﻿422 
  Collections 
  from 
  Melanesia. 
  

  

  rather 
  brittle, 
  white, 
  marked 
  (at 
  any 
  rate 
  on 
  the 
  stem) 
  on 
  its 
  inner 
  

   surface 
  by 
  closely-sefc 
  elongate 
  or 
  reticulate 
  ridges 
  ; 
  covered 
  by 
  a 
  

   thin, 
  wrinkled, 
  paper-like, 
  pale 
  yellow-brown 
  membrane. 
  Branches 
  

   given 
  off' 
  towards 
  end 
  of 
  stem, 
  in 
  succession, 
  in 
  one 
  plane 
  ; 
  7-8 
  

   millim. 
  in 
  diameter 
  at 
  bases, 
  slightly 
  less 
  towards 
  apices, 
  25 
  to 
  60 
  

   millim. 
  (1 
  to 
  2j 
  inches) 
  long; 
  cylindrical 
  at 
  base, 
  becoming 
  compressed 
  

   at 
  apex 
  into 
  flattened 
  subcircular 
  or 
  knife-like 
  expansions, 
  about 
  

   10 
  to 
  12 
  millim. 
  in 
  width 
  and 
  l-o 
  millim. 
  in 
  thickness 
  ; 
  the 
  free 
  ends 
  

   often 
  (if 
  not 
  always) 
  imperforate. 
  Skeleton 
  of 
  cortex 
  a 
  rather 
  close 
  

   Halichondrioid 
  network, 
  with 
  meshes 
  "OT-'l-l 
  millim. 
  wide, 
  fibre 
  

   3 
  to 
  (i 
  or 
  7 
  spicules 
  broad. 
  Main 
  skeleton 
  below 
  cortex 
  coarsely 
  

   reticulate 
  with 
  immense 
  aggregations 
  of 
  spicules 
  into 
  coarse 
  spiculo- 
  

   nbre. 
  Sarcode 
  in 
  axial 
  tissues 
  brown, 
  transparent, 
  in 
  cortex 
  

   almost 
  colourless. 
  Spicules 
  smooth 
  acerate, 
  tapering 
  gradually 
  to 
  

   sharp 
  points 
  from 
  about 
  seven 
  diameters 
  from 
  ends 
  ; 
  size 
  '22 
  by 
  'OOQS 
  

   millim. 
  

  

  Hah. 
  Thursday 
  Island, 
  Torres 
  Straits, 
  4-5 
  fms. 
  ; 
  bottom 
  mud. 
  

  

  A 
  single 
  specimen, 
  175 
  millim, 
  (7 
  inches) 
  long, 
  composed 
  of 
  two 
  

   laterally 
  fused 
  specimens. 
  One 
  end 
  is 
  broken 
  across, 
  and 
  shows 
  the 
  

   interior 
  to 
  be 
  filled 
  with 
  flocculent 
  spiculo-tissue 
  ; 
  it 
  is 
  thus 
  doubtful 
  

   whether 
  this 
  end 
  bore 
  any 
  tubes. 
  This 
  species 
  differs, 
  in 
  its 
  very 
  

   drawn-out 
  form, 
  from 
  all 
  the 
  described 
  species 
  except, 
  perhaps, 
  

   Phlceodictyon 
  liondurasense 
  , 
  which 
  is 
  known 
  only 
  from 
  a 
  tubular 
  

   fragment 
  ; 
  but 
  the 
  spicules 
  of 
  that 
  species 
  are 
  considerably 
  smaller 
  

   than 
  those 
  of 
  this 
  form, 
  viz. 
  only 
  -16 
  by 
  '008 
  millim. 
  

  

  No 
  Chalinoid 
  or 
  even 
  Esperia-\\kQ 
  fibre 
  appears 
  to 
  occur 
  in 
  any 
  

   part 
  of 
  the 
  sponge. 
  

  

  57. 
  Rhizochalina 
  canalis. 
  

   (Plate 
  XXXIX. 
  fig. 
  F 
  ; 
  Plate 
  XLI. 
  fig. 
  r.) 
  

  

  Simple, 
  unbranched, 
  cylindrical 
  tubes, 
  straight 
  or 
  slightly 
  bent 
  near 
  

   middle. 
  Diameter 
  at 
  middle 
  about 
  10 
  millim. 
  (in 
  large 
  specimens), 
  

   gradually 
  (sometimes 
  very 
  slightly) 
  decreasing 
  towards 
  ends 
  ; 
  ends 
  

   finger-like, 
  closed, 
  3 
  to 
  4 
  millim. 
  broad. 
  Surface 
  somewhat 
  uneven. 
  

   Vents 
  apparently 
  represented 
  by 
  circular 
  perforations 
  of 
  cortex, 
  

   •5 
  to 
  "8 
  millim. 
  wide, 
  few, 
  scattered. 
  Cortex 
  in 
  dry 
  state 
  hard, 
  rather 
  

   brittle, 
  slightly 
  compressible 
  towards 
  ends, 
  dense 
  ; 
  colour 
  greyish 
  ; 
  

   thickness 
  about 
  '7 
  millim. 
  ; 
  outer 
  layer 
  hard, 
  about 
  '2 
  millim. 
  thick 
  ; 
  

   inner 
  layer 
  bast-like, 
  closely 
  reticulate, 
  about 
  -3 
  millim. 
  thick. 
  Axial 
  

   substance 
  ? 
  Skeleton 
  of 
  cortex 
  composed 
  of 
  very 
  strong 
  vertical 
  

   spiculo-fibres 
  5-12 
  spicules 
  broad, 
  interlacing 
  closely 
  at 
  the 
  surface 
  

   to 
  form 
  the 
  hard 
  outer 
  layer 
  ; 
  they 
  are 
  about 
  '14 
  to 
  -18 
  millim. 
  apart 
  

   and 
  about 
  "7 
  millim. 
  long 
  at 
  the 
  thickest 
  part 
  of 
  the 
  cortex, 
  being 
  

   met 
  at 
  their 
  inner 
  extremities 
  by 
  a 
  strong 
  secondary 
  fibre 
  (parallel 
  

   to 
  the 
  surface) 
  about 
  10 
  spicules 
  broad. 
  Sarcode 
  pale 
  brown, 
  trans- 
  

   parent. 
  Spicules 
  smooth 
  acerate, 
  becoming 
  rounded 
  off 
  (rather 
  than 
  

   tapering) 
  to 
  sharp 
  points 
  from 
  about 
  four 
  diameters 
  from 
  ends 
  ; 
  size 
  

   •27 
  by 
  -014 
  millim. 
  

  

  