﻿SPONGIIDA. 
  471 
  

  

  of 
  that 
  form, 
  in 
  its 
  incrusting 
  habit 
  (purpurea 
  being 
  massive), 
  in 
  

   the 
  inferior 
  diameter 
  of 
  the 
  shaft 
  of 
  the 
  spinulate 
  and 
  the 
  superior 
  

   length 
  of 
  the 
  spinispirular 
  spicule 
  (in 
  p>urpurea 
  these 
  dimensions 
  

   are 
  respectively 
  "OlS 
  and 
  '016 
  raillim.), 
  the 
  latter 
  usually 
  consisting 
  

   in 
  purpurea 
  of 
  only 
  one 
  to 
  one 
  and 
  a 
  half 
  bends. 
  

  

  The 
  single 
  spirit-specimen 
  measures 
  32 
  millim. 
  {\\ 
  inch) 
  in 
  

   height 
  by 
  30 
  millim. 
  in 
  longest 
  diameter, 
  by 
  10 
  millim. 
  (g 
  inch) 
  

   in 
  greatest 
  thickness. 
  

  

  TETRA 
  CTINELLIDA. 
  

  

  The 
  family 
  Lithistidce 
  is 
  not 
  represented. 
  This 
  is 
  not 
  surprising 
  

   if 
  it 
  is 
  remembered 
  that 
  the 
  depths 
  investigated 
  did 
  not 
  exceed 
  40 
  

   fms. 
  Mr. 
  Carter's 
  better 
  fortune 
  with 
  collections 
  from 
  Ceylon 
  is 
  in 
  

   part 
  due 
  to 
  the 
  greater 
  depth 
  at 
  which 
  the 
  specimens 
  were 
  obtained. 
  

  

  CHORISTID^. 
  

   Sollas, 
  Ann. 
  ^ 
  3Ia(j. 
  N. 
  H. 
  1882, 
  ix. 
  p. 
  1G4. 
  

  

  Prof. 
  Sollas 
  has 
  since 
  proposed 
  a 
  diflfcrent 
  arrangement 
  of 
  the 
  

   Tetractinellida, 
  but 
  the 
  division 
  into 
  Choristidae 
  and 
  Lithistida) 
  

   appears 
  a 
  natural 
  and 
  convenient 
  one. 
  Tlie 
  species 
  obtained, 
  

   though 
  few 
  in 
  number, 
  are 
  of 
  remarkable 
  interest, 
  and 
  all 
  new 
  to 
  

   the 
  Australian 
  seas. 
  

  

  STELLETTA, 
  Sclimidt. 
  

  

  This 
  genus, 
  as 
  at 
  present 
  constituted, 
  is 
  decidedly 
  heterogeneous. 
  

   Some 
  of 
  Schmidt's 
  and 
  Carter's 
  species 
  appear 
  referable 
  either 
  to 
  

   Oeodia, 
  or 
  some 
  genus 
  intermediate 
  between 
  Geodia 
  and 
  Stelletta 
  

   (by 
  virtue 
  of 
  the 
  transitional 
  character 
  of 
  their 
  ball-steUate 
  spicule), 
  

   while 
  S. 
  eaastrum 
  appears 
  distinct 
  by 
  virtue 
  of 
  its 
  dlslcs. 
  The 
  more 
  

   typical 
  forms 
  appear 
  to 
  be 
  divisible 
  into 
  subgroups 
  which 
  coincide 
  

   roughly 
  with 
  their 
  geographical 
  distribution. 
  Thus 
  the 
  Atlantic 
  

   species 
  mostly 
  have 
  medium-sized 
  stellates, 
  with 
  numerous 
  rather 
  

   coarse, 
  pointed 
  rays 
  ; 
  the 
  Indo-Pacific 
  ones 
  have 
  few-rayed 
  stellates, 
  

   usually 
  minute 
  ; 
  of 
  the 
  latter, 
  the 
  Fijian 
  and 
  two 
  of 
  the 
  Ceylon 
  

   forms 
  agree 
  in 
  having 
  a 
  small 
  surface 
  bacillate 
  or 
  acerate 
  spicule, 
  

   while 
  one 
  Ceylon 
  form 
  (^S'. 
  tetlujopsis) 
  and 
  all 
  the 
  Australian 
  ones 
  

   known 
  at 
  present 
  agree 
  in 
  having 
  only 
  minute 
  delicate 
  rayed 
  

   stellates. 
  

  

  The 
  Indo-Pacific 
  species 
  of 
  Stelletta, 
  s. 
  str., 
  may 
  be 
  divided 
  into 
  

   two 
  groups 
  : 
  — 
  

  

  Group 
  1. 
  With 
  bacillar 
  or 
  acerate 
  flesh-spicule. 
  

  

  1. 
  S. 
  (Ecionemia) 
  acervus, 
  Bowerbank, 
  P. 
  Z. 
  S. 
  1873, 
  p. 
  322, 
  

   pi. 
  XXX. 
  figs. 
  1-6. 
  Fiji 
  Islands. 
  

  

  2. 
  S. 
  (Ecionemia) 
  densa, 
  id. 
  Z. 
  c. 
  p. 
  322, 
  pi. 
  xxx. 
  figs. 
  7-14. 
  Fiji 
  

   Islands. 
  

  

  3. 
  S. 
  (Tisiphonia) 
  nana. 
  Carter, 
  Ann. 
  & 
  Mag. 
  N. 
  H, 
  1880, 
  v. 
  

   p. 
  138, 
  pi. 
  vii. 
  fig. 
  43. 
  Gulf 
  of 
  Manaar, 
  Ceylon. 
  

  

  