﻿ECIIIUKOID 
  WORMS 
  OF 
  NORTH 
  PACIFIC 
  — 
  FISHER 
  233 
  

  

  TVk-— 
  U.S.N.M. 
  No. 
  20G00. 
  

  

  Type 
  locality. 
  — 
  Ei 
  Mogote, 
  near 
  La 
  Taz, 
  Baja 
  California, 
  low 
  tide, 
  

   March 
  22, 
  1940, 
  1 
  specimen, 
  Steinbeck 
  and 
  Ricketts, 
  

   Specimens 
  examined. 
  — 
  Eight 
  as 
  follows: 
  

  

  Albatross 
  station 
  2S2S, 
  Gulf 
  of 
  California, 
  2-1° 
  II' 
  30" 
  N., 
  109° 
  55' 
  W., 
  10 
  fath- 
  

   oms, 
  shells, 
  1 
  specimen. 
  

   La 
  Plata 
  Island, 
  Ecuador, 
  7-10 
  fathoms, 
  rocky 
  with 
  nuUipores, 
  2 
  specimens, 
  

  

  Allan 
  Hancock 
  Foundation. 
  

   Thurloe 
  Bay, 
  Baja 
  California, 
  S-10 
  fathoms, 
  rock 
  with 
  gorgonids, 
  1 
  specimen, 
  

  

  Allan 
  Hancock 
  Foundation. 
  

   Off 
  San 
  Francisquito 
  Bay, 
  Baja 
  California, 
  1G5 
  fathoms, 
  shale 
  and 
  gray 
  mud, 
  1 
  

  

  specimen, 
  Allan 
  Hancock 
  Foi^ndation. 
  

   Ensenada 
  de 
  San 
  Francisco, 
  Baja 
  California, 
  2-6 
  fathoms, 
  1 
  specimen, 
  .\llan 
  

  

  Hancock 
  Foundation. 
  

   .\gua 
  Verde 
  Bay, 
  Baja 
  California, 
  10 
  fathoms, 
  mud 
  and 
  coral, 
  1 
  specimen, 
  Allan 
  

  

  Hancock 
  Foundation. 
  

   Dewey 
  Channel, 
  San 
  Eugene 
  Point, 
  Mexico, 
  21-24 
  fathoms, 
  coralline, 
  rock, 
  I 
  

  

  specimen, 
  Allan 
  Hancock 
  Foundation. 
  

  

  Distribution. 
  — 
  Baja 
  California 
  to 
  Ecuador, 
  low 
  tide 
  to 
  1G5 
  fathoms. 
  

  

  Remarks. 
  — 
  Mr. 
  Ricketts 
  states 
  that 
  the 
  type 
  was 
  associated 
  with 
  

   living 
  Denfalivm 
  in 
  sandy 
  mud 
  a 
  short 
  distance 
  below 
  the 
  surface. 
  

   The 
  specimen 
  from 
  station 
  2828 
  has 
  the 
  intestine 
  filled 
  mth 
  small 
  

   fragments 
  of 
  shells. 
  

  

  As 
  this 
  species 
  belongs 
  in 
  the 
  restricted 
  genus 
  Thalassema, 
  it 
  

   naturally 
  resembles 
  Th. 
  thalassema. 
  The 
  gizzard, 
  stomach, 
  and 
  

   presiphonal 
  intestine 
  are 
  definitely 
  longer 
  in 
  the 
  latter 
  species 
  and 
  the 
  

   anal 
  vesicles 
  smaller, 
  although 
  with 
  such 
  extensible 
  structures 
  it 
  is 
  

   difficult 
  to 
  make 
  comparisons. 
  It 
  may 
  be 
  recorded 
  that 
  m 
  alcoholic 
  

   specimens 
  there 
  is 
  no 
  division 
  of 
  the 
  body 
  into 
  three 
  parts, 
  wliich 
  

   Lcigh-Sbarpe 
  (1928, 
  p. 
  501) 
  reports 
  as 
  a 
  characteristic 
  of 
  thalassema. 
  

   The 
  ecology 
  of 
  the 
  two 
  species 
  is 
  very 
  different. 
  Lankester 
  (1881. 
  

   J). 
  350) 
  found 
  thalassema 
  on 
  the 
  south 
  coast 
  of 
  Devonshire 
  "in 
  galleries 
  

   excavated 
  in 
  tlie 
  red 
  sandstone 
  (not 
  limestone) 
  which 
  is 
  exjiosed 
  at 
  

   spring 
  tides. 
  The 
  galleries 
  appear 
  to 
  be 
  those 
  formed 
  by 
  the 
  Lamel- 
  

   Hbranch 
  Gastrochaena 
  which 
  the 
  Thalassema 
  appropriates." 
  Leigh- 
  

   Sharpe 
  (1928, 
  {). 
  499) 
  reports 
  tlu- 
  species 
  from 
  borings 
  in 
  hmestono 
  

   made 
  by 
  the 
  mollusk 
  Saxicava, 
  Fl^^mouth 
  Sound. 
  

  

  Named 
  for 
  John 
  Steinbeck, 
  whose 
  expedition 
  to 
  the 
  Gulf 
  of 
  Cali- 
  

   fornia 
  collected 
  (lie 
  type. 
  

  

  Genus 
  LISTRIOLOBUS 
  W. 
  Fischer 
  

  

  Lislriolobua 
  Spenokl, 
  1012c, 
  p. 
  310 
  {noitien 
  nudum). 
  — 
  W. 
  Fisciiku, 
  1920n, 
  p. 
  210 
  

   (no 
  type). 
  (Type, 
  Listriolohux 
  hahamcnsia 
  Fischer.) 
  

  

  Diagnosis. 
  — 
  DifTcring 
  from 
  Thalassema, 
  sensu 
  stricto, 
  in 
  having 
  

   elongate, 
  s|)irally 
  (H)iled 
  lips 
  to 
  neplirostome 
  and 
  8 
  to 
  10 
  narrow 
  merid- 
  

   ional 
  thickening.s 
  of 
  the 
  middle, 
  loiigitudinnl 
  muscle 
  layer. 
  Differing 
  

   from 
  Ocheiostoma 
  in 
  having 
  the 
  inner 
  oMiciue 
  layer 
  a 
  smooth 
  con- 
  

  

  