﻿478 
  C0LLECII0N8 
  FROM 
  MELANESIA. 
  

  

  fascicles 
  of 
  spicule-shafts, 
  a 
  ray 
  proceeding 
  from 
  the 
  head 
  of 
  each 
  of 
  

   the 
  latter, 
  extending 
  along 
  the 
  membrane 
  and 
  supporting 
  it 
  (see 
  

   fig. 
  I") 
  ; 
  in 
  some 
  parts 
  stout 
  acerate 
  spicules 
  (No. 
  2) 
  take 
  part 
  in 
  

   the 
  formation 
  of 
  the 
  dermal 
  skeleton. 
  Sarcode 
  transparent, 
  of 
  

   very 
  pale 
  brown 
  colour 
  ; 
  rendered 
  subopaque, 
  when 
  seen 
  in 
  the 
  

   mass, 
  by 
  immense 
  numbers 
  of 
  small 
  elongate 
  stellate 
  spicules. 
  

  

  Spicules 
  : 
  — 
  (1) 
  Triradiate 
  of 
  axis 
  and 
  dermal 
  skeleton, 
  consisting 
  

   of 
  a 
  straight 
  shaft 
  and 
  two 
  arms, 
  one 
  tapering 
  to 
  a 
  sharp 
  point 
  and 
  

   boldly 
  recurvate, 
  the 
  other 
  ending 
  abortively 
  in 
  a 
  rounded 
  extremity 
  

   shortly 
  after 
  its 
  origin 
  ; 
  the 
  arms 
  are 
  set 
  at 
  right 
  angles 
  to 
  the 
  

   shaft 
  and 
  at 
  angles 
  of 
  about 
  160° 
  to 
  each 
  other, 
  but 
  lie 
  in 
  different 
  

   planes. 
  Length 
  of 
  shaft 
  and 
  long 
  arm 
  probably 
  variable, 
  and 
  depend- 
  

   ing 
  on 
  the 
  position 
  of 
  the 
  spicule 
  ; 
  the 
  former 
  attains 
  a 
  length 
  of 
  5*5 
  

   millim., 
  the 
  latter 
  of 
  2 
  millim. 
  ; 
  diameter 
  about 
  '05 
  millim. 
  It 
  is 
  

   the 
  shaft 
  of 
  this 
  spicule 
  which 
  forms 
  the 
  longitudinal 
  skeleton-bands. 
  

   (2) 
  Large 
  acerate 
  of 
  dermal 
  skeleton, 
  slightly 
  curved, 
  tapering 
  from 
  

   centre 
  to 
  sharp 
  points 
  ; 
  size 
  about 
  1"8 
  by 
  •05--075 
  millim. 
  (3) 
  

   Minute 
  elongate 
  stellate 
  flesh-spicule, 
  consisting 
  of 
  a 
  straight 
  or 
  

   occasionally 
  curved 
  or 
  sinuous 
  cylindrical 
  shaft, 
  beset 
  with 
  numerous 
  

   irregular 
  blunt 
  processes, 
  about 
  20 
  to 
  the 
  spicule, 
  varying 
  in 
  length 
  

   from 
  -001 
  to 
  -002 
  millim., 
  thickness 
  about 
  -001 
  millim. 
  ; 
  length 
  of 
  

   spicule 
  about 
  -0095 
  millim., 
  thickness 
  of 
  shaft 
  alone 
  -001 
  millim. 
  

   Crowded 
  over 
  all 
  parts 
  of 
  the 
  soft 
  tissues. 
  

  

  Hab. 
  Port 
  Darwin, 
  7-12 
  fms., 
  bottom 
  sand 
  and 
  mud 
  ; 
  Torres 
  

   Straits, 
  10 
  fms., 
  bottom 
  sand. 
  

  

  Of 
  the 
  two 
  specimens 
  from 
  Port 
  Darwin 
  the 
  larger 
  is 
  74 
  millim. 
  

   (3 
  inches) 
  long 
  in 
  its 
  present 
  state, 
  viz. 
  without 
  its 
  original 
  base 
  

   and 
  with 
  the 
  apex 
  somewhat 
  abraded: 
  it 
  probably 
  did 
  not 
  much 
  

   exceed 
  this 
  length 
  when 
  perfect 
  ; 
  its 
  longest 
  diameter 
  (it 
  is 
  sub- 
  

   oblong 
  in 
  transverse 
  section) 
  is 
  8 
  millim., 
  its 
  shortest 
  5 
  millim., 
  at 
  

   the 
  present 
  base. 
  The 
  smaller 
  specimen 
  has 
  the 
  base 
  attached, 
  but 
  

   has 
  lost 
  the 
  apex 
  ; 
  it 
  is 
  almost 
  cylindrical, 
  and 
  has 
  a 
  diameter 
  of 
  

   about 
  3-5 
  millim. 
  throughout. 
  In 
  the 
  dermis 
  of 
  the 
  larger 
  speci- 
  

   men 
  no 
  acerates 
  have 
  been 
  found, 
  but 
  in 
  the 
  smaller 
  one 
  they 
  

   appear 
  to 
  replace 
  the 
  triradiates 
  in 
  this 
  place 
  ; 
  it 
  is 
  in 
  this 
  specimen 
  

   that 
  an 
  axial 
  canal 
  traverses 
  the 
  sponge. 
  The 
  specimen 
  from 
  Torres 
  

   Straits 
  is 
  a 
  fragment, 
  forming 
  the 
  base 
  of 
  a 
  specimen 
  almost 
  

   certainly 
  belonging 
  to 
  the 
  same 
  species, 
  but 
  very 
  imperfect. 
  Its 
  

   acerate 
  differs 
  from 
  that 
  of 
  the 
  typical 
  form 
  by 
  having 
  a 
  diameter 
  of 
  

   •075 
  instead 
  of 
  Oo 
  millim. 
  ; 
  the 
  flesh-spicule 
  shows 
  no 
  divergence. 
  

  

  The 
  species 
  differs 
  very 
  markedly 
  from 
  Stewart's 
  — 
  (1) 
  outwardly, 
  

   in 
  having 
  the 
  surface 
  level 
  instead 
  of 
  bearing 
  sharp 
  points 
  ; 
  (2) 
  

   inwardly, 
  in 
  the 
  presence 
  of 
  an 
  cuvial 
  cavity, 
  in 
  having 
  tri- 
  instead 
  

   of 
  quadriradiate 
  body-spicules, 
  and 
  in 
  having 
  a 
  dermal 
  acerate 
  ; 
  

   the 
  stellates 
  of 
  T. 
  columnifera, 
  further, 
  are 
  normal 
  globostellates 
  

   and 
  not 
  elongate, 
  as 
  here 
  ; 
  in 
  the 
  general 
  arrangement 
  of 
  the 
  

   skeleton 
  this 
  species 
  differs 
  by 
  possessing 
  a 
  number 
  of 
  longitudinal 
  

   lines, 
  instead 
  of 
  the 
  condensed 
  central 
  mass 
  of 
  that 
  species. 
  

  

  The 
  species 
  is 
  obviously 
  nearly 
  related 
  to 
  a 
  form 
  named 
  Tri- 
  

   hradiion 
  Schinidtii, 
  well 
  described 
  and 
  illustrated 
  as 
  the 
  type 
  of 
  

  

  