﻿240 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM 
  vol.98 
  

  

  conspicuous 
  difference 
  between 
  the 
  littoral 
  regions 
  is 
  the 
  warmer 
  

   summer 
  of 
  Japan, 
  accompanied 
  by 
  a 
  tidal 
  exposure 
  occurring 
  at 
  a 
  

   more 
  unfavorable 
  time 
  of 
  day. 
  The 
  cooler, 
  overcast 
  summers 
  of 
  

   the 
  California 
  coast 
  offer 
  less 
  severe 
  conditions 
  of 
  exposure 
  to 
  many 
  

   marine 
  animals, 
  although 
  the 
  greater 
  wave 
  shock 
  of 
  the 
  California 
  

   coast 
  confines 
  many 
  species 
  to 
  more 
  sheltered 
  locations. 
  This 
  combi- 
  

   nation 
  of 
  factors 
  is 
  evidently 
  more 
  favorable 
  to 
  littoral 
  or 
  intertidal 
  

   pycnogonids 
  than 
  are 
  the 
  circumstances 
  prevailing 
  on 
  the 
  Japanese 
  

   coasts, 
  to 
  judge 
  from 
  the 
  number 
  of 
  species 
  known 
  at 
  present 
  

  

  This 
  is 
  in 
  substantial 
  agreement 
  with 
  Gislen's 
  summary 
  statement 
  

   (1944, 
  p. 
  81) 
  that 
  "on 
  the 
  whole, 
  however, 
  shorewater 
  life 
  has 
  much 
  

   better 
  possibilities 
  in 
  California 
  than 
  in 
  Japan," 
  although 
  it 
  is 
  more 
  

   stenothermic 
  on 
  the 
  California 
  coast. 
  Since 
  it 
  appears 
  that 
  most 
  

   pycnogonids 
  are 
  stenothermic, 
  it 
  is 
  not 
  surprising 
  that 
  there 
  are 
  so 
  

   many 
  more 
  intertidal 
  or 
  shallow 
  water-forms 
  known 
  on 
  the 
  California 
  

   coast, 
  although 
  there 
  is, 
  according 
  to 
  Gislen, 
  a 
  greater 
  number 
  of 
  

   species 
  on 
  the 
  Japanese 
  coast 
  in 
  certain 
  other 
  groups. 
  

  

  THE 
  GENUS 
  NYMPHON 
  

  

  A 
  much 
  better 
  view 
  of 
  the 
  distribution 
  of 
  pycnogonids 
  in 
  the 
  

   regions 
  under 
  consideration 
  can 
  be 
  had 
  from 
  an 
  examination 
  of 
  the 
  

   genus 
  Nym'phon^ 
  which 
  comprises 
  nearly 
  80 
  percent 
  of 
  the 
  collections 
  

   made 
  by 
  the 
  Albatross 
  and 
  perhaps 
  about 
  30 
  percent 
  of 
  the 
  species 
  

   occurring 
  in 
  the 
  North 
  Pacific. 
  Although 
  a 
  few 
  of 
  the 
  identifications, 
  

   such 
  as 
  Nymphon 
  niicronyx 
  from 
  Africa 
  Cape, 
  Kamchatka, 
  and 
  N. 
  

   macruTn 
  from 
  Sagami 
  Bay, 
  may 
  be 
  open 
  to 
  question, 
  the 
  general 
  dis- 
  

   tribution 
  picture, 
  as 
  illustrated 
  in 
  figure 
  19, 
  can 
  be 
  relied 
  upon. 
  It 
  

   is 
  possible 
  that 
  the 
  species 
  identified 
  by 
  Ohshima 
  (1936) 
  as 
  Nymphon 
  

   macrum 
  may 
  actually 
  be 
  a 
  specimen 
  of 
  Nymphon 
  japonicum^ 
  and 
  it 
  

   seems 
  best 
  to 
  ignore 
  this 
  identification 
  until 
  it 
  is 
  supported 
  by 
  more 
  

   material 
  or 
  adequate 
  figures. 
  

  

  There 
  are, 
  then, 
  at 
  least 
  15 
  species 
  of 
  Nymphon 
  present 
  in 
  Japanese 
  

   and 
  adjacent 
  waters. 
  Some 
  of 
  these 
  are 
  comparatively 
  abundant, 
  and 
  

   none 
  of 
  them 
  may 
  be 
  rare, 
  although 
  several 
  are 
  so 
  far 
  known 
  only 
  

   from 
  single 
  specimens. 
  No 
  other 
  genus 
  is 
  so 
  abundantly 
  represented, 
  

   insofar 
  as 
  actual 
  numbers 
  of 
  specimens 
  (or 
  "species-mass") 
  is 
  con- 
  

   cerned. 
  This 
  is 
  in 
  sharp 
  contrast 
  to 
  the 
  Atlantic 
  coast 
  of 
  North 
  

   America, 
  where 
  such 
  species 
  as 
  Tanystylum 
  orbiculare 
  and 
  Anoplo- 
  

   dactylus 
  lentus 
  are 
  often 
  collected 
  in 
  lots 
  of 
  50 
  or 
  more. 
  Of 
  course, 
  it 
  

   is 
  possible 
  that 
  some 
  littoral 
  species 
  are 
  as 
  abundant 
  on 
  the 
  Japanese 
  

   coast, 
  but 
  on 
  the 
  whole 
  the 
  picture 
  seems 
  to 
  be 
  that 
  of 
  widely 
  dis- 
  

   tributed 
  species 
  in 
  small 
  numbers, 
  except 
  for 
  the 
  genus 
  Nymphon. 
  

  

  As 
  can 
  be 
  seen 
  from 
  the 
  distribution 
  map 
  (fig. 
  19), 
  the 
  Japanese 
  

   Sea 
  derives 
  most 
  of 
  its 
  species 
  from 
  cold-water 
  regions, 
  but 
  at 
  least 
  

  

  