﻿390 
  COLLECTIONS 
  FROM 
  MELANESIA. 
  

  

  Main 
  skeleton 
  forming 
  rectangular 
  meshes 
  ; 
  primary 
  fibres 
  strong, 
  

   running 
  at 
  right 
  angles 
  to 
  surface, 
  exhibiting 
  horny 
  margins 
  (which 
  

   may 
  form 
  as 
  much 
  as 
  one 
  third 
  of 
  total 
  thickness 
  of 
  fibre), 
  about 
  

   •2y 
  to 
  '35 
  millim. 
  apart, 
  "1 
  to 
  -18 
  millim, 
  thick. 
  Secondary 
  fibres 
  

   vertical 
  to 
  primaries, 
  at 
  about 
  the 
  same 
  intervals, 
  either 
  without 
  

   foreign 
  bodies 
  or 
  with 
  only 
  about 
  half 
  to 
  two 
  thirds 
  of 
  the 
  thickness 
  

   occupied 
  by 
  them 
  ; 
  in 
  the 
  former 
  case 
  -035 
  to 
  "043 
  millim. 
  thick, 
  ia 
  

   the 
  latter 
  •053 
  to 
  '1 
  millim. 
  thick. 
  Longitudinal 
  fibres 
  {^primanj 
  of 
  

   Marshall) 
  of 
  same 
  structure 
  as 
  primaries, 
  but 
  less 
  horny, 
  '18 
  to 
  '28 
  

   millim, 
  apart, 
  -14 
  to 
  -21 
  millim. 
  thick, 
  running 
  upwards 
  and 
  spread- 
  

   icg 
  out 
  somewhat 
  from 
  each 
  other. 
  Dermal 
  skeleton 
  composed 
  of 
  

   long 
  compound 
  fibres, 
  the 
  primaries 
  running 
  parallel 
  to 
  each 
  other 
  

   and 
  to 
  the 
  long 
  axis 
  of 
  the 
  sponge, 
  '35 
  to 
  -43 
  millim. 
  apart 
  ; 
  the 
  

   secondaries 
  extended 
  between 
  them 
  at 
  considerable 
  intervals 
  ; 
  pri- 
  

   maries 
  -14 
  to 
  -28 
  millim. 
  broad, 
  secondaries 
  -1 
  to 
  '14 
  millim., 
  the 
  

   horny 
  matter 
  of 
  the 
  former 
  usually, 
  of 
  the 
  latter 
  often, 
  obscured 
  by 
  

   the 
  foreign 
  bodies, 
  which 
  often 
  project 
  much 
  from 
  the 
  fibre. 
  Horny 
  

   substance 
  amber 
  -yellow. 
  Sarcode 
  amber-yellow, 
  transparent. 
  

   Foreign 
  bodies 
  of 
  fibres 
  small, 
  chiefiy 
  sand. 
  

  

  Ilab. 
  North-east 
  coast 
  of 
  Australia. 
  

  

  The 
  single 
  specimen 
  is 
  105 
  millim. 
  (41 
  inches) 
  high 
  by 
  65 
  millim. 
  

   greatest 
  width. 
  In 
  its 
  even 
  compact 
  surface 
  it 
  differs 
  from 
  all 
  other 
  

   Dysidece 
  except 
  D. 
  favosa, 
  Marshal], 
  with 
  which 
  it 
  also 
  agrees 
  in 
  

   the 
  large 
  development 
  of 
  the 
  tubular 
  form 
  which 
  it 
  exhibits. 
  The 
  

   strongly 
  horny 
  character 
  of 
  the 
  secondary 
  fibre, 
  however, 
  distin- 
  

   guishes 
  it 
  from 
  this 
  (as 
  from 
  most, 
  if 
  not 
  all 
  other) 
  species, 
  and 
  

   allies 
  it 
  to 
  Hircinia. 
  These 
  striking 
  characters, 
  and 
  the 
  good 
  pre- 
  

   servation 
  of 
  the 
  specimen, 
  seem 
  to 
  warrant 
  its 
  description. 
  

  

  18. 
  Psammopemma 
  densum, 
  Marshall, 
  var. 
  subfibrosa. 
  

   (Plate 
  XLI. 
  fig. 
  7t.) 
  

  

  Psammopemma 
  densum, 
  3Iarshall, 
  Zeitsch, 
  tviss, 
  Zool. 
  xxxv. 
  p. 
  113. 
  

  

  Agreeing 
  closely 
  in 
  size 
  and 
  external 
  characters 
  with 
  Marshall's 
  

   account 
  of 
  this 
  strange 
  form 
  is 
  a 
  specimen 
  in 
  spirit 
  in 
  the 
  present 
  

   collection. 
  It 
  has 
  the 
  size 
  and 
  almost 
  the 
  shape 
  of 
  a 
  horse-bean, 
  

   and 
  is 
  of 
  a 
  grey 
  colour. 
  The 
  dermal 
  membrane 
  contains 
  numerous 
  

   foreign 
  bodies, 
  but 
  is 
  in 
  parts 
  transparent, 
  though 
  fibrillatcd. 
  Owing 
  

   to 
  an 
  inferior 
  amount 
  of 
  contained 
  sand, 
  a 
  distinct 
  network 
  of 
  wholly 
  

   sandy 
  fibres 
  is 
  to 
  be 
  made 
  out, 
  which 
  Marshall 
  did 
  not 
  find 
  in 
  his 
  speci- 
  

   mens 
  ; 
  the 
  meshes 
  are 
  round, 
  about 
  -3 
  millim. 
  in 
  diameter, 
  in 
  the 
  

   natural 
  state 
  almost 
  filled 
  up 
  with 
  sarcode 
  containing 
  foreign 
  bodies. 
  

   Sarcode 
  very 
  pale 
  brown, 
  subtransparcut. 
  The 
  radiating 
  tubes 
  indi- 
  

   cated 
  in 
  Mai'shall's 
  figure 
  (0) 
  appear 
  to 
  me 
  possibly 
  to 
  represent 
  

   spaces 
  between 
  primary 
  fibres; 
  but 
  those 
  fibres 
  in 
  the 
  present 
  specimen 
  

   are 
  not 
  straight, 
  but 
  bend 
  right 
  and 
  left 
  to 
  meet 
  the 
  short 
  secondary 
  

   lines 
  ; 
  thus 
  a 
  vertical 
  section 
  of 
  the 
  sponge 
  exhibits 
  a 
  somewhat 
  

   honeycomb-like 
  appearance. 
  No 
  trace 
  of 
  horny 
  matter 
  was 
  observed. 
  

  

  Hab. 
  Thursday 
  Island, 
  Torres 
  Straits, 
  3-4 
  fms. 
  

  

  Distrihittion. 
  Tasmania 
  (Marshall). 
  

  

  