﻿626 
  COLLECTIONS 
  FROM 
  THE 
  WESTERN 
  INDIAN 
  OCEAN. 
  

  

  50. 
  Erylus 
  cylindrigerus 
  *. 
  

   (Plate 
  LIII. 
  fig. 
  M; 
  Plate 
  LIV. 
  figs, 
  e-e""".) 
  

  

  Massive, 
  suberect; 
  terminating 
  above 
  in 
  a 
  lobate 
  prolongation. 
  

   Surface 
  smooth, 
  slightly 
  uneven. 
  Vents 
  one 
  (or 
  more 
  ?) 
  near 
  apex 
  

   of 
  sponge, 
  about 
  2 
  millim. 
  in 
  diameter, 
  opening 
  flush 
  with 
  surface, 
  

   leading 
  obliquely 
  and 
  deeply 
  downwards 
  into 
  sponge. 
  Texture 
  iu 
  

   spirit 
  tough, 
  firm, 
  but 
  somewhat 
  flexible 
  ; 
  colour 
  in 
  spirit 
  dark 
  

   brown, 
  almost 
  black. 
  Skeleton 
  composed 
  of 
  bundles 
  of 
  spicule 
  

   no. 
  1, 
  6-8 
  spicules 
  broad, 
  radiating 
  from 
  centre 
  to 
  just 
  below 
  sur- 
  

   face, 
  "17 
  to 
  "3 
  millim. 
  apart 
  near 
  surface. 
  Surface 
  covered 
  with 
  a 
  

   layer 
  about 
  "1 
  millim. 
  thick 
  of 
  the 
  discoid 
  spicule 
  no. 
  2, 
  arranged 
  

   horizontally. 
  Sarcode 
  subtransparent, 
  very 
  pale 
  brown, 
  almost 
  

   colourless. 
  

  

  Spicules 
  : 
  — 
  (1) 
  Zone-spicules 
  subcylindrical, 
  smooth, 
  straight 
  or 
  

   very 
  slightly 
  and 
  gradually 
  curved, 
  tapering 
  from 
  within 
  about 
  six 
  

   diameters 
  of 
  ends 
  to 
  rounded 
  terminations 
  of 
  about 
  one 
  third 
  the 
  

   diameter 
  of 
  the 
  middle 
  of 
  the 
  shaft 
  ; 
  size 
  about 
  "7 
  by 
  -032 
  millim. 
  

   (2) 
  Discoid, 
  of 
  subdiamond-shaped 
  outliue, 
  viz. 
  that 
  of 
  a 
  rhombus 
  

   with 
  the 
  angles 
  rounded 
  off; 
  length 
  -21 
  to 
  -28 
  millim., 
  breadth 
  

   •1 
  to 
  '14 
  millim., 
  thickness 
  about 
  '04 
  millim. 
  ; 
  covered 
  with 
  minute 
  

   low 
  punctiform 
  spines, 
  about 
  '012 
  millim. 
  apart 
  (spines, 
  as 
  seen 
  

   under 
  a 
  high 
  power 
  from 
  above, 
  stellate 
  in 
  outline 
  ; 
  they 
  are 
  multifid 
  

   terminally). 
  (3) 
  Acerate, 
  smooth, 
  slightly 
  and 
  gradually 
  curved, 
  

   tapering 
  to 
  sharp 
  points 
  from 
  centre 
  ; 
  size 
  '06 
  by 
  -0032 
  millim. 
  

   (scattered 
  abundantly 
  throughout 
  sarcode). 
  (4) 
  Stellate, 
  with 
  about 
  

   10-12 
  straight 
  raj^s 
  -003 
  millim. 
  thick 
  at 
  base, 
  tapering 
  to 
  sharp 
  

   points, 
  springing 
  from 
  a 
  slight 
  central 
  body 
  -01 
  to 
  '013 
  millim. 
  iu 
  

   diameter 
  ; 
  expanse 
  of 
  spicule 
  about 
  'OS 
  millim. 
  (5) 
  Stellate 
  like 
  

   the 
  preceding, 
  but 
  arms 
  about 
  16 
  in 
  number 
  and 
  expanse 
  about 
  

   •02 
  millim. 
  

  

  Bah. 
  Providence 
  Reef, 
  Mascarene 
  group, 
  24 
  fms. 
  ; 
  bottom, 
  sand 
  

   and 
  dead 
  coral. 
  

  

  A 
  single 
  specimen 
  with 
  a 
  somewhat 
  spreading 
  base, 
  which 
  encloses 
  

   calcareous 
  fragments, 
  rising 
  into 
  a 
  subcylindrical, 
  terminally 
  rounded, 
  

   finger-like 
  column, 
  30 
  millim. 
  high 
  and 
  12 
  millim. 
  in 
  mean 
  

   diameter, 
  slightly 
  overgrown 
  by 
  a 
  delicate 
  Sertularian 
  Hydroid; 
  

   extreme 
  diameter 
  of 
  base 
  40 
  miUim. 
  

  

  The 
  species 
  is 
  most 
  closely 
  allied 
  to 
  Stelletta 
  euastrum, 
  Schmidt, 
  

   from 
  Algiers, 
  and 
  to 
  forms 
  so 
  named 
  by 
  Carter 
  (Ann. 
  & 
  Mag. 
  N. 
  H. 
  

   1880, 
  V. 
  pp. 
  135, 
  136) 
  from 
  Ceylon 
  and 
  Australia, 
  which 
  perhaps 
  

   represent 
  another 
  species. 
  Instead 
  of 
  the 
  trifid 
  zone-spicule 
  with 
  

   bifurcate 
  arms 
  found 
  in 
  Schmidt's 
  species, 
  it 
  has 
  simply 
  a 
  subcylin- 
  

   drical 
  spicule, 
  usually 
  blunt 
  at 
  both 
  ends, 
  and 
  wants 
  the 
  long 
  

   slender 
  acerate 
  ; 
  the 
  few-armed 
  stellate 
  has 
  its 
  arms 
  more 
  numerous 
  

   (10-12 
  instead 
  of 
  2-4, 
  which 
  is 
  the 
  range 
  represented 
  by 
  Schmidt's 
  

  

  "^ 
  From 
  the 
  cylindrical 
  zoiie-spicule. 
  

  

  