﻿450 
  COLLECTIONS 
  FROM 
  MELANESIA. 
  

  

  79. 
  Rhaphidophlus 
  arbor 
  escens, 
  (Plate 
  XL. 
  fig. 
  L 
  ; 
  

   Plate 
  XLII. 
  tigs. 
  «, 
  n 
  .) 
  

  

  Sponge 
  stipitate, 
  mucli 
  branched, 
  bush-like 
  ; 
  branches 
  angular 
  

   rather 
  than 
  cylindrical 
  ; 
  surface 
  nodular, 
  connected 
  by 
  frequent 
  

   horizontal 
  trabeculaj 
  at 
  right 
  angles 
  to 
  the 
  erect 
  branches. 
  The 
  

   average 
  diameter 
  of 
  the 
  stem 
  and 
  its 
  branches 
  is 
  4-5 
  millim. 
  The 
  

   cortical 
  incrustation 
  of 
  spicules 
  consists 
  of 
  a 
  layer 
  about 
  '5 
  millim. 
  

   thick, 
  the 
  outer 
  part 
  of 
  which 
  consists 
  of 
  loose 
  fascicles 
  of 
  the 
  

   smooth 
  spinulate 
  spicule, 
  with 
  the 
  pointed 
  ends 
  placed 
  outermost 
  ; 
  

   the 
  spicules 
  are 
  closely 
  approximated 
  to 
  each 
  other 
  below 
  the 
  

   surface, 
  between 
  the 
  intermarginal 
  canals, 
  but 
  their 
  distal 
  ends 
  

   diverge 
  and 
  spread 
  out 
  somewhat 
  at 
  the 
  surface, 
  and 
  between 
  

   them 
  appear 
  to 
  be 
  placed 
  the 
  pores 
  ; 
  the 
  intermarginal 
  canals, 
  

   as 
  stated, 
  lie 
  between 
  the 
  bases 
  of 
  these 
  fascicles. 
  The 
  deeper 
  

   part 
  of 
  this 
  layer 
  consists 
  of 
  Halichondrioid 
  spiculo-fibre, 
  about 
  6-8 
  

   spicules 
  broad, 
  with 
  small 
  roundish 
  or 
  polygonal 
  meshes, 
  which 
  seem 
  

   to 
  have 
  enclosed 
  small 
  canals 
  (probably 
  the 
  afferent 
  canals 
  leading 
  

   from 
  the 
  intermarginal 
  cavities 
  to 
  the 
  ciliated 
  chambers). 
  No 
  

   horny 
  matter 
  is 
  to 
  be 
  seen 
  in 
  this 
  part 
  of 
  the 
  skeleton, 
  the 
  extreme 
  

   fragility 
  of 
  which 
  forbids 
  the 
  idea 
  that 
  any 
  such 
  occurs 
  here 
  [on 
  

   the 
  contrary, 
  the 
  compressibility 
  and 
  readiness 
  with 
  which 
  the 
  

   spicules 
  and 
  fibres 
  must 
  be 
  able 
  to 
  move 
  upon 
  each 
  other 
  in 
  life, 
  

   owing 
  to 
  the 
  manner 
  of 
  their 
  aggregation, 
  point 
  to 
  a 
  probable 
  great 
  

   power 
  of 
  contractility 
  and 
  expansion 
  in 
  the 
  dermal 
  membrane, 
  with 
  

   important 
  consequences 
  to 
  the 
  pores, 
  intermarginal 
  cavities, 
  and 
  

   inhalent 
  canals 
  which 
  it 
  contains 
  ; 
  and 
  I 
  should 
  anticipate 
  that 
  good 
  

   spirit-specimens 
  would 
  show 
  the 
  strong 
  development 
  here 
  of 
  muscle- 
  

   cells, 
  such 
  as 
  has 
  been 
  shown 
  by 
  Prof. 
  Sollas 
  in 
  Tetilla 
  (Ann. 
  & 
  

   Mag. 
  N. 
  H. 
  1882, 
  ix. 
  p. 
  155)]. 
  The 
  fibres 
  of 
  the 
  skeleton 
  are 
  ir- 
  

   regular 
  ; 
  their 
  course 
  is 
  winding, 
  and 
  the 
  distinction 
  between 
  primary 
  

   and 
  secondary 
  fibres 
  not 
  clear, 
  except 
  at 
  the 
  surface 
  ; 
  here 
  the 
  ends 
  

   of 
  the 
  primary 
  fibres, 
  which 
  stand 
  out 
  for 
  some 
  distance 
  bej'ond 
  the 
  

   general 
  reticulum 
  and 
  support 
  the 
  dermal 
  crust, 
  are 
  absolutely 
  con- 
  

   cealed 
  by 
  the 
  enormous 
  abundance 
  of 
  points 
  of 
  the 
  spined 
  spicules 
  

   which 
  project 
  from 
  them. 
  

  

  Spicules 
  : 
  — 
  (1) 
  Slightly 
  spinulate, 
  smooth 
  acuate, 
  -34 
  by 
  -0063 
  ; 
  

  

  (2) 
  Spined 
  acuate, 
  slightly 
  constricted 
  basally, 
  -08 
  by 
  -0044 
  ; 
  

  

  (3) 
  Delicate 
  equianchorate, 
  palms 
  proximally 
  square, 
  -012 
  millim. 
  

   long. 
  

  

  Hah. 
  Friday 
  Island, 
  Torres 
  Straits. 
  

  

  The 
  specimen, 
  which 
  is 
  dry, 
  measures 
  125 
  millim. 
  (5 
  inches) 
  in 
  

   height 
  and 
  60 
  miUim. 
  (2^ 
  inches) 
  in 
  maximum 
  diameter. 
  

  

  Vosmaer's 
  ClatJiria 
  ulmns 
  (Notes 
  Hoy. 
  Mus. 
  Netherl. 
  ii. 
  p. 
  151) 
  

   resembles 
  this 
  species, 
  but 
  is 
  stated 
  to 
  have 
  a 
  bihamate 
  flesh- 
  

   spicule, 
  and 
  no 
  dermal 
  crust 
  is 
  described. 
  The 
  species 
  differs 
  from 
  

   R. 
  cratitiiis, 
  Esper, 
  in 
  the 
  well-branched 
  habit 
  and 
  in 
  minor 
  points 
  in 
  

  

  