﻿220 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol.96 
  

  

  0^. 
  Body 
  wall 
  with 
  innermost 
  circular 
  layer 
  missing 
  or 
  degenerated 
  to 
  a 
  net 
  

   of 
  fibers; 
  no 
  anal 
  vesicles; 
  apparently 
  no 
  siphon; 
  no 
  proboscis 
  and 
  no 
  

   setae 
  Sactosomatida 
  » 
  

  

  Class 
  ECHIURIDA 
  

  

  KEY 
  TO 
  ORDERS 
  

  

  o'. 
  In 
  body 
  wall 
  longitudinal 
  muscle 
  layer 
  lying 
  between 
  outer 
  circular 
  layer 
  

   and 
  inner 
  oblique 
  layer; 
  nephridia, 
  normally 
  paired, 
  not 
  excessively 
  nu- 
  

   merous. 
  

  

  6*. 
  A 
  closed 
  blood- 
  vascular 
  system; 
  no 
  specialization 
  of 
  intestine 
  for 
  anal 
  

  

  respiration 
  Echiuroinea 
  Bock 
  (p. 
  220) 
  

  

  62. 
  No 
  vascular 
  system, 
  coelomic 
  fluid 
  being 
  heavily 
  charged 
  with 
  large 
  blood 
  

   corpuscles 
  containing 
  hemoglobin 
  or 
  hemoglobin 
  plus 
  hematin; 
  in- 
  

   testine 
  with 
  terminal 
  portion 
  enlarged, 
  thin-walled, 
  to 
  receive 
  water 
  

  

  from 
  cloacal 
  pump 
  Xenopneusta, 
  new 
  order 
  (p. 
  262) 
  

  

  a?. 
  Longitudinal 
  layer 
  of 
  body 
  wall 
  lying 
  outside 
  of 
  both 
  the 
  circular 
  layer 
  and 
  

   inner 
  obHque 
  layer; 
  nephridia 
  excessively 
  numerous, 
  unpaired 
  (and 
  with 
  

   terminal 
  nephrostome) 
  ; 
  proboscis 
  excessively 
  long. 
  

  

  Heteromyota,* 
  new 
  order 
  

  

  Order 
  Echiuroinea 
  Bock, 
  emended 
  

  

  A 
  closed 
  blood-vascular 
  system; 
  no 
  specialization 
  of 
  intestine 
  for 
  

   anal 
  respiration. 
  

  

  KEY 
  TO 
  FAMILIES 
  

  

  ci. 
  Dimorphic; 
  male 
  degenerate, 
  planarianlike, 
  parasitic 
  in 
  or 
  on 
  female; 
  female 
  

   resembling 
  Thalassema 
  but 
  with 
  bifid 
  proboscis 
  in 
  some 
  genera; 
  anal 
  vesicles 
  

   consisting 
  of 
  branched 
  tubules 
  ending 
  in 
  numerous 
  cihated 
  cups; 
  anterior 
  

   setae 
  sometimes 
  present; 
  posterior 
  setae 
  absent 
  Bonelliidae 
  (p. 
  249) 
  

  

  a?. 
  Not 
  dimorphic; 
  proboscis 
  usually 
  conspicuous, 
  sometimes 
  several 
  times 
  length 
  

   of 
  body, 
  but 
  never 
  bifid; 
  absent 
  in 
  one 
  genus; 
  anal 
  vesicles 
  not 
  branched 
  

   but 
  in 
  form 
  of 
  elongate 
  sacs, 
  surface 
  of 
  which 
  is 
  covered 
  with 
  minute 
  cilated 
  

   funnels; 
  anterior 
  paired 
  setae 
  present 
  in 
  all 
  genera, 
  posterior 
  setae 
  in 
  

   Echiurus 
  only 
  Echiuridae 
  (p. 
  221) 
  

  

  3 
  New 
  name 
  for 
  Saccosomatida 
  Thfiel 
  (1906, 
  p. 
  14). 
  Th§el 
  instituted 
  the 
  group 
  as 
  a 
  suborder 
  for 
  Sacco- 
  

   soma 
  vitreum 
  Danielssen 
  and 
  Koren 
  (1881, 
  p. 
  34, 
  pi. 
  6, 
  figs. 
  1-8). 
  This 
  species 
  is 
  based 
  on 
  a 
  single 
  small 
  

   example 
  dredged 
  in 
  1,215 
  fathoms 
  north 
  of 
  the 
  Faroe 
  Islands. 
  It 
  is 
  a 
  female 
  and 
  the 
  species 
  may 
  prove 
  to 
  

   be 
  dimorphic, 
  as 
  there 
  is 
  a 
  single 
  nephridium 
  filled 
  with 
  eggs 
  and 
  opening 
  near 
  the 
  mouth. 
  The 
  proboscis 
  

   may 
  have 
  been 
  lost. 
  It 
  is 
  aberrant 
  from 
  all 
  other 
  echiuroids 
  and 
  may 
  not 
  be 
  an 
  echiuroid. 
  Saccosoma 
  

   Danielssen 
  and 
  Koren 
  is 
  preoccupied 
  by 
  Saccosoma 
  Motschoulsify, 
  1859, 
  in 
  Coleoptera 
  (Bull. 
  Acad. 
  St. 
  

   Pfetersbourg, 
  vol. 
  1, 
  column 
  304). 
  The 
  new 
  name 
  "Sactosoma" 
  (with 
  identical 
  meaning) 
  is 
  proposed 
  to 
  

   replace 
  Saccosoma 
  Danielssen 
  and 
  Koren. 
  

  

  * 
  Based 
  on 
  the 
  remarkable 
  genus 
  Ikeda 
  Wharton, 
  1913, 
  pp. 
  243-270. 
  Type, 
  Thalassema 
  taenioides 
  Ikeda, 
  

   1904, 
  p. 
  63; 
  1907, 
  p. 
  16, 
  pi. 
  1, 
  fig. 
  3; 
  pi. 
  2, 
  figs. 
  18-22; 
  pi. 
  3, 
  figs 
  23-36; 
  pi. 
  4, 
  figs. 
  37-47. 
  This 
  large 
  echiuroid, 
  

   with 
  a 
  proboscis 
  upward 
  of 
  a 
  meter 
  or 
  more 
  in 
  length 
  and 
  nephridia 
  from 
  200 
  to 
  400 
  in 
  number 
  without 
  

   indication 
  of 
  paired 
  arrangement, 
  is 
  so 
  different 
  from 
  the 
  general 
  run 
  of 
  the 
  phylum 
  that 
  it 
  deserves 
  to 
  be 
  

   set 
  apart 
  as 
  the 
  type 
  of 
  at 
  least 
  a 
  distinct 
  order. 
  The 
  arrangement 
  of 
  muscle 
  layers 
  is 
  different 
  from 
  that 
  of 
  

   all 
  other 
  echiuroids 
  and 
  indicates 
  a 
  long 
  separation 
  from 
  typical 
  stock. 
  See 
  Sato, 
  1931. 
  p. 
  179. 
  

  

  