﻿SPONGUDA. 
  593 
  

  

  regularity 
  and 
  straightness 
  of 
  the 
  primaries, 
  the 
  secondaries 
  more 
  

   constantly 
  form 
  right 
  angles 
  with 
  them, 
  and 
  the 
  meshes 
  are 
  more 
  

   commonly 
  rectangular. 
  (3) 
  The 
  primary 
  fibres 
  are 
  more 
  or 
  less 
  con- 
  

   stantly 
  sand-cored 
  ; 
  the 
  core 
  occupies 
  about 
  half 
  the 
  thickness 
  of 
  the 
  

   fibre. 
  

  

  In 
  the 
  characters 
  of 
  the 
  purely 
  horny 
  fibre 
  and 
  the 
  size 
  of 
  the 
  

   meshes 
  decidua 
  agrees 
  with 
  mauritiana 
  ; 
  the 
  diameter 
  of 
  the 
  fibre 
  

   varies 
  from 
  -025 
  to 
  -063 
  millim. 
  in 
  the 
  specimen 
  examined 
  (i. 
  e. 
  about 
  

   the 
  same 
  range 
  as 
  in 
  mauritiana). 
  

  

  Hah. 
  African 
  Island, 
  Amirante 
  group, 
  from 
  beach. 
  

  

  Distribution. 
  Mauritius, 
  Havana 
  {Hijatt). 
  

  

  It 
  is 
  possible 
  that 
  the 
  forms 
  which 
  I 
  have 
  called 
  varieties 
  should 
  

   rank 
  as 
  distinct 
  species 
  ; 
  but 
  until 
  the 
  arrangement 
  of 
  the 
  soft 
  parts 
  

   is 
  known 
  I 
  prefer 
  to 
  keep 
  them 
  under 
  one 
  specific 
  heading. 
  Younger 
  

   specimens 
  of 
  var. 
  decidua 
  have 
  shallower 
  channels, 
  and 
  one 
  has 
  

   broader 
  tufts 
  and 
  ridges 
  than 
  the 
  rest, 
  thus 
  approaching 
  var. 
  mauri- 
  

   tiana. 
  The 
  distinctness 
  of 
  the 
  two 
  forms, 
  found 
  at 
  precisely 
  the 
  

   same 
  spot, 
  shows 
  that 
  the 
  diff'erences 
  between 
  them 
  cannot 
  be 
  due 
  to 
  

   locality. 
  

  

  4. 
  Phyllospongia 
  papyracea. 
  

  

  Spongia 
  papyracea, 
  £Jsper, 
  Pflanzentli. 
  Fortsetz. 
  ii. 
  p. 
  38, 
  pi. 
  Ixv., 
  

  

  pi. 
  Ixv. 
  A. 
  tigs. 
  1 
  & 
  2. 
  

   Phyllospougia 
  papyracea, 
  Ehlers, 
  Espersch. 
  Spong. 
  p. 
  22 
  (? 
  Hyatt, 
  

  

  Metn. 
  Bost. 
  Soc. 
  ii. 
  p. 
  543, 
  pi. 
  xvii. 
  fig. 
  31). 
  

  

  A 
  dry 
  specimen, 
  195 
  millim. 
  (7f 
  inches) 
  high 
  by 
  155 
  millim. 
  

   (6| 
  in.) 
  in 
  greatest 
  lateral 
  extent. 
  It 
  is 
  proliferous, 
  a 
  single 
  base 
  

   giving 
  rise 
  to 
  the 
  main 
  frond, 
  which 
  is 
  irregularly 
  flabelliform, 
  and 
  

   to 
  a 
  few 
  smaller 
  strip-like 
  fronds, 
  some 
  of 
  which 
  unite 
  with 
  each 
  

   other 
  by 
  their 
  edges 
  at 
  a 
  short 
  distance 
  above 
  the 
  base 
  ; 
  main 
  frond 
  

   also 
  proliferating 
  by 
  giving 
  off" 
  at 
  or 
  near 
  its 
  margin, 
  and 
  in 
  one 
  

   instance 
  from 
  the 
  face, 
  a 
  few 
  small 
  secondary 
  fronds 
  similar 
  in 
  

   character 
  to 
  the 
  smaller 
  fronds 
  which 
  arise 
  from 
  the 
  base. 
  Yents 
  

   few, 
  near 
  margin 
  on 
  both 
  front 
  and 
  back 
  of 
  large 
  fronds, 
  diameter 
  

   1 
  millim. 
  Primary 
  fibres 
  •035-*053 
  millim. 
  in 
  diameter 
  ; 
  secondary 
  

   fibres 
  about 
  "035 
  millim. 
  thick; 
  both 
  devoid 
  of 
  foreign 
  bodies. 
  Some 
  

   minute 
  intermediate 
  fibres 
  or 
  dense 
  strands 
  of 
  sarcode 
  are 
  also 
  pre- 
  

   sent. 
  Meshes 
  of 
  main 
  skeleton 
  about 
  '15 
  miUim. 
  wide, 
  of 
  dermal 
  

   skeleton 
  •18-*28 
  millim. 
  A 
  few 
  scattered 
  foreign 
  bodies 
  in 
  the 
  

   dermal 
  fibres. 
  In 
  other 
  respects 
  it 
  agrees 
  with 
  Espcr's 
  figure, 
  and 
  

   his 
  and 
  Ehlers's 
  descriptions. 
  The 
  latter 
  writer 
  says 
  of 
  the 
  fibres 
  

   of 
  the 
  Esperian 
  specimens 
  that 
  they 
  are 
  " 
  homogeneous," 
  which 
  may 
  

   fairly 
  be 
  taken 
  to 
  imply 
  that, 
  as 
  in 
  this 
  specimen, 
  they 
  contain 
  no 
  

   extraneous 
  matter. 
  Hyatt, 
  however, 
  assigns 
  to 
  this 
  species 
  speci- 
  

   mens 
  (from 
  the 
  Cape 
  of 
  Good 
  Hope) 
  which, 
  from 
  his 
  description, 
  I 
  

   understand 
  to 
  contain 
  a 
  large 
  amount 
  of 
  foreign 
  material 
  in 
  the 
  

   primary 
  fibres. 
  

  

  Hah. 
  Mozambique. 
  

  

  Distribution. 
  Tranquebar 
  {l^spcr). 
  

  

  2ft 
  

  

  