﻿428 
  

  

  COLLECTIONS 
  FROM 
  MELANESIA. 
  

  

  somewhat 
  too 
  wide 
  a 
  scope, 
  it 
  is 
  at 
  the 
  same 
  time 
  true 
  that 
  a 
  resting 
  

   place 
  or 
  places 
  must 
  be 
  found 
  for 
  those 
  numerous 
  and 
  varied 
  species 
  

   which 
  are 
  intermediate 
  between 
  the 
  more 
  plainly 
  marked 
  genera 
  

   Desmacidon, 
  Esperia, 
  and 
  MyxiUa. 
  For 
  some 
  of 
  these 
  forms 
  older 
  

   genera 
  may 
  be 
  employed, 
  e.g. 
  Dirrhopalum^Plocamia) 
  for 
  A. 
  coriaceus 
  

   and 
  microcionides 
  (as 
  I 
  have 
  endeavoured 
  to 
  show 
  in 
  a 
  paper 
  " 
  On 
  

   the 
  Genus 
  Plocamia 
  &c.," 
  Journ. 
  Linn. 
  Soc, 
  Zool. 
  xv. 
  pp. 
  481, 
  482). 
  

   For 
  some 
  such 
  species 
  (ahyssi, 
  pldnctenoides) 
  Mr. 
  Carter 
  employs 
  

   the 
  old 
  term 
  Jlaliehondria 
  ; 
  but 
  the 
  type 
  of 
  Fleming's 
  genus 
  Ha- 
  

   Ikliondria 
  is 
  Sponc/ia 
  papillaris^ 
  Pallas, 
  which 
  appears 
  to 
  be 
  a 
  

   synonym 
  of 
  Halicliondria 
  {Amorphina^ 
  Schmidt) 
  ^?a«?'o^rt, 
  viz. 
  a 
  

   Eenierid 
  and 
  not 
  a 
  Desmaeidine, 
  and 
  so 
  the 
  genus 
  Halichondria, 
  if 
  

   maintained, 
  should 
  be 
  restricted 
  to 
  Renieridse. 
  

  

  AmpJiiJectus, 
  it 
  seems 
  to 
  me, 
  may 
  be 
  kept 
  with 
  advantage 
  for 
  

   forms 
  with 
  dentate 
  or 
  navicular 
  equianchorate 
  flesh-spicules, 
  with 
  

   smooth 
  skeleton-spicules 
  and 
  absence 
  of 
  anv 
  echinating 
  spicules 
  : 
  the 
  

   type 
  of 
  the 
  genus 
  is 
  Isodictya 
  gracilis 
  of 
  Bowerbank. 
  It 
  may 
  be 
  

   perhaps 
  necessary 
  to 
  admit 
  forms 
  in 
  which 
  the 
  tibiella 
  (when 
  pre- 
  

   sent) 
  is 
  slightly 
  spined, 
  as 
  in 
  Desmacidon 
  anceps, 
  Schmidt. 
  Vosmaer's 
  

   limitation 
  of 
  Desmacidon 
  to 
  species 
  with 
  horny 
  fibre 
  is 
  not 
  justified 
  

   by 
  the 
  species 
  he 
  has 
  assigned 
  to 
  it. 
  

  

  63. 
  AmpMlectus 
  tibiellifer. 
  (Plate 
  XLII. 
  figs, 
  t-t" 
  .) 
  

  

  Erect, 
  massive, 
  sessile 
  by 
  broad 
  base 
  ; 
  sponge 
  broader 
  than 
  high 
  

   and 
  higher 
  than 
  it 
  is 
  thick, 
  decreasing 
  in 
  thickness 
  towards 
  upper 
  

   margin, 
  which 
  presents 
  a 
  narrow 
  edge. 
  Sponge-mass 
  honeycombed 
  

   by 
  a 
  system 
  of 
  tortuous, 
  anastomosing 
  spaces, 
  3 
  millim. 
  and 
  upwards 
  

   in 
  diameter, 
  separated 
  in 
  most 
  cases 
  merely 
  by 
  trabeculte 
  of 
  sub- 
  

   stance. 
  Surface 
  perforated 
  by 
  the 
  closely-set 
  openings 
  of 
  the 
  above- 
  

   mentioned 
  spaces 
  ; 
  surface 
  of 
  sponge 
  and 
  of 
  the 
  trabecuLie 
  between 
  

   openings 
  even, 
  slightly 
  villous 
  in 
  spirit. 
  Texture 
  of 
  sponge 
  in 
  

   spirit 
  firm, 
  subelastic, 
  tough 
  ; 
  colour 
  dark 
  reddish 
  umber-brown. 
  

   Sarcode 
  pale 
  reddish 
  brown, 
  rather 
  soft. 
  Main 
  skeleton 
  consist- 
  

   ing 
  of 
  compact 
  spiculo-fibre 
  formed 
  of 
  spicule 
  no. 
  1, 
  sliowing 
  no 
  

   horny 
  uniting 
  substance, 
  about 
  3 
  to 
  6 
  spicules 
  broad, 
  irregular 
  ; 
  

   some 
  only 
  of 
  the 
  primary 
  fibres 
  go 
  straight 
  to 
  surface, 
  the 
  secon- 
  

   dary 
  fibres 
  usually 
  meet 
  the 
  primaries 
  at 
  acute 
  angles 
  ; 
  primaries 
  

   about 
  "5 
  millim. 
  apart. 
  Dermal 
  skeleton 
  consisting 
  of 
  a 
  network 
  

   of 
  spiculo-fibre 
  2 
  to 
  4 
  spicules 
  broad, 
  the 
  spicules 
  mostly 
  loosely 
  

   aggregated 
  ; 
  meshes 
  of 
  network 
  about 
  '35 
  millim. 
  apart. 
  

  

  Spicules 
  : 
  — 
  (1) 
  Skeleton 
  acuate, 
  strong, 
  smooth, 
  straight 
  or 
  slightly 
  

   curved 
  ; 
  base 
  rather 
  squarely 
  rounded, 
  shaft 
  cylindrical, 
  tapering 
  

   to 
  point 
  from 
  about 
  three 
  diameters 
  from 
  end; 
  size 
  -38 
  by 
  -014 
  

   millim. 
  (2) 
  Tibiella, 
  slender, 
  almost 
  straight 
  ; 
  shaft 
  smooth, 
  of 
  

   same 
  diameter 
  throughout, 
  passing 
  gradually 
  into 
  an 
  oval 
  smooth 
  

   head 
  about 
  half 
  as 
  thick 
  again 
  as 
  sh;ift; 
  size 
  -25 
  by 
  -0042 
  millim. 
  

   (thickness 
  of 
  head) 
  : 
  abundant 
  in 
  dermal 
  membrane 
  and 
  interior. 
  

   (3) 
  Equianchorate, 
  navicular 
  or 
  shuttle-shaped, 
  with 
  palms 
  rather 
  

  

  