﻿SPONGIIDA. 
  591 
  

  

  bodies 
  are 
  constantly 
  present, 
  travex'sing 
  the 
  main 
  mass 
  of 
  the 
  

   skeleton 
  ; 
  these 
  fibres 
  are, 
  however, 
  much 
  less 
  abundant 
  than 
  in 
  

   the 
  original 
  specimen 
  of 
  Lamarck, 
  and 
  the 
  wall 
  of 
  the 
  sponge 
  is 
  

   thinner. 
  Abundant. 
  

  

  Hah. 
  Providence 
  and 
  Cerf 
  Islands, 
  Mascarenes, 
  and 
  Amiranto 
  

   group 
  ; 
  beach 
  to 
  24 
  fms. 
  

  

  Distribution. 
  " 
  Mediterranean 
  " 
  (^Lamarck) 
  ; 
  Zanzibar 
  (Hi/att). 
  

  

  3. 
  Hippospongia 
  sinuosa. 
  

  

  Spongia 
  sinuosa, 
  Pallas, 
  Elench. 
  Zooph. 
  p. 
  394 
  ; 
  Lamarck, 
  Ann. 
  Mus. 
  

  

  Hist. 
  Nat. 
  XX. 
  p. 
  371. 
  

   p 
  Spongia 
  feuestrata, 
  Lamarck, 
  torn, 
  cit, 
  p. 
  374. 
  

   Spongia 
  lapidescens, 
  subspecies 
  mauritiana, 
  Hyatt, 
  Mem. 
  Bost. 
  Soc. 
  

  

  ii. 
  p. 
  528, 
  

  

  Lamarck's 
  and 
  Pallas's 
  S. 
  sinuosa 
  seem, 
  by 
  their 
  descriptions, 
  to 
  

   be 
  referable 
  to 
  a 
  Hipposijongia 
  of 
  which 
  I 
  describe 
  two 
  forms 
  

   below. 
  S. 
  fenestrata, 
  Lamarck, 
  is 
  probably 
  a 
  more 
  sessile 
  and 
  in- 
  

   crusting 
  form 
  of 
  the 
  same 
  species. 
  The 
  question 
  of 
  identity 
  is 
  beset 
  

   with 
  great 
  difficulties, 
  owing 
  to 
  the 
  want 
  of 
  authentic 
  specimens 
  of 
  

   the 
  different 
  species 
  for 
  reference. 
  A 
  S2)ecimen 
  long 
  contained 
  in 
  the 
  

   National 
  collection, 
  and 
  labelled 
  S. 
  ma'andriformis 
  or 
  mceandrini- 
  

   formis, 
  differs 
  from 
  the 
  form 
  described 
  below 
  as 
  var. 
  mauritiana 
  

   mainlj' 
  in 
  its 
  somewhat 
  more 
  slender 
  fibre 
  (•016-'045 
  millim. 
  in 
  

   thickness) 
  ; 
  but 
  its 
  history 
  is 
  unknown. 
  

  

  AYith 
  regard 
  to 
  Pallas's 
  description, 
  I 
  would 
  remark 
  (1) 
  that 
  the 
  

   dry 
  skeleton 
  of 
  our 
  specimens 
  is 
  not 
  tender 
  ("tenera"), 
  but 
  hard 
  

   and 
  almost 
  incompressible 
  ; 
  (2) 
  it 
  attains 
  a 
  vertical 
  thickness 
  of 
  

   35 
  millim. 
  ; 
  (3) 
  the 
  cavities 
  meander 
  and 
  anastomose, 
  and 
  are 
  not 
  

   merely 
  " 
  oblongte 
  vel 
  cotyloidese 
  " 
  ; 
  (4) 
  the 
  colour 
  is 
  a 
  fine 
  amber- 
  

   yellow 
  ; 
  (5) 
  in 
  var. 
  mauritiana 
  the 
  fibres 
  are 
  only 
  approximately 
  

   parallel 
  and 
  perpendicular, 
  except 
  at 
  the 
  very 
  surface. 
  

  

  The 
  term 
  " 
  surface 
  nivellee 
  " 
  used 
  by 
  Lamarck 
  in 
  his 
  description 
  

   of 
  IS. 
  fenestrata 
  well 
  expresses 
  the 
  appearance 
  which 
  the 
  sponge 
  

   has 
  of 
  having 
  been 
  'pared 
  smooth, 
  as 
  in 
  the 
  sj)ccies 
  i/. 
  dcrasa. 
  (see 
  

   Part 
  I., 
  p. 
  382, 
  of 
  this 
  Keport). 
  

  

  It 
  is 
  easy 
  to 
  distinguish 
  among 
  the 
  specimens 
  two 
  varieties, 
  of 
  

   which 
  one 
  apparently 
  corresponds 
  to 
  the 
  more 
  typical 
  form 
  of 
  Hyatt's 
  

   subspecies, 
  and 
  may 
  therefore 
  stand 
  under 
  that 
  name, 
  viz. 
  

  

  Hippospongia 
  sinuosa, 
  var. 
  mauritiana. 
  

  

  The 
  general 
  form 
  of 
  the 
  sponge 
  is 
  that 
  of 
  a 
  low, 
  horizontally 
  ex- 
  

   tended 
  mass, 
  apparently 
  originally 
  attached 
  by 
  one 
  or 
  more 
  small 
  

   points 
  ; 
  it 
  is 
  about 
  35 
  millim. 
  high, 
  and 
  throws 
  out 
  short 
  subcylindri- 
  

   cal, 
  terminally-rounded 
  lobes 
  25-35 
  millim. 
  in 
  diameter. 
  Colour 
  in 
  

   macerated 
  state 
  bright 
  amber-yellow. 
  Diameter 
  of 
  the 
  meandering 
  

   canals 
  of 
  the 
  skeleton 
  2-5 
  to 
  5 
  millim. 
  

  

  The 
  skeleton 
  consists 
  of 
  a 
  strong 
  horizontal 
  system 
  of 
  long 
  secon- 
  

   dary 
  fibres 
  lying 
  parallel 
  to 
  the 
  surface, 
  and 
  of 
  sliort 
  stout, 
  primary 
  

  

  