﻿420 
  COLLECTIONS 
  FROM 
  MELANESIA. 
  

  

  matic 
  position, 
  which 
  Carter 
  (I.e.) 
  is 
  inclined 
  to 
  regard 
  as 
  among 
  

   the 
  RenieridiB, 
  I 
  notice 
  that 
  Rhizochalina 
  oleracea, 
  at 
  any 
  rate, 
  has 
  

   a 
  true 
  Chalinid 
  fibre 
  ; 
  1)ut 
  Bowerbank's 
  and 
  Carter's 
  species 
  never 
  

   approach 
  this 
  condition 
  more 
  closely 
  than 
  by 
  producing 
  a 
  few 
  

   scattered 
  compact 
  fibres, 
  wholly 
  composed 
  of 
  spicules, 
  like 
  those 
  of 
  

   some 
  Pachychdlince 
  : 
  but 
  the 
  greater 
  part 
  of 
  the 
  organization 
  is 
  

   Reuierid, 
  and 
  it 
  appears 
  to 
  approach 
  8chmidtia, 
  Balsamo-Crevelli. 
  

   On 
  the 
  other 
  hand, 
  Oceanapia, 
  which 
  seems 
  to 
  be 
  nearly 
  allied, 
  has 
  

   the 
  bihamate 
  spicule. 
  Taking 
  this 
  fact 
  in 
  conjunction 
  with 
  the 
  

   horny 
  fibre 
  of 
  Rh. 
  oleracea, 
  it 
  seems 
  to 
  me 
  best 
  to 
  place 
  the 
  two 
  

   genera 
  in 
  the 
  Desmacidiuidae. 
  

  

  54. 
  Rhizochalina 
  fistulosa, 
  Bowerhank\ 
  var, 
  infradensata, 
  nov. 
  

  

  ? 
  Alcyonium 
  putridosum, 
  Lamarck, 
  Mem. 
  Mus. 
  Hist. 
  Nat. 
  i. 
  p. 
  168. 
  

   DesDiacidon 
  fistulosa, 
  Bowerbank, 
  P. 
  Z. 
  S. 
  1873, 
  p. 
  19, 
  pi. 
  iv. 
  figs. 
  7, 
  8. 
  

  

  Two 
  more 
  or 
  less 
  imperfect 
  specimens 
  in 
  spirit, 
  the 
  largest 
  about 
  

   25 
  millim. 
  (1 
  inch) 
  across 
  the 
  body, 
  and 
  some 
  detached 
  dry 
  tubes. 
  

   An 
  arrangement 
  here 
  found, 
  which 
  1 
  have 
  not 
  seen 
  described 
  in 
  

   this 
  species, 
  is 
  that 
  of 
  a 
  dense 
  layer 
  of 
  the 
  skeleton-spicules, 
  packed 
  

   side 
  by 
  side, 
  at 
  right 
  angles 
  to 
  and 
  about 
  "25 
  to 
  "8 
  millira. 
  below 
  the 
  

   surface 
  of 
  the 
  sponge 
  — 
  below, 
  that 
  is 
  to 
  say, 
  the 
  superficial 
  Isodictyal, 
  

   or 
  rather 
  Halichondrioid 
  (in 
  Bowerbank's 
  sense) 
  network 
  containing 
  

   the 
  subcortical 
  crypts 
  and 
  other 
  cavities. 
  This 
  layer 
  recalls 
  the 
  verti- 
  

   cal 
  layer 
  of 
  small 
  subspinulates 
  of 
  Binalda 
  uberrima, 
  Schmidt, 
  only 
  

   that 
  it 
  is 
  not, 
  as 
  there, 
  placed 
  at 
  the 
  surface. 
  It 
  is 
  represented 
  in 
  

   the 
  type 
  specimen 
  of 
  the 
  species 
  by 
  a 
  layer 
  in 
  which 
  the 
  sjjicules 
  are 
  

   set 
  obliquely 
  to 
  the 
  surface 
  at 
  various 
  angles. 
  As 
  both 
  the 
  present 
  

   specimens 
  present 
  this 
  peculiarity, 
  I 
  think 
  it 
  well 
  to 
  establish 
  for 
  

   them 
  a 
  distinct 
  variety. 
  

  

  Oue 
  of 
  the 
  specimens 
  exhibits 
  the 
  small 
  crateriform 
  eminences 
  

   figured 
  on 
  the 
  outside 
  of 
  Bowerbank's 
  specimen, 
  but 
  the 
  other 
  does 
  

   not 
  ; 
  hence 
  they 
  probably 
  have 
  no 
  systematic, 
  and 
  but 
  little 
  physio- 
  

   logical 
  importance. 
  The 
  spicules 
  agree 
  closely 
  in 
  proportions 
  with 
  

   those 
  of 
  the 
  type. 
  

  

  Arafura 
  Sea, 
  Arafura 
  Sea, 
  

   Type 
  specimen. 
  Spec. 
  no. 
  1. 
  Spec. 
  no. 
  li. 
  

  

  Acerate 
  spicule. 
  . 
  -27 
  by 
  -01 
  1 
  to 
  -0127 
  -20 
  by 
  -Oil 
  -25 
  by 
  -012 
  mm. 
  

  

  Hah. 
  Arafura 
  Sea, 
  N,W. 
  coast 
  of 
  Australia, 
  32-36 
  fms.-; 
  bottom 
  

   mud, 
  sand, 
  and 
  shells. 
  

  

  Distrihiition. 
  Fremantle, 
  W. 
  Australia 
  (Botuerbaiik) 
  (the 
  typical 
  

   form). 
  

  

  The 
  dermal 
  membrane 
  of 
  one 
  of 
  the 
  specimens 
  contains 
  a 
  large 
  

   number 
  of 
  smooth 
  acerate 
  spicules 
  of 
  about 
  half 
  the 
  length 
  and 
  

   breadth 
  of 
  the 
  proper 
  spicules 
  ; 
  they 
  do 
  not 
  occur 
  below 
  the 
  mem- 
  

   brane, 
  nor, 
  apparently, 
  in 
  the 
  other 
  specimen. 
  A 
  similar 
  circum- 
  

   stance 
  occurs 
  in 
  R. 
  siac/aporensis 
  described 
  below 
  ; 
  in 
  that 
  case 
  a 
  

   number 
  of 
  short 
  blunt 
  cylindrical 
  spicules 
  occur 
  of 
  the 
  normal, 
  or 
  

   almost 
  the 
  normal 
  thickness, 
  but 
  only 
  one 
  half 
  to 
  two 
  thirds 
  the 
  

   length 
  of 
  the 
  adult 
  form. 
  

  

  