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  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol. 
  ids 
  

  

  is 
  seen 
  in 
  the 
  genus 
  Dendrocoelum 
  Orsted 
  where, 
  however, 
  true 
  suckers 
  

   are 
  not 
  known. 
  In 
  general, 
  the 
  taxonomic 
  vahie 
  of 
  adhesive 
  organs 
  

   in 
  triclads 
  appears 
  to 
  be 
  subordinated 
  to 
  that 
  of 
  other 
  anatomical 
  

   structures. 
  I 
  therefore 
  tentatively 
  modify 
  the 
  definition 
  of 
  the 
  

   genus 
  Dendrocoelopsis 
  by 
  omitting 
  the 
  presence 
  of 
  a 
  sucker 
  as 
  a 
  

   generic 
  character, 
  to 
  include 
  the 
  species 
  described 
  as 
  Dendrocoelopsis 
  

   and 
  Amyadenium. 
  

  

  Dendrocoelopsis 
  pirijormis 
  differs 
  from 
  the 
  other 
  members 
  of 
  the 
  

   genus 
  (in 
  its 
  wider 
  extent) 
  in 
  several 
  characters: 
  It 
  is 
  pigmented, 
  

   whereas 
  the 
  others 
  lack 
  pigment 
  and 
  appear 
  white; 
  the 
  presence 
  of 
  

   two 
  eyes 
  differentiates 
  it 
  from 
  the 
  three 
  blind 
  species, 
  D. 
  vandeli, 
  D. 
  

   brementi, 
  and 
  D. 
  garmieri 
  and 
  from 
  the 
  many-eyed 
  D. 
  chattoni; 
  and 
  

   the 
  dorsal 
  position 
  of 
  the 
  testes 
  separates 
  it 
  from 
  D. 
  spinosipenis, 
  D. 
  

   vaginata, 
  D. 
  garmieri, 
  and 
  D. 
  alaskensis. 
  Apart 
  from 
  these 
  most 
  con- 
  

   spicuous 
  characters, 
  the 
  structure 
  of 
  the 
  male 
  copulatory 
  organ 
  of 
  D. 
  

   piriformis 
  is 
  distinctive. 
  

  

  Holotype.— 
  On 
  five 
  slides, 
  USNM 
  22334, 
  Moose 
  Creek, 
  on 
  Glenn 
  

   Highway, 
  milepost 
  186, 
  near 
  Alaska 
  Road 
  Commission 
  camp, 
  Aug. 
  

   U. 
  1950. 
  

  

  Distribution 
  and 
  Ecology. 
  — 
  Dendrocoelopsis 
  piriformis 
  is 
  a 
  eury- 
  

   thermic 
  species 
  and 
  inhabits 
  lakes 
  and 
  their 
  outlets 
  in 
  the 
  southern 
  

   part 
  of 
  Alaska 
  and 
  also 
  occurs 
  in 
  a 
  lake 
  near 
  Umiat. 
  

  

  Long 
  Lake, 
  on 
  Glenn 
  Highway, 
  milepost 
  85.9, 
  Aug. 
  11, 
  1950, 
  clear 
  water, 
  

   17.8° 
  C. 
  (near 
  bank) 
  ; 
  under 
  stones, 
  several 
  specimens, 
  two 
  of 
  them 
  mature. 
  

  

  Lake 
  on 
  Glenn 
  Highway, 
  milepost 
  88.1, 
  Aug. 
  11, 
  1950, 
  water 
  temperature 
  

   varying 
  with 
  depth 
  (near 
  bank, 
  19° 
  C.) 
  ; 
  under 
  stones, 
  several 
  specimens, 
  one 
  

   mature. 
  

  

  Lake 
  on 
  Glenn 
  Highway, 
  milepost 
  23.5 
  (see 
  pi. 
  8), 
  Aug. 
  13, 
  1950, 
  clear 
  water, 
  

   23.6° 
  C. 
  (near 
  bank) 
  ; 
  several 
  immature 
  specimens. 
  

  

  Stream 
  crossing 
  Glenn 
  Highway 
  at 
  milepost 
  147.2, 
  outlet 
  of 
  Snowshoe 
  Lake, 
  

   Aug. 
  14, 
  1950, 
  moderate 
  current, 
  water 
  somewhat 
  colored, 
  17.0° 
  C.; 
  one 
  young 
  

   specimen, 
  under 
  a 
  stone. 
  

  

  Moose 
  Creek, 
  on 
  Glenn 
  Highway, 
  milepost 
  186, 
  near 
  Alaska 
  Road 
  Commission 
  

   camp, 
  Aug. 
  14, 
  1950, 
  fast, 
  clear 
  stream, 
  16.2° 
  C; 
  under 
  stones, 
  two 
  mature 
  speci- 
  

   mens 
  (holotype). 
  

  

  Pippin 
  Lake, 
  on 
  Richardson 
  Highway, 
  milepost 
  84.4, 
  Aug. 
  15, 
  1950, 
  shallow 
  

   water 
  near 
  bank, 
  20° 
  C. 
  ; 
  under 
  stones, 
  many 
  specimens, 
  two 
  of 
  them 
  mature. 
  

  

  Fresh-water 
  lake 
  near 
  Umiat, 
  collected 
  by 
  P. 
  F. 
  Scholander, 
  Aug. 
  15, 
  1948; 
  

   18 
  specimens, 
  majority 
  belonging 
  to 
  the 
  plain 
  form, 
  1 
  with 
  distinct 
  stripes, 
  5 
  

   sexually 
  mature 
  (USNM 
  23678). 
  

  

  Dendrocoelopsis 
  alaskensis, 
  new 
  species 
  

  

  Figure 
  24; 
  Plate 
  6, 
  Figure 
  4 
  

  

  Description. 
  — 
  I 
  had 
  only 
  limited 
  material 
  of 
  this 
  species 
  and 
  none 
  

   of 
  the 
  animals 
  was 
  fully 
  mature. 
  The 
  largest 
  specimen 
  measured 
  20 
  

   mm. 
  in 
  length 
  and 
  4 
  mm. 
  in 
  width. 
  

  

  The 
  anterior 
  end 
  is 
  slightly 
  lobed, 
  with 
  a 
  convex 
  frontal 
  margin 
  

  

  