﻿SPOITGIIDA. 
  613 
  

  

  2 
  millim. 
  thick, 
  which 
  form 
  the 
  boundaries 
  of 
  cavities 
  1-2 
  millim. 
  

   wide, 
  extending 
  parallel 
  to 
  the 
  surface 
  ; 
  the 
  intervals 
  between 
  the 
  

   trabeculte 
  are 
  more 
  or 
  less 
  tympanized 
  by 
  thin 
  transparent 
  mem- 
  

   branous 
  expansions. 
  Consistency 
  in 
  spirit 
  — 
  (a) 
  of 
  monticular 
  specimen 
  

   soft 
  and 
  elastic, 
  like 
  Turkey 
  sponge; 
  (6) 
  of 
  subcylindrical 
  specimens 
  

   tough, 
  parchment-like. 
  Colour 
  — 
  («) 
  almost 
  white, 
  (h) 
  dull 
  putty- 
  to 
  

   reddish 
  brown. 
  

  

  Main 
  skeleton 
  — 
  primary 
  fibres 
  approximately 
  vertical 
  to 
  surface, 
  

   •05 
  to 
  '07 
  millim. 
  thick, 
  -18 
  to 
  -35 
  millim. 
  apart 
  ; 
  secondaries 
  

   approximately 
  vortical 
  to 
  surface, 
  but 
  often 
  curved 
  ; 
  size, 
  as 
  

   primaries 
  ; 
  about 
  '18 
  to 
  -25 
  millim. 
  apart. 
  Dermal 
  membrane 
  in 
  

   («) 
  based 
  on 
  fibre 
  '035 
  to 
  •! 
  millim. 
  thick, 
  forming 
  oval 
  meshes 
  -1 
  to 
  

   •18 
  millim. 
  in 
  diameter 
  ; 
  in 
  {h) 
  fibre 
  "03.5 
  to 
  '088 
  millim. 
  thick, 
  

   meshes 
  '14 
  to 
  '3 
  millim. 
  wide, 
  oval 
  or 
  oblong. 
  Fibre 
  brown 
  of 
  

   various 
  shades, 
  axially 
  cored 
  by 
  one 
  to 
  four 
  series 
  of 
  spicule 
  no. 
  1, 
  

   echinated 
  abundantly 
  by 
  the 
  spined 
  acuate 
  spicules. 
  

  

  Spicules 
  : 
  — 
  (1) 
  Skeleton 
  acuate, 
  straight, 
  tapering 
  gradually 
  from 
  

   near 
  centre 
  to 
  sharp 
  point 
  on 
  the 
  one 
  hand 
  and 
  to 
  rounded 
  base 
  on 
  

   the 
  other 
  ; 
  base 
  about 
  two 
  thirds 
  the 
  diameter 
  of 
  centre, 
  and 
  carrying 
  

   a 
  few 
  very 
  small 
  spines 
  ; 
  size 
  of 
  spicule, 
  -15 
  to 
  -175 
  by 
  '0055 
  millim. 
  

   (2) 
  Spined 
  acuate, 
  straight, 
  tapering 
  gradually 
  from 
  base 
  to 
  sharp 
  

   point, 
  base 
  rather 
  rugose 
  ; 
  spines 
  sharp, 
  small 
  to 
  moderate-sized, 
  

   those 
  of 
  proximal 
  two 
  thirds 
  vertical 
  to 
  shaft, 
  rather 
  scanty, 
  those 
  

   of 
  apical 
  third 
  numerous, 
  recurvate 
  ; 
  size 
  of 
  spicule 
  -075 
  by 
  •0063 
  

   to 
  •OO 
  by 
  ^008 
  millim. 
  (3) 
  Equianchorate, 
  navicular, 
  shaft 
  almost 
  

   straight, 
  slender; 
  palms 
  as 
  seen 
  from 
  front 
  truncate 
  below, 
  sub- 
  

   pyramidal, 
  elongate 
  (each 
  more 
  than 
  one 
  third 
  the 
  total 
  length 
  of 
  

   the 
  spicule) 
  ; 
  tubercle 
  rather 
  elongate 
  ; 
  size 
  of 
  spicule, 
  -021 
  to 
  -032 
  

   millim. 
  (4) 
  Same 
  as 
  (3), 
  but 
  shaft 
  more 
  curved, 
  and 
  size 
  of 
  spicule 
  

   only 
  -Oil 
  miUim. 
  

  

  Hah. 
  Boudeuse 
  and 
  Etoile 
  Islands, 
  Amirante 
  group, 
  10-13 
  fms. 
  ; 
  

   bottom, 
  sand 
  or 
  coral. 
  

  

  The 
  two 
  externally 
  very 
  dififerent 
  forms 
  which 
  I 
  have 
  indicated 
  

   in 
  the 
  description 
  by 
  {a) 
  and 
  {!>) 
  agree 
  so 
  closely 
  in 
  their 
  microscopic 
  

   characters 
  that 
  I 
  do 
  not 
  feel 
  justified 
  in 
  separating 
  them, 
  even 
  

   varietally 
  ; 
  the 
  absence 
  of 
  a 
  tough 
  cortex 
  from 
  (a) 
  is 
  perhaps 
  due 
  to 
  

   some 
  local 
  circumstance. 
  

  

  The 
  greatest 
  vertical 
  thickness 
  of 
  the 
  largest 
  specimen 
  is 
  23 
  

   millim., 
  the 
  length 
  60 
  millim., 
  the 
  diameter 
  of 
  the 
  lateral 
  lobes 
  17 
  

   millim. 
  The 
  brown 
  specimens 
  have 
  a 
  strong 
  external 
  resemblance 
  

   to 
  small 
  specimens 
  of 
  the 
  Hippospongioi 
  with 
  meandrine 
  canals, 
  

   and 
  especially 
  to 
  H. 
  derasa, 
  mihi 
  (see 
  Part 
  I., 
  p. 
  382, 
  of 
  this 
  Report) 
  ; 
  

   also 
  to 
  fresh 
  specimens 
  of 
  Chalinopsis 
  clathrodes, 
  Schmidt 
  ; 
  and 
  to 
  

   a 
  specimen, 
  now 
  in 
  the 
  National 
  collection, 
  of 
  an 
  a])parently 
  MS. 
  

   species 
  allied 
  to 
  CJathria, 
  named 
  '^ 
  Spongia 
  multifora, 
  Dufr.," 
  but 
  

   which 
  is 
  quite 
  distinct 
  from 
  G. 
  decumhens, 
  owing 
  to 
  the 
  strongly 
  

   spined 
  skeleton-spicules. 
  The 
  very 
  slender 
  slvclcton 
  acuate 
  with 
  its 
  

   slightly 
  spined 
  head 
  is 
  an 
  unusual 
  feature 
  in 
  a 
  Clathria, 
  and 
  few 
  

   Clathrias 
  are 
  without 
  either 
  a 
  bihamato 
  or 
  tricurvate 
  flesh-spicule. 
  

   The 
  sessile 
  massive 
  habit 
  distinguishes 
  it 
  from 
  all 
  other 
  true 
  

  

  