﻿474 
  

  

  COLLECTIONS 
  FROM 
  MELANESIA. 
  

  

  in 
  the 
  arm. 
  is 
  not 
  quite 
  constant 
  in 
  its 
  position. 
  The 
  rest 
  of 
  the 
  

   characters 
  agree 
  with 
  those 
  of 
  the 
  typical 
  form. 
  

  

  Hah. 
  West 
  Island, 
  Torres 
  Straits, 
  7 
  fms. 
  ; 
  bottom 
  sand. 
  

  

  Variations. 
  This 
  sponge 
  varies, 
  as 
  has 
  been 
  seen, 
  in 
  shape 
  (oval 
  

   or 
  subspherical) 
  and 
  in 
  the 
  presence 
  or 
  absence 
  of 
  a 
  vent. 
  A 
  third 
  

   variation 
  may 
  be 
  noted, 
  viz. 
  in 
  the 
  length, 
  stoutness, 
  and 
  amount 
  

   of 
  curve 
  in 
  the 
  arms, 
  and 
  in 
  stoutness 
  of 
  the 
  shaft 
  of 
  the 
  zone- 
  

   spicule 
  ; 
  thus 
  in 
  a 
  specimen 
  from 
  the 
  Arafura 
  Sea 
  the 
  diameter 
  of 
  

   the 
  shaft 
  falls 
  to 
  '045 
  millim., 
  that 
  of 
  the 
  arms 
  to 
  '043 
  millim., 
  the 
  

   length 
  of 
  the 
  arm 
  remaining 
  -25 
  millim., 
  while 
  the 
  backward 
  bend 
  of 
  

   the 
  arm, 
  though 
  gradual, 
  is 
  very 
  decided. 
  

  

  The 
  variations 
  in 
  this 
  spicule, 
  which 
  is 
  the 
  only 
  one 
  which 
  seems 
  

   to 
  differ 
  much 
  in 
  different 
  specimens, 
  are 
  as 
  follows 
  : 
  — 
  

  

  1. 
  Port 
  - 
  Darwin 
  speci- 
  

  

  men 
  

  

  2. 
  Thursday 
  Island 
  spe- 
  

  

  cimen 
  

  

  3. 
  Arafura 
  -Sea 
  speci- 
  

  

  men 
  

  

  4. 
  Var, 
  retroflexa 
  (West 
  

   Island, 
  Torres 
  Straits) 
  

  

  Curve 
  of 
  arm 
  

  

  slight, 
  gradual. 
  

  

  decided, 
  gradual, 
  

   sharp 
  near 
  end. 
  

  

  The 
  stellate 
  is 
  only 
  "013 
  to 
  -017 
  millim. 
  in 
  diameter 
  in 
  specimen 
  

   No. 
  3. 
  _ 
  

  

  The 
  species 
  differs 
  from 
  fS. 
  bacca, 
  Selenka, 
  in 
  the 
  small 
  size 
  of 
  the 
  

   stellate 
  spicule, 
  viz. 
  •02-*025 
  millim. 
  instead 
  of 
  '2 
  to 
  -4 
  millim. 
  in 
  

   diameter 
  ; 
  from 
  S. 
  tethyoj^sis, 
  Carter, 
  in 
  having 
  no 
  " 
  forks," 
  and 
  

   simple, 
  not 
  trifid, 
  arms 
  to 
  the 
  " 
  zone-spicule 
  ; 
  " 
  and 
  from 
  S. 
  gloho- 
  

   stellata, 
  id., 
  in 
  the 
  absence 
  of 
  a 
  globostellate 
  spicule 
  ; 
  for 
  distinctions 
  

   from 
  other 
  species 
  see 
  table 
  of 
  species 
  above. 
  The 
  largest 
  specimens 
  

   measure 
  about 
  25 
  millim. 
  (1 
  inch) 
  in 
  greatest 
  diameter 
  ; 
  all 
  the 
  

   specimens 
  are 
  preserved 
  in 
  spirit. 
  

  

  102. 
  Stelletta 
  clavosa 
  *. 
  (Plate 
  XLIII. 
  figs, 
  i, 
  i".) 
  

  

  Free, 
  subglobular 
  (very 
  occasionally 
  suboval). 
  A 
  single 
  circular 
  

   vent 
  is 
  almost 
  (if 
  not 
  quite) 
  invariably 
  present 
  ; 
  it 
  is 
  situate 
  either 
  

   on 
  a 
  flattened 
  or 
  depressed 
  area 
  ; 
  its 
  margin 
  apparently 
  forms 
  a 
  

   sphincter 
  ; 
  diameter 
  2 
  millim. 
  in 
  the 
  largest 
  specimens 
  received. 
  

   The 
  excretory 
  canals 
  unite 
  at 
  1-2 
  millim. 
  below 
  surface. 
  Colour, 
  in 
  

   well-preserved 
  spirit-specimens, 
  pale 
  purplish 
  grey 
  to 
  puce, 
  in 
  others 
  

  

  From 
  clavus, 
  a 
  nail, 
  in 
  allusion 
  to 
  the 
  fine 
  nail 
  -like 
  zone-spicule. 
  

  

  