﻿268 
  Transactions. 
  — 
  Zuoloijy, 
  

  

  The 
  discovery 
  of 
  Desis 
  rohsoni, 
  and 
  its 
  highly 
  aquatic 
  and 
  marine 
  habits, 
  

   clear 
  up 
  Dr. 
  Koch's 
  doubts 
  as 
  to 
  the 
  voluntarily 
  aquatic 
  habitat 
  of 
  Desis 
  

   martensii. 
  

  

  In 
  reply 
  to 
  some 
  enquiries 
  of 
  mine, 
  Mr, 
  Eobson 
  gives 
  the 
  following 
  

   additional 
  mformation 
  as 
  to 
  the 
  mode 
  of 
  life 
  of 
  this 
  interesting 
  spider 
  :— 
  

  

  " 
  The 
  nests 
  of 
  this 
  spider 
  do 
  not, 
  in 
  my 
  opinion, 
  occur 
  below 
  low 
  water; 
  

   but 
  it 
  is 
  difficult 
  to 
  state 
  positively. 
  The 
  mouth 
  of 
  the 
  Lithodomiis 
  hole 
  in 
  

   which 
  the 
  nest 
  is 
  made 
  is 
  often, 
  if 
  not 
  always, 
  under 
  low 
  water 
  in 
  a 
  tidal 
  

   pool, 
  and 
  the 
  nest 
  is 
  only 
  to 
  be 
  got 
  at 
  by 
  breaking 
  up 
  the 
  rock 
  with 
  a 
  heavy 
  

   hammer. 
  The 
  spider, 
  when 
  going 
  to 
  the 
  bottom 
  of 
  a 
  pool, 
  on 
  being 
  dis- 
  

   turbed, 
  does 
  not 
  take 
  down 
  an 
  air-bubble 
  so 
  far 
  as 
  I 
  could 
  see, 
  and 
  is 
  able 
  

   to 
  live 
  a 
  considerable 
  time 
  without 
  air 
  or 
  only 
  the 
  small 
  amount 
  to 
  be 
  found 
  

   in 
  sea-water. 
  I 
  have 
  kept 
  them 
  alive 
  for 
  several 
  days 
  in 
  a 
  bottle 
  quite 
  full. 
  

   The 
  cocoons 
  of 
  eggs 
  are 
  found 
  at 
  the 
  end 
  of 
  the 
  hole 
  and 
  always 
  quite 
  dry. 
  

   I 
  have 
  not 
  seen 
  these 
  spiders 
  at 
  any 
  place 
  but 
  Cape 
  Campbell, 
  and 
  there 
  

   not 
  far 
  above 
  low- 
  water 
  mark, 
  there 
  being 
  many 
  feet 
  of 
  water 
  over 
  the 
  

   rocks 
  in 
  which 
  they 
  live 
  at 
  high 
  tide." 
  

  

  Further 
  observations 
  on 
  the 
  habits 
  of 
  this 
  spider 
  are 
  desirable. 
  An 
  

   examination 
  of 
  their 
  nests 
  might 
  disclose 
  the 
  nature 
  of 
  their 
  food. 
  Also, 
  if 
  

   Mr. 
  Eobson 
  is 
  correct 
  in 
  stating 
  that 
  the 
  mouths 
  of 
  the 
  holes 
  in 
  which 
  they 
  

   live 
  are 
  always 
  below 
  low 
  water, 
  how 
  are 
  they 
  supplied 
  with 
  aii' 
  ? 
  A 
  careful 
  

   comparison 
  of 
  Desis 
  robsoni 
  with 
  Koch's 
  description 
  and 
  figures 
  of 
  Desis 
  

   martensii, 
  shows 
  that 
  these 
  two 
  spiders 
  differ 
  very 
  slightly. 
  The 
  posterior 
  

   pair 
  of 
  legs 
  are 
  much 
  shorter 
  relatively 
  in 
  Desis 
  robsoni. 
  The 
  posterior 
  row 
  

   of 
  eyes 
  in 
  Desis 
  martensii 
  are 
  concave 
  anteriorly, 
  in 
  D. 
  robsoni 
  very 
  slightly 
  

   concave 
  posteriorly. 
  The 
  process 
  on 
  the 
  radial 
  joint 
  of 
  the 
  male 
  palpus 
  

   differs 
  in 
  form 
  in 
  the 
  two 
  species, 
  and 
  there 
  are 
  only 
  six 
  teeth 
  to 
  the 
  upper 
  

   border 
  of 
  the 
  fang 
  groove 
  in 
  Desis 
  robsoni, 
  there 
  being 
  seven 
  in 
  Desis 
  

   martensii. 
  Walckenaer's 
  diagnosis 
  of 
  the 
  genus 
  founded 
  on 
  a 
  single 
  species 
  

   needs 
  revision 
  now 
  that 
  three 
  more 
  species 
  have 
  been 
  discovered. 
  The 
  

   arrangement 
  and 
  relative 
  proportionate 
  size 
  of 
  the 
  eyes 
  and 
  the 
  length 
  of 
  

   the 
  legs 
  vary 
  from 
  the 
  characters 
  as 
  laid 
  down 
  by 
  him 
  in 
  the 
  Histoire 
  des 
  

   Apteres. 
  

  

  DESCEIPTION 
  OF 
  PLATE 
  Xn. 
  

  

  Desis 
  robsoni. 
  

  

  1. 
  Male, 
  showing 
  form 
  and 
  relative 
  proportions 
  of 
  ceplialothorax 
  and 
  falces. 
  

  

  2. 
  Lateral 
  view 
  to 
  show 
  elevation 
  of 
  ceplialathorax, 
  female. 
  

  

  3. 
  Anterior 
  view 
  of 
  caput 
  showing 
  arrangement 
  of 
  eyes. 
  

  

  4. 
  Sternum, 
  hp, 
  maxilla, 
  and 
  falx, 
  female. 
  

  

  5. 
  Epigyue, 
  female. 
  

  

  6. 
  Eadial 
  and 
  digital 
  joints 
  of 
  palpus, 
  male, 
  as 
  from 
  beneath, 
  b 
  from 
  outer 
  side, 
  c 
  

   extremity 
  of 
  radial 
  joint. 
  

  

  