﻿144 
  COLLECTIONS 
  FROM 
  MELANESIA. 
  

  

  Arms 
  at 
  least 
  six 
  times 
  the 
  diameter 
  of 
  the 
  disk, 
  not 
  diminished 
  

   in 
  width 
  for 
  some 
  distance 
  out. 
  Just 
  beyond 
  the 
  disk 
  there 
  are 
  three 
  

   large 
  upper 
  and 
  four 
  much 
  shorter 
  sj^ines 
  : 
  the 
  lowest, 
  which 
  is 
  the 
  

   smallest, 
  is 
  very 
  small 
  ; 
  gradually 
  this 
  disappears, 
  and 
  then 
  the 
  

   following 
  one 
  gets 
  smaller 
  and 
  smaller 
  till 
  it 
  disappears. 
  The 
  upper 
  

   spines 
  are 
  faintly 
  echinulated 
  near 
  their 
  tip 
  ; 
  the 
  uppermost 
  but 
  

   one 
  is 
  generally 
  rather 
  the 
  longest, 
  but 
  is 
  never 
  more 
  than 
  equal 
  to 
  

   about 
  the 
  length 
  of 
  two 
  of 
  the 
  upper 
  arm-plates. 
  

  

  The 
  edge 
  of 
  the 
  genital 
  slit 
  is 
  fringed 
  by 
  some 
  elongated 
  plates 
  ; 
  

   the 
  bridge 
  is 
  pretty 
  wide 
  ; 
  the 
  mouth-shields 
  are 
  largo 
  and 
  stout, 
  

   rather 
  longer 
  than 
  broad, 
  and 
  have 
  a 
  notch 
  in 
  the 
  middle 
  of 
  their 
  

   inner 
  edge. 
  

  

  The 
  lower 
  arm-plates 
  have 
  pretty 
  even 
  sides 
  and 
  are 
  of 
  about 
  the 
  

   same 
  length 
  as 
  breadth 
  ; 
  the 
  tentacle-scale 
  is 
  only 
  distinct 
  at 
  the 
  

   proximal 
  end 
  of 
  the 
  arm. 
  The 
  upper 
  arm-plates 
  are 
  twice 
  as 
  broad 
  

   as 
  long, 
  broader 
  along 
  their 
  distal 
  than 
  their 
  proximal 
  edge. 
  

  

  General 
  colour 
  of 
  disk 
  yellowish 
  grey, 
  the 
  radial 
  shields 
  violet, 
  the 
  

   upper 
  arm-plates 
  washed 
  with 
  slate-grey 
  and 
  having 
  a 
  faint 
  white 
  

   line 
  along 
  their 
  middle 
  ; 
  the 
  spines 
  light-coloured, 
  but 
  darker 
  

   towards 
  their 
  tip 
  ; 
  the 
  actiual 
  surface 
  lighter 
  ; 
  the 
  mouth-shields 
  

   prominent 
  by 
  their 
  whiteness. 
  

  

  Port 
  Darwin. 
  

  

  23, 
  OpMothrix 
  darwini. 
  

  

  Disk 
  somewhat 
  pentagonal, 
  with 
  delicate 
  spines 
  on 
  its 
  upper 
  sur- 
  

   face, 
  but 
  the 
  radial 
  shields 
  naked. 
  Colour 
  light 
  jnuk, 
  green, 
  or 
  

   lemon 
  in 
  places, 
  with 
  a 
  few 
  dark 
  spots. 
  

  

  Length 
  of 
  arms 
  perhaps 
  not 
  more 
  than 
  six 
  or 
  seven 
  times 
  the 
  

   diameter 
  of 
  the 
  disk. 
  

  

  The 
  large 
  radial 
  shields 
  form 
  right-angled 
  triangles, 
  the 
  perpen- 
  

   dicular 
  side 
  being 
  separated 
  from 
  that 
  of 
  its 
  fellow 
  by 
  a 
  very 
  narrow 
  

   line 
  and 
  by 
  only 
  a 
  single 
  row 
  of 
  rare 
  spines 
  ; 
  a 
  slight 
  notch 
  sepa- 
  

   rates 
  the 
  plates 
  at 
  the 
  peripheiy 
  of 
  the 
  disk. 
  The 
  interradial 
  spaces 
  

   are 
  about 
  as 
  broad 
  as 
  the 
  base 
  of 
  the 
  radial 
  shields, 
  and 
  are 
  richly 
  

   covered 
  with 
  delicate 
  spinules, 
  these 
  extend 
  on 
  to 
  the 
  actinal 
  surface, 
  

   but 
  leave 
  a, 
  bare 
  band 
  bordering 
  the 
  genital 
  slits 
  ; 
  the 
  bridge 
  between 
  

   the 
  slits 
  is 
  narrow 
  ; 
  mouth-shields 
  broader 
  than 
  long, 
  somewhat 
  irre- 
  

   gularly 
  lozenge-shaped 
  in 
  form. 
  The 
  lower 
  arm-plates 
  are 
  very 
  regu- 
  

   larly 
  arranged, 
  and 
  are 
  only 
  slightly 
  oblong, 
  many 
  being 
  almost 
  

   completely 
  square. 
  The 
  upper 
  arm-plates 
  are 
  broader 
  than 
  long, 
  the 
  

   aboral 
  edge 
  three-sided, 
  the 
  adoral 
  sides 
  long, 
  and 
  the 
  consequent 
  

   form 
  that 
  of 
  a 
  not 
  very 
  regular 
  hexagon. 
  Four 
  or 
  five 
  arm-spines, 
  

   the 
  lowest 
  not 
  peculiarly 
  short, 
  and 
  the 
  uppermost 
  equal 
  to 
  five 
  

   upper 
  arm-x)lates 
  in 
  length, 
  echinulated 
  at 
  their 
  free 
  end. 
  There 
  

   appear 
  to 
  be 
  two 
  very 
  small 
  tentacle-scales. 
  

  

  The 
  larger 
  of 
  the 
  two 
  specimens 
  presents 
  the 
  following 
  markings 
  : 
  

   — 
  There 
  are 
  three 
  black 
  dots 
  on 
  each 
  of 
  the 
  mouth-shields 
  ; 
  some 
  of 
  

   the 
  lower 
  arm-plates 
  are 
  light 
  green, 
  the 
  adoral 
  edges 
  of 
  others 
  are 
  

   marked 
  by 
  a 
  black 
  spot, 
  and 
  this 
  is 
  rendered 
  the 
  more 
  conspicuous 
  

  

  