p. 
  148). 
  — 
  It 
  may 
  not 
  be 
  of 
  

   any 
  practical 
  value 
  to 
  recognize 
  this 
  group. 
  The 
  species 
  dilfer 
  from 
  

   Thalassema 
  in 
  having 
  the 
  nephrostome 
  lips 
  j)rolonged 
  and 
  spirally 
  

   coiled, 
  but 
  little 
  is 
  known 
  of 
  other 
  details 
  of 
  the 
  internal 
  anatomy. 
  

   Amiundalc 
  based 
  the 
  genua 
  on 
  the 
  structure 
  of 
  the 
  |)r()boscis 
  of 
  four 
  

   cstuarinc 
  species 
  occiiniiig 
  in 
  lnackish 
  water 
  of 
  India 
  and 
  Siam. 
  

   He 
  says: 
  

  

  The 
  genus 
  con.sists 
  of 
  Kchiuridae 
  allied 
  to 
  ThnlnHmma 
  Gaertner, 
  but 
  differing 
  

   in 
  the 
  structure, 
  function, 
  and 
  phy.siology 
  of 
  tlic 
  proboscis. 
  Thi.s 
  organ 
  is 
  rela- 
  

   tively 
  stout 
  and 
  short, 
  incapable 
  of 
  great 
  prolongation 
  or 
  autotomy. 
  The 
  ciliated 
  

  

  