﻿424 
  COLLECTIONS 
  FROM 
  MELANESIA. 
  

  

  Brit. 
  Spong. 
  iii. 
  p. 
  204, 
  pi. 
  Ixxiii. 
  fig. 
  15); 
  Vosmaer 
  notes 
  this 
  

   discrepancy. 
  

  

  The 
  British 
  form 
  of 
  Gellius 
  couclii 
  has 
  external 
  characters 
  similar 
  

   to 
  those 
  of 
  Halicliondria 
  elegantia, 
  and 
  differs 
  from 
  it 
  but 
  slightly 
  in 
  

   the 
  sjjiculation. 
  In 
  the 
  present 
  collection 
  occurs 
  a 
  specimen 
  with 
  

   very 
  similar 
  spiculation, 
  but 
  the 
  acerate 
  is 
  thinner 
  and 
  the 
  fibre 
  is 
  

   very 
  distinct, 
  the 
  spicules 
  being 
  united 
  by 
  a 
  yellow 
  substance 
  which 
  

   appears 
  beyond 
  the 
  spicules 
  on 
  each 
  side 
  of 
  the 
  fibre. 
  It 
  has 
  grown 
  

   over 
  a 
  Sertularian 
  Hydroid, 
  to 
  which 
  circumstance 
  it 
  probably 
  owes 
  

   its 
  elongate 
  cylindrical 
  form 
  (that 
  of 
  G. 
  couclii 
  is 
  usually 
  massive, 
  

   compact, 
  and 
  the 
  spiculo-fibre 
  is 
  loose). 
  The 
  vents 
  are 
  scattered 
  on 
  

   the 
  surface, 
  and 
  measure 
  only 
  about 
  - 
  millim. 
  in 
  diameter. 
  It 
  may 
  be 
  

   distinguished 
  as 
  var. 
  ceratina. 
  The 
  following 
  table 
  gives 
  the 
  pro- 
  

   portions 
  of 
  the 
  spicules 
  in 
  the 
  type 
  specimens 
  of 
  each 
  of 
  the 
  three 
  

   forms 
  here 
  united 
  : 
  — 
  

  

  Acerate. 
  Bihamate. 
  

  

  millim. 
  millim. 
  

  

  Hal. 
  couchi, 
  Bowerbank 
  . 
  . 
  -24 
  by 
  -Oil 
  -02 
  by 
  -0016 
  

  

  Hal 
  elegantia, 
  id 
  -2 
  by 
  -01 
  -025 
  by 
  -016 
  

  

  G. 
  couchi, 
  var. 
  ceratina. 
  ... 
  -23 
  by 
  •0063--0079 
  '025 
  by 
  -0016 
  

  

  Hab. 
  Arafura 
  Sea, 
  32-36 
  fms. 
  

  

  Distribution. 
  Straits 
  of 
  Malacca 
  {Bowerbank); 
  Cornwall 
  {Boiver- 
  

   hank). 
  

  

  59. 
  Gellius 
  varius. 
  

  

  Halichondria 
  varia, 
  Bowerbank, 
  P. 
  Z. 
  S. 
  1875, 
  p. 
  292. 
  

   Isodictya 
  virgata, 
  id. 
  I. 
  c. 
  p. 
  294. 
  

  

  The 
  above 
  two 
  species 
  must 
  be 
  united. 
  The 
  erect 
  cylindrical 
  form 
  

   of 
  well-grown 
  specimens 
  forms 
  a 
  good 
  external 
  distinctive 
  specific 
  

   character, 
  while 
  the 
  superior 
  diameter 
  (see 
  below) 
  of 
  the 
  skeleton- 
  

   spicule 
  readily 
  distinguishes 
  it 
  under 
  the 
  microscope. 
  Two 
  frag- 
  

   ments, 
  exhibiting 
  a 
  cylindrical 
  erect 
  habit, 
  occur 
  ; 
  the 
  skeleton-fibre 
  

   is 
  rigid 
  and 
  brittle, 
  even 
  in 
  spirit-specimens, 
  and 
  agrees 
  sufficiently 
  

   with 
  that 
  of 
  the 
  typical 
  specimens 
  ; 
  the 
  proportions 
  of 
  the 
  spicules 
  

   are 
  as 
  follows 
  : 
  — 
  

  

  Acerate. 
  Bihamate, 
  

  

  millim. 
  millim. 
  

  

  Hal. 
  varia 
  (type) 
  -22 
  by 
  -016 
  -025 
  to 
  -032 
  by 
  -0016 
  

  

  Isodictya 
  virgata 
  (type) 
  . 
  . 
  -22 
  by 
  -014 
  -025 
  by 
  -^21 
  

   G. 
  varia 
  (from 
  Pt. 
  Darwin) 
  -25 
  by 
  -015 
  -019 
  by 
  0015 
  

  

  Hab. 
  Port 
  Darwin, 
  8-12 
  fms. 
  

  

  Distribution. 
  Straits 
  of 
  Malacca 
  (Bowerbank). 
  

  

  60, 
  Gellius 
  fibulatus. 
  

  

  Reniera 
  fibulata, 
  Schnndt, 
  Adr. 
  Meer. 
  (1862), 
  p. 
  73 
  : 
  Atl. 
  Geh. 
  (1870), 
  

  

  p. 
  40. 
  

   ? 
  Isodictya 
  iugosa, 
  Bowerbank, 
  Mon. 
  Brit. 
  Spvny. 
  ii. 
  p. 
  206, 
  iii. 
  pi. 
  2. 
  

  

  tigs. 
  11-14. 
  

  

  