﻿174 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol. 
  103 
  

  

  Family 
  Dendrocoelidae 
  

   Genus 
  Dendrocoelopsis 
  Kenk 
  

  

  Dendrocoelopsis 
  piriformis, 
  new 
  species 
  

  

  Figure 
  23; 
  Plate 
  6, 
  Figure 
  3 
  

  

  Description. 
  — 
  Sexually 
  mature 
  specimens 
  of 
  this 
  rather 
  broad 
  and 
  

   plump 
  species 
  measure 
  up 
  to 
  15 
  mm. 
  in 
  length 
  and 
  3 
  mm. 
  in 
  width. 
  

   In 
  quietly 
  gliding 
  animals, 
  the 
  head 
  is 
  truncated, 
  with 
  a 
  convex 
  

   frontal 
  margin 
  (grasping 
  organ). 
  There 
  is 
  a 
  visible 
  subterminal 
  

   depression 
  corresponding 
  to 
  the 
  adhesive 
  surface 
  of 
  the 
  grasping 
  

   organ 
  or 
  sucker. 
  The 
  rounded 
  lateral 
  corners 
  of 
  the 
  head 
  are 
  formed 
  

   by 
  the 
  auricles, 
  which 
  protrude 
  only 
  little 
  laterally, 
  thus 
  causing 
  an 
  

   insignificant 
  narrowing 
  (neck) 
  to 
  appear 
  behind 
  them. 
  Behind 
  the 
  

   head, 
  the 
  body 
  margins 
  widen 
  gradually. 
  The 
  greatest 
  width 
  is 
  

   reached 
  at 
  the 
  level 
  of 
  the 
  mouth. 
  Behind 
  that 
  level, 
  the 
  body 
  tapers 
  

   again 
  to 
  a 
  bluntly 
  pointed 
  posterior 
  end. 
  When 
  the 
  animal 
  is 
  at 
  

   rest, 
  the 
  body 
  appears 
  short 
  and 
  wide, 
  about 
  pear-shaped, 
  the 
  body 
  

   margins 
  often 
  forming 
  a 
  wavy 
  or 
  irregular 
  contour. 
  Yoimg 
  specimens 
  

   are 
  more 
  slender 
  and 
  their 
  lateral 
  margins 
  are 
  more 
  nearly 
  parallel 
  

   when 
  they 
  are 
  in 
  gliding 
  motion. 
  At 
  rest, 
  however, 
  they 
  assume 
  the 
  

   same 
  pyriform 
  shape 
  as 
  the 
  adults. 
  In 
  short, 
  the 
  habit 
  of 
  the 
  species 
  

   may 
  be 
  described 
  as 
  resembling 
  that 
  of 
  European 
  and 
  Asiatic 
  repre- 
  

   sentatives 
  of 
  the 
  genus 
  Bdellocephala 
  Man, 
  with 
  which 
  it 
  has 
  in 
  com- 
  

   mon 
  the 
  broad 
  shape 
  and 
  the 
  anterior 
  grasping 
  organ. 
  

  

  The 
  two 
  eyes 
  are 
  situated 
  on 
  the 
  dorsal 
  side 
  of 
  the 
  head. 
  Their 
  

   distance 
  from 
  each 
  other 
  amounts 
  to 
  somewhat 
  more 
  than 
  one-third 
  

   the 
  width 
  of 
  the 
  head 
  at 
  the 
  level 
  of 
  the 
  eyes. 
  The 
  distance 
  of 
  each 
  

   eye 
  from 
  the 
  lateral 
  margin 
  is 
  smaller 
  than 
  the 
  distance 
  from 
  the 
  

   frontal 
  margin. 
  

  

  The 
  color 
  of 
  the 
  dorsal 
  side 
  is 
  usually 
  a 
  cloudy 
  brown 
  or 
  dark 
  

   brownish 
  gray. 
  In 
  some 
  specimens, 
  the 
  pigment 
  is 
  arranged 
  in 
  

   definite 
  longitudinal 
  stripes: 
  one 
  sharply 
  marked 
  median 
  stripe 
  flanked 
  

   on 
  each 
  side 
  by 
  a 
  light 
  (usually 
  yellow) 
  band 
  ; 
  laterad 
  to 
  this 
  band 
  the 
  

   body 
  darkens, 
  losing 
  its 
  pigment 
  again 
  near 
  the 
  lateral 
  margin. 
  In 
  

   other 
  specimens, 
  lacking 
  the 
  two 
  light 
  dorsal 
  bands, 
  the 
  back 
  may 
  be 
  

   either 
  uniformly 
  pigmented 
  or 
  may 
  show 
  a 
  more 
  or 
  less 
  distinct 
  darker 
  

   band 
  along 
  the 
  midline. 
  Young 
  specimens 
  and 
  striped 
  adults 
  clearly 
  

   show 
  the 
  finer 
  disposition 
  of 
  the 
  pigment 
  in 
  small 
  rounded 
  dots, 
  each 
  

   dot 
  apparently 
  corresponding 
  to 
  an 
  individual 
  pigment 
  cell. 
  

  

  The 
  pigment 
  pattern 
  of 
  the 
  dorsal 
  side 
  of 
  the 
  head 
  is 
  quite 
  charac- 
  

   teristic. 
  A 
  very 
  dark 
  field 
  between 
  the 
  eyes 
  extends 
  anteriorly 
  to 
  

   both 
  sides 
  of 
  the 
  grasping 
  organ. 
  The 
  area 
  above 
  the 
  organ 
  is 
  unpig- 
  

   mented 
  and 
  white, 
  and 
  so 
  are 
  the 
  two 
  elongated 
  ocular 
  areas 
  antero- 
  

  

  