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  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  

  

  BONELLIOPSIS, 
  new 
  genus 
  

  

  Diagnosis. 
  — 
  Differing 
  from 
  Bonellia 
  in 
  having 
  the 
  nephrostome 
  at 
  

   the 
  distal 
  end 
  of 
  the 
  nephridium 
  instead 
  of 
  near 
  the 
  base, 
  and 
  in 
  the 
  

   possession 
  of 
  a 
  much 
  shorter 
  presiphonal 
  foregut; 
  either 
  left 
  or 
  right 
  

   nephridium 
  developed; 
  females 
  with 
  two 
  ventral 
  setae; 
  males 
  without 
  

   setae. 
  

  

  Type, 
  Bonelliopsis 
  alaskana, 
  new 
  species. 
  

  

  BONELUOPSIS 
  ALASKANA, 
  new 
  species 
  

  

  Figure 
  16; 
  Plates 
  26, 
  27 
  

  

  Description. 
  — 
  Body 
  elongate, 
  subcylindrical, 
  blunt 
  at 
  both 
  ends, 
  

   20 
  to 
  65 
  mm. 
  long, 
  and 
  commonly 
  four 
  or 
  five 
  times 
  as 
  long 
  as 
  thick; 
  

   proboscis 
  of 
  usual 
  Bonellia 
  form 
  seldom 
  exceeding 
  body 
  length 
  and 
  

   usually 
  considerably 
  shorter. 
  Contracted 
  skin 
  verrucose, 
  the 
  verru- 
  

   cae 
  squarish, 
  not 
  obviously 
  larger 
  in 
  any 
  particular 
  region; 
  when 
  skin 
  

   is 
  stretched 
  the 
  verrucae 
  flatten 
  out 
  into 
  squarish 
  glandular 
  thicken- 
  

   ings 
  arranged 
  in 
  irregular 
  longiseries. 
  

  

  Figure 
  16. 
  — 
  Bonelliopsis 
  alaskana, 
  new 
  species: 
  Two 
  males, 
  the 
  upper 
  1.27 
  mm., 
  the 
  lower 
  

   1.9 
  mm. 
  long, 
  X 
  SO. 
  The 
  spermatheca 
  is 
  most 
  heavily 
  shaded; 
  the 
  lightly 
  stippled 
  is 
  

   parenchymatous 
  and 
  muscle 
  tissue; 
  sperm 
  duct 
  opens 
  at 
  anterior 
  (right) 
  end. 
  

  

  Body 
  wall 
  thin, 
  translucent. 
  Inner, 
  circular 
  layer 
  of 
  muscles 
  

   smooth, 
  but 
  in 
  the 
  region 
  of 
  foregut 
  where 
  the 
  layer 
  is 
  thickest 
  there 
  

   is 
  a 
  division 
  into 
  slender 
  fascicles. 
  

  

  Setae 
  2, 
  small, 
  nearly 
  straight, 
  situated 
  close 
  together 
  a 
  short 
  dis- 
  

   tance 
  behind 
  mouth 
  (4 
  mm. 
  in 
  specimen 
  44 
  mm. 
  long). 
  There 
  is 
  a 
  

   short 
  but 
  broad 
  interbasal 
  muscle 
  which 
  usually 
  presses 
  upon 
  the 
  

   nerve 
  cord 
  and 
  ventral 
  blood 
  vessel. 
  

  

  Nepliridium 
  1; 
  of 
  six 
  specimens 
  dissected 
  four 
  had 
  the 
  left 
  ne- 
  

   phridium 
  developed 
  and 
  two 
  had 
  the 
  right. 
  It 
  is 
  situated 
  close 
  to 
  the 
  

   nerve 
  cord 
  directly 
  behind 
  the 
  setae. 
  In 
  some 
  specimens 
  the 
  nephri- 
  

   diopore 
  is 
  conspicuous 
  externally. 
  The 
  nephrostome 
  is 
  conspicuous, 
  

   terminal, 
  with 
  amply 
  folded 
  lips. 
  When 
  the 
  nephridium 
  is 
  filled 
  

  

  