﻿SPONGIIDA. 
  421 
  

  

  65. 
  Rhizochalina 
  singaporensis, 
  Carter, 
  ysit. 
  (Plate 
  XLI. 
  fig. 
  s.) 
  

  

  Pliloeodictyon 
  siugaporeuse, 
  Carter, 
  Ann. 
  ^ 
  Max). 
  N. 
  H. 
  (1883) 
  xii. 
  

   p. 
  326, 
  pi. 
  xiii. 
  tig. 
  17. 
  

  

  "With 
  this 
  species 
  I 
  identify 
  a 
  series 
  of 
  specimens 
  which 
  usually 
  

   have 
  tlie 
  outward 
  habit 
  of 
  2i.Jistulo.sa, 
  but 
  in 
  winch 
  a 
  large 
  pro- 
  

   portion 
  of 
  the 
  (usually 
  acerate) 
  spicules 
  have 
  both 
  ends 
  more 
  or 
  less 
  

   rounded. 
  In 
  the 
  most 
  perfect 
  specimen 
  the 
  cortex 
  is 
  glabrous, 
  

   chestnut 
  to 
  purplish-brown 
  in 
  colour, 
  thin 
  ; 
  the 
  fistuhe 
  are 
  wanting 
  

   on 
  one, 
  presumably 
  the 
  lower, 
  surface. 
  A 
  smaller 
  specimen 
  consists 
  

   of 
  a 
  barrel-shaped 
  mass 
  adherent 
  by 
  its 
  lower 
  surface 
  to 
  two 
  other 
  

   sponges, 
  and 
  giving 
  off 
  from 
  one 
  lateral 
  extremity 
  one, 
  from 
  the 
  

   other 
  two 
  fistulie 
  and 
  no 
  others. 
  A 
  detached 
  fistula 
  exhibits 
  

   furcation, 
  dividing 
  into 
  two 
  unequal 
  branches 
  at 
  an 
  angle 
  of 
  about 
  

   3U° 
  to 
  each 
  other. 
  In 
  one 
  remarkable 
  specimen 
  the 
  central 
  part 
  of 
  

   the 
  body 
  is 
  elongate, 
  slightly 
  compressed, 
  and 
  measures 
  110 
  millim. 
  

   (4|- 
  inches) 
  in 
  its 
  present 
  length, 
  while 
  its 
  diameter 
  does 
  not 
  exceed 
  

   12 
  millim. 
  anywhere 
  ; 
  in 
  its 
  other 
  characters 
  it 
  agrees 
  well 
  with 
  

   the 
  above 
  specimens. 
  A 
  fragment 
  of 
  the 
  bulbous 
  part 
  of 
  a 
  large 
  

   specimen 
  shows 
  that 
  part 
  of 
  this 
  specimen, 
  when 
  perfect, 
  to 
  have 
  

   possessed 
  a 
  diameter 
  of 
  about 
  75 
  millim. 
  (3 
  inches). 
  

  

  The 
  ends 
  of 
  the 
  spicules 
  show 
  almost 
  every 
  stage 
  between 
  a 
  

   merely 
  blunted 
  point 
  and 
  a 
  rounded 
  end 
  like 
  that 
  of 
  the 
  base 
  of 
  an 
  

   ordinary 
  acuate 
  spicule 
  : 
  some 
  thin, 
  completely 
  acerate 
  forms, 
  which 
  

   occur 
  mixed 
  with 
  the 
  blunt 
  forms 
  in 
  the 
  subcortical 
  tissues, 
  are 
  

   perhaps 
  the 
  young 
  of 
  the 
  latter, 
  indicating 
  the 
  typical 
  shape 
  from 
  

   which 
  the 
  adult 
  spicules 
  have 
  diverged. 
  The 
  largest 
  adult 
  spicules 
  

   have 
  nearly 
  the 
  same 
  size 
  as 
  the 
  acerates 
  of 
  the 
  typical 
  form 
  of 
  

   R.Jistidosa, 
  viz. 
  -3 
  by 
  "0127 
  millim., 
  but 
  they 
  vary 
  immensely 
  in 
  

   lenr/th; 
  the 
  thin 
  acerates 
  measure 
  "28 
  by 
  -004 
  millim. 
  In 
  Carter's 
  

   specimen 
  the 
  acerates 
  measure 
  "3 
  by 
  -017, 
  the 
  blunt 
  forms 
  •04-"08 
  

   by 
  -004 
  millim. 
  

  

  Three 
  fistulse 
  retain 
  their 
  ends, 
  and 
  these 
  are 
  finger-like 
  and 
  

   closed. 
  

  

  Hab. 
  Prince 
  of 
  Wales 
  Channel, 
  West 
  and 
  Alert 
  Islands, 
  Torres 
  

   Straits, 
  7 
  fms. 
  

  

  Distribution. 
  Singapore 
  (Carter). 
  

  

  I 
  may 
  explain 
  that 
  I 
  had 
  at 
  first 
  distinguished 
  this 
  form 
  as 
  a 
  

   variety 
  of 
  R.Jistiilosa; 
  but 
  as 
  Mr. 
  Carter 
  has, 
  since 
  then, 
  published 
  

   a 
  description 
  of 
  it 
  as 
  a 
  distinct 
  species, 
  and 
  as 
  T 
  had 
  already 
  felt 
  

   that 
  it 
  should 
  perhaps 
  be 
  so 
  described, 
  I 
  assign 
  the 
  name 
  proposed 
  

   by 
  him 
  to 
  the 
  Australian 
  specimens. 
  

  

  56. 
  Rhizochalina 
  spathulifera. 
  

   (Plate 
  XXXIX. 
  fig. 
  E 
  ; 
  Plate 
  XLI. 
  fig. 
  q.) 
  

  

  Main 
  body 
  elongated, 
  flexuous, 
  cylindrical 
  or 
  somewhat 
  compressed, 
  

   12-17 
  millim. 
  in 
  greatest 
  diameter. 
  External 
  portion 
  (cortex) 
  in 
  dry 
  

   state 
  even, 
  hard 
  and 
  dense 
  on 
  the 
  stem, 
  where 
  it 
  is 
  about 
  -7 
  millim, 
  

   thick; 
  rather 
  uneven, 
  porous 
  atid 
  compressible 
  on 
  the 
  brandies; 
  

  

  