﻿598 
  COLLECTIONS 
  FROM 
  THE 
  "WESTERN 
  INDIAN 
  OCEAN. 
  

  

  Bowerbank, 
  but 
  differing 
  in 
  its 
  very 
  dense 
  and 
  opaque 
  dermis, 
  and 
  

   the 
  strictly 
  Dysidean 
  distribution 
  of 
  its 
  foreign 
  bodies, 
  viz. 
  only 
  in 
  

   the 
  skeleton-fibres. 
  The 
  primary 
  fibres 
  arc 
  either 
  single 
  or 
  multiple 
  

   in 
  the 
  same 
  conulus, 
  and 
  range 
  from 
  about 
  '07 
  to 
  -36 
  millim. 
  in 
  

   diameter. 
  The 
  sponge 
  forms 
  low, 
  longitudinally-extended 
  masses, 
  

   about 
  50 
  millim. 
  (2 
  inches) 
  in 
  greatest 
  length, 
  12 
  millim. 
  in 
  greatest 
  

   vertical 
  thickness, 
  throwing 
  out 
  rounded 
  lobes 
  which 
  are 
  15 
  millim. 
  

   in 
  greatest 
  diameter. 
  Vents 
  round, 
  few, 
  placed 
  near 
  ends 
  of 
  lobes, 
  

   1 
  to 
  2-5 
  millim. 
  in 
  diameter. 
  Texture 
  in 
  spirit 
  rather 
  elastic, 
  com- 
  

   pressible. 
  Conuli 
  sharp-pointed, 
  usually 
  connected 
  by 
  radiating 
  

   ridges 
  with 
  each 
  other; 
  height 
  '75 
  to 
  1 
  millim., 
  distance 
  apart 
  1-2 
  

   millim. 
  Dermal 
  membrane 
  very 
  dark 
  grey, 
  glabrous. 
  Primary 
  

   fibres, 
  as 
  such, 
  apparently 
  existing 
  only 
  in 
  the 
  conuli, 
  and 
  not 
  ex- 
  

   tending 
  beneath 
  them 
  into 
  the 
  mass 
  of 
  the 
  sponge 
  ; 
  secondary 
  fibres 
  

   also 
  very 
  slightly 
  developed, 
  except 
  in 
  the 
  ridges 
  connecting 
  the 
  

   conuli, 
  where 
  they 
  form 
  a 
  dense 
  network 
  of 
  horizontal 
  fibres, 
  ex- 
  

   tending 
  to 
  a 
  depth 
  of 
  about 
  1 
  millim. 
  below 
  the 
  surface. 
  Skeleton- 
  

   fibres 
  "05 
  to 
  '18 
  millim. 
  thick 
  ; 
  generally 
  compact 
  in 
  structure, 
  

   exhibiting 
  no 
  horny 
  substance 
  to 
  view. 
  

  

  Hab. 
  Mozambique, 
  between 
  tide-marks 
  (on 
  back 
  of 
  crab) 
  ; 
  Provi- 
  

   dence 
  Island, 
  Mascarene 
  group, 
  19 
  fms. 
  (on 
  rock). 
  

  

  Carter's 
  species 
  D. 
  Jcirki, 
  from 
  Mauritius, 
  South 
  Australia, 
  and 
  

   the 
  Cape 
  of 
  Good 
  Hope, 
  above 
  cited, 
  may 
  possibly 
  include 
  this 
  ; 
  but 
  

   as 
  from 
  his 
  description 
  and 
  specimens 
  it 
  is 
  evident 
  that 
  he 
  groups 
  

   more 
  than 
  one 
  species 
  together, 
  and 
  as 
  the 
  present 
  form 
  is 
  decidedly 
  

   distinct 
  from 
  Bowerbank's 
  D. 
  Tcirli 
  (from 
  the 
  far 
  smaller 
  diameter 
  

   of 
  the 
  largest 
  skeleton-fibres), 
  it 
  is 
  not 
  necessary 
  to 
  pursue 
  the 
  

   question 
  further. 
  The 
  very 
  tough 
  and 
  opaque 
  dermal 
  layer 
  and 
  the 
  

   remarkable 
  development 
  of 
  the 
  secondary 
  or 
  horizontal 
  fibre-system, 
  

   which 
  assists 
  in 
  producing 
  it, 
  distinguish 
  this 
  Dysklea 
  from 
  all 
  

   intelligibly 
  described 
  species. 
  Sponrielki 
  elegans, 
  Nardo, 
  as 
  described 
  

   by 
  F. 
  E. 
  Schulze, 
  appears 
  to 
  approach 
  it 
  in 
  the 
  fasciculated 
  arrange- 
  

   ment 
  of 
  the 
  primary 
  fibres, 
  the 
  proportions 
  of 
  the 
  conuli, 
  and 
  the 
  

   general 
  shape, 
  but 
  differs 
  in 
  its 
  pale 
  colour 
  and 
  in 
  having 
  the 
  secon- 
  

   dary 
  fibres 
  more 
  or 
  less 
  free 
  from 
  sand. 
  

  

  OLIGOCERAS. 
  

  

  Schulze, 
  Zeitsch. 
  wiss. 
  Zool. 
  xxxiii, 
  p. 
  34. 
  

  

  This 
  genus, 
  introduced 
  (and 
  rightly, 
  as 
  it 
  seems 
  to 
  me) 
  by 
  Mar- 
  

   shall 
  into 
  this 
  family, 
  is 
  based 
  on 
  a 
  species 
  from 
  the 
  Adriatic, 
  

   remarkable 
  for 
  a 
  habit 
  of 
  attaching 
  to 
  itself 
  foreign 
  bodies 
  of 
  some 
  

   size. 
  Prof. 
  Schulze 
  has 
  expressed 
  to 
  me 
  verbally 
  a 
  doubt 
  as 
  to 
  

   whether 
  the 
  genus 
  will 
  prove 
  to 
  have 
  been 
  rightly 
  established. 
  If, 
  

   however, 
  this 
  is 
  due 
  to 
  the 
  supposition 
  that 
  Oligoceras 
  is 
  a 
  young 
  

   stage 
  of 
  a 
  horny 
  sponge, 
  I 
  think 
  it 
  may 
  be 
  set 
  aside 
  * 
  by 
  a 
  consi- 
  

  

  * 
  Since 
  writing 
  the 
  above, 
  I 
  have 
  been 
  assured 
  by 
  Di*. 
  Polujaeff, 
  whose 
  Report 
  

   on 
  the 
  ' 
  Challenger 
  ' 
  Ceratosa 
  is 
  in 
  the 
  press, 
  that 
  he 
  has 
  found 
  the 
  skeleton 
  of 
  

  

  