﻿SPONGIIDA. 
  367 
  

  

  tremcly 
  short, 
  and 
  deal 
  almost 
  invariably 
  with 
  the 
  mere 
  external 
  

   characters 
  of 
  the 
  forms 
  to 
  which 
  they 
  refer, 
  and 
  thus, 
  owing 
  to 
  the 
  

   well-known 
  variability 
  and 
  comparatively 
  slight 
  diagnostic 
  import- 
  

   ance 
  of 
  these 
  characters 
  in 
  the 
  Spongiida, 
  are 
  almost 
  useless, 
  per 
  se, 
  

   even 
  for 
  the 
  identification 
  of 
  species. 
  

  

  Thus 
  we 
  have 
  in 
  all 
  some 
  90 
  species 
  (allowing 
  for 
  synonyms}, 
  

   more 
  or 
  less 
  fully 
  described, 
  of 
  Sponges 
  chiefly 
  from 
  the 
  southern, 
  

   south-eastern, 
  and 
  south-western 
  coasts 
  of 
  Australia, 
  and 
  some 
  60 
  

   species 
  described 
  in 
  the 
  barest 
  manner, 
  probably 
  (but 
  not 
  certainly) 
  

   in 
  most 
  cases 
  from 
  the 
  northern 
  coasts, 
  and 
  a 
  few 
  from 
  the 
  south. 
  

  

  The 
  present 
  collection 
  comprises 
  upwards 
  of 
  300 
  specimens, 
  repre- 
  

   senting 
  110 
  species, 
  besides 
  7 
  distinct 
  varieties, 
  of 
  which 
  more 
  than 
  

   half 
  are 
  well 
  preserved 
  in 
  spirit 
  and 
  the 
  remainder 
  are 
  dry. 
  The 
  

   districts 
  searched 
  consist 
  of: 
  — 
  1. 
  Port 
  Jackson, 
  N.S.Wales; 
  2. 
  

   Several 
  points 
  on 
  the 
  north-east 
  coast 
  of 
  Queensland 
  ; 
  3. 
  Various 
  

   islands 
  and 
  spots 
  in 
  Torres 
  Straits 
  ; 
  4. 
  The 
  Arafura 
  Sea, 
  between 
  

   Cape 
  York 
  and 
  Port 
  Darwin; 
  5. 
  Port 
  Darwin, 
  N.W. 
  Australia. 
  

   The 
  depths 
  range 
  from 
  between 
  tide-mai'ks 
  to 
  36 
  fms. 
  (Arafura 
  Sea), 
  

   but 
  most 
  dredgings 
  did 
  not 
  exceed 
  20 
  fms. 
  in 
  depth. 
  

  

  It 
  is 
  perhaps 
  not 
  surprising, 
  after 
  what 
  has 
  been 
  stated 
  as 
  to 
  the 
  

   previous 
  work 
  which 
  has 
  been 
  done 
  among 
  the 
  Australian 
  Sponges, 
  

   to 
  find 
  that 
  a 
  large 
  proportion 
  (42 
  out 
  of 
  110, 
  or 
  38 
  per 
  cent.) 
  of 
  

   the 
  species 
  are 
  certainly 
  new 
  to 
  science, 
  and 
  that 
  a 
  considerable 
  

   number 
  more 
  may 
  possibly 
  prove 
  to 
  be 
  so, 
  having 
  been 
  assigned 
  only 
  

   doubtfully 
  to 
  described 
  species. 
  However, 
  the 
  distribution 
  of 
  the 
  

   littoral 
  species 
  (when 
  these 
  are 
  properly 
  defined 
  and 
  limited) 
  of 
  

   Sponges 
  appears 
  usually 
  to 
  be 
  but 
  moderately 
  wide, 
  and 
  perhaps 
  

   less 
  so 
  than 
  the 
  shallow-water 
  Alcyonaria 
  ; 
  both 
  this 
  and 
  another 
  

   fact 
  must 
  be 
  adduced 
  to 
  account 
  for 
  this 
  large 
  number 
  of 
  new 
  spe- 
  

   cies, 
  viz. 
  that 
  the 
  sponge-faunas 
  of 
  the 
  neighbouring 
  and 
  moderately 
  

   distant 
  seas 
  are 
  even 
  less 
  known 
  than 
  that 
  of 
  Australia 
  itself 
  ; 
  this 
  

   will 
  be 
  seen 
  clearly 
  from 
  a 
  statement 
  of 
  what 
  has 
  been 
  done 
  to 
  

   elucidate 
  the 
  fauna 
  of 
  the 
  Indian 
  Ocean 
  which 
  I 
  have 
  made 
  under 
  

   the 
  heading 
  Geographical 
  Distribution. 
  I 
  have 
  in 
  this 
  dearth 
  of 
  

   information 
  taken 
  pains 
  to 
  describe 
  every 
  form 
  which 
  warranted 
  

   description. 
  I 
  have 
  been 
  careful 
  not 
  to 
  assign 
  a 
  new 
  name 
  where 
  

   the 
  sponge 
  might 
  possibly 
  have 
  been 
  already 
  described, 
  in 
  order 
  not 
  

   to 
  run 
  the 
  risk 
  of 
  adding 
  to 
  the 
  overburdened 
  synonymy, 
  but 
  have 
  

   generally 
  given 
  a 
  full 
  description 
  in 
  such 
  cases, 
  so 
  that 
  no 
  doubt 
  

   might 
  remain 
  as 
  to 
  the 
  characters 
  of 
  that 
  species, 
  at 
  any 
  rate, 
  with 
  

   ■which 
  I 
  have 
  had 
  to 
  deal. 
  

  

  Taxonomy 
  of 
  the 
  Collection. 
  — 
  Of 
  the 
  1 
  10 
  species 
  obtained, 
  20 
  (or 
  

   more 
  than 
  one 
  sixth) 
  are 
  Ceratosa, 
  a 
  number 
  which 
  is 
  illustrative 
  of 
  

   the 
  largely 
  tropical 
  character 
  of 
  the 
  localities 
  from 
  which 
  they 
  are 
  

   drawn 
  ; 
  the 
  Dysideidsc 
  include 
  two 
  new 
  species 
  and 
  a 
  most 
  inter- 
  

   esting 
  variety 
  of 
  a 
  most 
  important 
  form, 
  Psammopemma 
  densum, 
  

   Marshall, 
  whose 
  nature 
  receives 
  hereby 
  confirmation 
  and 
  elucida- 
  

   tion 
  ; 
  the 
  number 
  of 
  new 
  Ceratosa 
  (4) 
  is 
  not 
  great, 
  as 
  most 
  of 
  the 
  

   species 
  seem 
  to 
  have 
  a 
  wide 
  range. 
  

  

  The 
  Silicea, 
  as 
  usual, 
  far 
  outnumber 
  the 
  other 
  groups 
  ; 
  the 
  

  

  