﻿A 
  MONOGRAPH 
  OF 
  THE 
  VICTORIAN 
  SPONGES. 
  53 
  

  

  compressed 
  laterally, 
  and 
  with 
  a 
  somewhat 
  flattened 
  upper 
  surface 
  on 
  which 
  are 
  

   several 
  true 
  oscula 
  each 
  surrounded 
  by 
  a 
  membranous 
  oscular 
  fringe. 
  The 
  sides 
  of 
  the 
  

   body 
  exhibit 
  a 
  number 
  of 
  narrow 
  ridges, 
  of 
  which 
  the 
  principal 
  ones 
  run 
  vertically, 
  

   branching 
  and 
  anastomosing 
  more 
  or 
  less 
  and 
  connected 
  by 
  less 
  pronounced, 
  more 
  or 
  

   less 
  transverse 
  ridges 
  ; 
  between 
  the 
  ridges 
  are 
  numerous 
  interspaces 
  of 
  irregularly 
  

   rounded 
  shape, 
  these 
  are 
  the 
  pseudopores. 
  The 
  height 
  of 
  the 
  whole 
  colony 
  is 
  only 
  

   about 
  10 
  mm. 
  and 
  the 
  greatest 
  breadth 
  about 
  6 
  mm. 
  (in 
  the 
  specimen 
  figured). 
  In 
  

   some 
  specimens 
  the 
  ridges 
  are 
  much 
  less 
  regularly 
  arranged, 
  and 
  the 
  oscular 
  fringes 
  

   not 
  so 
  well 
  developed. 
  The 
  ridges 
  are, 
  of 
  course, 
  the 
  outer 
  surfaces 
  of 
  the 
  outer 
  

   Ascon-tubes 
  of 
  the 
  colony. 
  The 
  colour 
  in 
  spirit 
  is 
  white. 
  

  

  The 
  canal 
  system 
  conforms 
  to 
  type 
  B 
  (described 
  on 
  p. 
  28) 
  and 
  is 
  illustrated 
  

   in 
  Figure 
  3, 
  Plate 
  IV. 
  

  

  (b.) 
  Arrangement 
  of 
  tJie 
  Skeleton. 
  — 
  The 
  skeleton 
  consists 
  of 
  triradiate 
  spicules 
  

   only, 
  arranged 
  in 
  the 
  usual 
  manner. 
  In 
  the 
  outer 
  Ascon-tubes 
  the 
  spicules 
  are 
  often 
  

   sagittal 
  and 
  the 
  basal 
  ray 
  then 
  points 
  downward 
  as 
  usual. 
  

  

  (c.) 
  The 
  Spicules 
  (PL 
  X., 
  Fig. 
  3). 
  — 
  The 
  triradiate 
  spicules 
  vary 
  considerably 
  in 
  

   form 
  according 
  to 
  their 
  position 
  in 
  the 
  sponge, 
  so 
  that 
  we 
  may 
  roughly 
  distinguish 
  

   between 
  deep 
  and 
  dermal 
  spicules. 
  The 
  dermal 
  spicules 
  are 
  sometimes 
  nearly 
  

   equiangular 
  and 
  equiradiate, 
  but 
  with 
  the 
  rays 
  strongly 
  curved 
  so 
  that 
  the 
  centre 
  of 
  

   the 
  spicule 
  is 
  uplifted 
  considerably 
  above 
  the 
  level 
  of 
  the 
  plane 
  in 
  which 
  the 
  apices 
  

   of 
  the 
  three 
  rays 
  lie. 
  The 
  rays 
  are 
  stout, 
  conical 
  and 
  not 
  very 
  sharply 
  pointed, 
  

   measuring 
  about 
  0*056 
  by 
  0*008 
  mm. 
  Very 
  frequently, 
  however, 
  the 
  dermal 
  spicules 
  

   become 
  markedly 
  sagittal, 
  the 
  lateral 
  (or 
  oral) 
  rays 
  embracing 
  a 
  much 
  wider 
  angle 
  

   (nearly 
  180° 
  in 
  some 
  cases) 
  and 
  curving 
  somewhat 
  towards 
  one 
  another, 
  while 
  the 
  

   basal 
  ray 
  may 
  be 
  elongated 
  to 
  about 
  0*1 
  mm. 
  The 
  deep 
  spicules, 
  lying 
  in 
  the 
  walls 
  

   of 
  the 
  internal 
  Ascon-tubes, 
  are 
  approximately 
  ecjuiangular 
  and 
  equiradiate, 
  with 
  the 
  

   rays 
  lying 
  pretty 
  much 
  in 
  one 
  plane, 
  so 
  that 
  the 
  spicule 
  would 
  lie 
  almost 
  or 
  quite 
  

   flat 
  on 
  a 
  plane 
  surface. 
  The 
  rays 
  are 
  straight 
  and 
  slender, 
  of 
  nearly 
  the 
  same 
  

   diaineter 
  all 
  along 
  until 
  close 
  to 
  the 
  apex 
  and 
  then 
  rather 
  abruptly 
  and 
  not 
  very 
  

   sharply 
  pointed. 
  They 
  measure 
  about 
  0*084 
  mm. 
  in 
  length 
  by 
  0"0042 
  mm. 
  in 
  

   diameter. 
  

  

  {(l.) 
  Affinities. 
  — 
  This 
  species 
  is 
  obviously 
  closely 
  related 
  to 
  L. 
  slipitata 
  and 
  I 
  

   should 
  not 
  be 
  at 
  all 
  surpriscnl 
  to 
  find 
  a 
  i)erfect 
  series 
  of 
  intcn-nKnliati^ 
  forms. 
  Typical 
  

   examples 
  of 
  each 
  are, 
  ho\V(>ver, 
  easily 
  distinguishable 
  by 
  their 
  external 
  appearance, 
  

   and 
  they 
  may 
  conveniently 
  receive 
  separate 
  names. 
  

  

  {e.) 
  Locality.— 
  ^BM 
  Port 
  Phillip 
  Heads. 
  (Coll. 
  J. 
  B. 
  Wilson.) 
  

  

  